wip why does HSE run at 16MHz?

build/final.elf.map

@@ -53,7 +53,7 @@ Discarded input sections
  .debug_macro   0x00000000       0x89 build/main.o
  .debug_macro   0x00000000      0x4cc build/main.o
  .debug_macro   0x00000000       0x22 build/main.o
- .debug_macro   0x00000000       0x46 build/main.o
+ .debug_macro   0x00000000       0xa0 build/main.o
  .group         0x00000000        0xc build/startup.o
  .group         0x00000000        0xc build/startup.o
  .group         0x00000000        0xc build/startup.o
@@ -128,9 +128,9 @@ Discarded input sections
  .debug_macro   0x00000000      0x1df build/usart.o
  .debug_macro   0x00000000       0x89 build/usart.o
  .debug_macro   0x00000000      0x4cc build/usart.o
- .debug_macro   0x00000000      0x167 build/usart.o
+ .debug_macro   0x00000000      0x191 build/usart.o
  .debug_macro   0x00000000       0x22 build/usart.o
- .debug_macro   0x00000000       0x5e build/usart.o
+ .debug_macro   0x00000000       0x82 build/usart.o
 
 Memory Configuration
 
@@ -157,144 +157,141 @@ LOAD build/usart.o
                 0x08000000                interrupt_vector_table
                 0x08000198                        . = ALIGN (0x4)
 
-.text           0x08000198      0x520
+.text           0x08000198      0x4f8
                 0x08000198                        . = ALIGN (0x4)
  *(.text)
  *(.text.*)
  .text.gpio_set_mode
                 0x08000198       0x62 build/gpio.o
                 0x08000198                gpio_set_mode
- .text.gpio_set_af
-                0x080001fa       0x98 build/gpio.o
-                0x080001fa                gpio_set_af
  .text.gpio_write
-                0x08000292       0x4c build/gpio.o
+                0x080001fa       0x4c build/gpio.o
-                0x08000292                gpio_write
+                0x080001fa                gpio_write
- *fill*         0x080002de        0x2 
+ *fill*         0x08000246        0x2 
  .text.system_clock_init
-                0x080002e0      0x11c build/main.o
+                0x08000248      0x13c build/main.o
- .text.main     0x080003fc       0x9c build/main.o
+ .text.main     0x08000384       0x9c build/main.o
-                0x080003fc                main
+                0x08000384                main
  .text.init_memory
-                0x08000498       0x64 build/startup.o
+                0x08000420       0x64 build/startup.o
-                0x08000498                init_memory
+                0x08000420                init_memory
- .text.reset    0x080004fc       0x10 build/startup.o
+ .text.reset    0x08000484       0x10 build/startup.o
-                0x080004fc                reset
+                0x08000484                reset
  .text.default_handler
-                0x0800050c        0x8 build/startup.o
+                0x08000494        0x8 build/startup.o
-                0x0800050c                exti0
+                0x08000494                exti0
-                0x0800050c                debug_monitor
+                0x08000494                debug_monitor
-                0x0800050c                rcc
+                0x08000494                rcc
-                0x0800050c                x
+                0x08000494                x
-                0x0800050c                sdio
+                0x08000494                sdio
-                0x0800050c                usage_fault
+                0x08000494                usage_fault
-                0x0800050c                tim1_up_tim10
+                0x08000494                tim1_up_tim10
-                0x0800050c                usart1
+                0x08000494                usart1
-                0x0800050c                i2c3_er
+                0x08000494                i2c3_er
-                0x0800050c                spi2
+                0x08000494                spi2
-                0x0800050c                dma1_stream1
+                0x08000494                dma1_stream1
-                0x0800050c                bus_fault
+                0x08000494                bus_fault
-                0x0800050c                spi5
+                0x08000494                spi5
-                0x0800050c                exti3
+                0x08000494                exti3
-                0x0800050c                dma2_stream5
+                0x08000494                dma2_stream5
-                0x0800050c                tim2
+                0x08000494                tim2
-                0x0800050c                dma1_stream6
+                0x08000494                dma1_stream6
-                0x0800050c                default_handler
+                0x08000494                default_handler
-                0x0800050c                i2c1_er
+                0x08000494                i2c1_er
-                0x0800050c                hard_fault
+                0x08000494                hard_fault
-                0x0800050c                usart6
+                0x08000494                usart6
-                0x0800050c                exti15_10
+                0x08000494                exti15_10
-                0x0800050c                usart2
+                0x08000494                usart2
-                0x0800050c                pend_sv
+                0x08000494                pend_sv
-                0x0800050c                i2c1_ev
+                0x08000494                i2c1_ev
-                0x0800050c                wwdg
+                0x08000494                wwdg
-                0x0800050c                adc
+                0x08000494                adc
-                0x0800050c                rtc_alarm
+                0x08000494                rtc_alarm
-                0x0800050c                spi3
+                0x08000494                spi3
-                0x0800050c                exti1
+                0x08000494                exti1
-                0x0800050c                mem_manage
+                0x08000494                mem_manage
-                0x0800050c                dma2_stream1
+                0x08000494                dma2_stream1
-                0x0800050c                dma1_stream2
+                0x08000494                dma1_stream2
-                0x0800050c                dma2_stream3
+                0x08000494                dma2_stream3
-                0x0800050c                sv_call
+                0x08000494                sv_call
-                0x0800050c                tim3
+                0x08000494                tim3
-                0x0800050c                otg_fs
+                0x08000494                otg_fs
-                0x0800050c                dma1_stream5
+                0x08000494                dma1_stream5
-                0x0800050c                dma2_stream6
+                0x08000494                dma2_stream6
-                0x0800050c                flash
+                0x08000494                flash
-                0x0800050c                tamp_stamp
+                0x08000494                tamp_stamp
-                0x0800050c                i2c3_ev
+                0x08000494                i2c3_ev
-                0x0800050c                rtc_wkup
+                0x08000494                rtc_wkup
-                0x0800050c                dma2_stream0
+                0x08000494                dma2_stream0
-                0x0800050c                pvd
+                0x08000494                pvd
-                0x0800050c                fpu
+                0x08000494                fpu
-                0x0800050c                exti4
+                0x08000494                exti4
-                0x0800050c                exti2
+                0x08000494                exti2
-                0x0800050c                spi1
+                0x08000494                spi1
-                0x0800050c                dma1_stream0
+                0x08000494                dma1_stream0
-                0x0800050c                tim1_brk_tim9
+                0x08000494                tim1_brk_tim9
-                0x0800050c                i2c2_ev
+                0x08000494                i2c2_ev
-                0x0800050c                otg_fs_wkup
+                0x08000494                otg_fs_wkup
-                0x0800050c                spi4
+                0x08000494                spi4
-                0x0800050c                dma2_stream2
+                0x08000494                dma2_stream2
-                0x0800050c                tim1_cc
+                0x08000494                tim1_cc
-                0x0800050c                tim1_trg_com_tim11
+                0x08000494                tim1_trg_com_tim11
-                0x0800050c                exti9_5
+                0x08000494                exti9_5
-                0x0800050c                dma1_stream3
+                0x08000494                dma1_stream3
-                0x0800050c                dma2_stream4
+                0x08000494                dma2_stream4
-                0x0800050c                i2c2_er
+                0x08000494                i2c2_er
-                0x0800050c                dma2_stream7
+                0x08000494                dma2_stream7
-                0x0800050c                dma1_stream7
+                0x08000494                dma1_stream7
-                0x0800050c                nmi
+                0x08000494                nmi
-                0x0800050c                systick
+                0x08000494                systick
-                0x0800050c                tim4
+                0x08000494                tim4
-                0x0800050c                tim5
+                0x08000494                tim5
-                0x0800050c                dma1_stream4
+                0x08000494                dma1_stream4
  .text.tim4_init
-                0x08000514       0x40 build/timer.o
+                0x0800049c       0x40 build/timer.o
-                0x08000514                tim4_init
+                0x0800049c                tim4_init
  .text.tim4_start
-                0x08000554       0x20 build/timer.o
+                0x080004dc       0x20 build/timer.o
-                0x08000554                tim4_start
+                0x080004dc                tim4_start
  .text.usart2_init
-                0x08000574       0xb8 build/usart.o
+                0x080004fc      0x114 build/usart.o
-                0x08000574                usart2_init
+                0x080004fc                usart2_init
  .text.usart2_start
-                0x0800062c       0x20 build/usart.o
+                0x08000610       0x20 build/usart.o
-                0x0800062c                usart2_start
+                0x08000610                usart2_start
  .text.usart2_write_byte
-                0x0800064c       0x30 build/usart.o
+                0x08000630       0x30 build/usart.o
-                0x0800064c                usart2_write_byte
+                0x08000630                usart2_write_byte
  .text.usart2_write
-                0x0800067c       0x2a build/usart.o
+                0x08000660       0x2a build/usart.o
-                0x0800067c                usart2_write
+                0x08000660                usart2_write
  *(.rodata)
- *fill*         0x080006a6        0x2 
+ *fill*         0x0800068a        0x2 
- .rodata        0x080006a8        0xf build/main.o
+ .rodata        0x0800068c        0x3 build/main.o
  *(.rodata.*)
-                0x080006b8                        . = ALIGN (0x4)
+                0x08000690                        . = ALIGN (0x4)
- *fill*         0x080006b7        0x1 
+ *fill*         0x0800068f        0x1 
-                0x080006b8                        _data_addr = LOADADDR (.data)
+                0x08000690                        _data_addr = LOADADDR (.data)
 
-.glue_7         0x080006b8        0x0
+.glue_7         0x08000690        0x0
- .glue_7        0x080006b8        0x0 linker stubs
+ .glue_7        0x08000690        0x0 linker stubs
 
-.glue_7t        0x080006b8        0x0
+.glue_7t        0x08000690        0x0
- .glue_7t       0x080006b8        0x0 linker stubs
+ .glue_7t       0x08000690        0x0 linker stubs
 
-.vfp11_veneer   0x080006b8        0x0
+.vfp11_veneer   0x08000690        0x0
- .vfp11_veneer  0x080006b8        0x0 linker stubs
+ .vfp11_veneer  0x08000690        0x0 linker stubs
 
-.v4_bx          0x080006b8        0x0
+.v4_bx          0x08000690        0x0
- .v4_bx         0x080006b8        0x0 linker stubs
+ .v4_bx         0x08000690        0x0 linker stubs
 
-.iplt           0x080006b8        0x0
+.iplt           0x08000690        0x0
- .iplt          0x080006b8        0x0 build/main.o
+ .iplt          0x08000690        0x0 build/main.o
 
-.rel.dyn        0x080006b8        0x0
+.rel.dyn        0x08000690        0x0
- .rel.iplt      0x080006b8        0x0 build/main.o
+ .rel.iplt      0x08000690        0x0 build/main.o
 
-.data           0x20000000        0x0 load address 0x080006b8
+.data           0x20000000        0x0 load address 0x08000690
                 0x20000000                        . = ALIGN (0x4)
                 0x20000000                        _data_start = .
  *(.data)
@@ -302,10 +299,10 @@ LOAD build/usart.o
                 0x20000000                        . = ALIGN (0x4)
                 0x20000000                        _data_end = .
 
-.igot.plt       0x20000000        0x0 load address 0x080006b8
+.igot.plt       0x20000000        0x0 load address 0x08000690
  .igot.plt      0x20000000        0x0 build/main.o
 
-.bss            0x20000000        0x0 load address 0x080006b8
+.bss            0x20000000        0x0 load address 0x08000690
                 0x20000000                        . = ALIGN (0x4)
                 0x20000000                        _bss_start = .
  *(.bss)
@@ -315,46 +312,46 @@ LOAD build/usart.o
 OUTPUT(build/final.elf elf32-littlearm)
 LOAD linker stubs
 
-.debug_info     0x00000000      0xf1e
+.debug_info     0x00000000      0xeb1
- .debug_info    0x00000000      0x262 build/gpio.o
+ .debug_info    0x00000000      0x205 build/gpio.o
- .debug_info    0x00000262      0x47e build/main.o
+ .debug_info    0x00000205      0x47e build/main.o
- .debug_info    0x000006e0      0x188 build/startup.o
+ .debug_info    0x00000683      0x188 build/startup.o
- .debug_info    0x00000868      0x335 build/timer.o
+ .debug_info    0x0000080b      0x335 build/timer.o
- .debug_info    0x00000b9d      0x381 build/usart.o
+ .debug_info    0x00000b40      0x371 build/usart.o
 
-.debug_abbrev   0x00000000      0x5ae
+.debug_abbrev   0x00000000      0x547
- .debug_abbrev  0x00000000      0x11d build/gpio.o
+ .debug_abbrev  0x00000000      0x119 build/gpio.o
- .debug_abbrev  0x0000011d      0x14b build/main.o
+ .debug_abbrev  0x00000119      0x14b build/main.o
- .debug_abbrev  0x00000268      0x127 build/startup.o
+ .debug_abbrev  0x00000264      0x127 build/startup.o
- .debug_abbrev  0x0000038f       0xb5 build/timer.o
+ .debug_abbrev  0x0000038b       0xb5 build/timer.o
- .debug_abbrev  0x00000444      0x16a build/usart.o
+ .debug_abbrev  0x00000440      0x107 build/usart.o
 
-.debug_aranges  0x00000000       0xe8
+.debug_aranges  0x00000000       0xe0
  .debug_aranges
-                0x00000000       0x30 build/gpio.o
+                0x00000000       0x28 build/gpio.o
  .debug_aranges
-                0x00000030       0x28 build/main.o
+                0x00000028       0x28 build/main.o
  .debug_aranges
-                0x00000058       0x30 build/startup.o
+                0x00000050       0x30 build/startup.o
  .debug_aranges
-                0x00000088       0x28 build/timer.o
+                0x00000080       0x28 build/timer.o
  .debug_aranges
-                0x000000b0       0x38 build/usart.o
+                0x000000a8       0x38 build/usart.o
 
 .debug_rnglists
-                0x00000000       0x99
+                0x00000000       0x92
  .debug_rnglists
-                0x00000000       0x20 build/gpio.o
+                0x00000000       0x19 build/gpio.o
  .debug_rnglists
-                0x00000020       0x1b build/main.o
+                0x00000019       0x1b build/main.o
  .debug_rnglists
-                0x0000003b       0x1f build/startup.o
+                0x00000034       0x1f build/startup.o
  .debug_rnglists
-                0x0000005a       0x19 build/timer.o
+                0x00000053       0x19 build/timer.o
  .debug_rnglists
-                0x00000073       0x26 build/usart.o
+                0x0000006c       0x26 build/usart.o
 
-.debug_macro    0x00000000     0x4853
+.debug_macro    0x00000000     0x497f
  .debug_macro   0x00000000      0xb56 build/gpio.o
  .debug_macro   0x00000b56       0x22 build/gpio.o
  .debug_macro   0x00000b78       0x75 build/gpio.o
@@ -369,39 +366,39 @@ LOAD linker stubs
  .debug_macro   0x0000108c       0x89 build/gpio.o
  .debug_macro   0x00001115      0x4cc build/gpio.o
  .debug_macro   0x000015e1       0x22 build/gpio.o
- .debug_macro   0x00001603       0x46 build/gpio.o
+ .debug_macro   0x00001603       0xa0 build/gpio.o
- .debug_macro   0x00001649      0xb89 build/main.o
+ .debug_macro   0x000016a3      0xb89 build/main.o
- .debug_macro   0x000021d2      0x16d build/main.o
+ .debug_macro   0x0000222c      0x197 build/main.o
- .debug_macro   0x0000233f       0x46 build/main.o
+ .debug_macro   0x000023c3       0x46 build/main.o
- .debug_macro   0x00002385       0x2e build/main.o
+ .debug_macro   0x00002409       0x2e build/main.o
- .debug_macro   0x000023b3       0x22 build/main.o
+ .debug_macro   0x00002437       0x22 build/main.o
- .debug_macro   0x000023d5       0x5e build/main.o
+ .debug_macro   0x00002459       0x82 build/main.o
- .debug_macro   0x00002433      0xb02 build/startup.o
+ .debug_macro   0x000024db      0xb02 build/startup.o
- .debug_macro   0x00002f35       0x56 build/startup.o
+ .debug_macro   0x00002fdd       0x56 build/startup.o
- .debug_macro   0x00002f8b       0x51 build/startup.o
+ .debug_macro   0x00003033       0x51 build/startup.o
- .debug_macro   0x00002fdc      0xb5c build/timer.o
+ .debug_macro   0x00003084      0xb5c build/timer.o
- .debug_macro   0x00003b38      0x167 build/timer.o
+ .debug_macro   0x00003be0      0x191 build/timer.o
- .debug_macro   0x00003c9f      0xb74 build/usart.o
+ .debug_macro   0x00003d71      0xb74 build/usart.o
- .debug_macro   0x00004813       0x40 build/usart.o
+ .debug_macro   0x000048e5       0x9a build/usart.o
 
-.debug_line     0x00000000      0x691
+.debug_line     0x00000000      0x677
- .debug_line    0x00000000      0x179 build/gpio.o
+ .debug_line    0x00000000      0x116 build/gpio.o
- .debug_line    0x00000179      0x1d2 build/main.o
+ .debug_line    0x00000116      0x1e8 build/main.o
- .debug_line    0x0000034b       0xea build/startup.o
+ .debug_line    0x000002fe       0xea build/startup.o
- .debug_line    0x00000435       0xdf build/timer.o
+ .debug_line    0x000003e8       0xdf build/timer.o
- .debug_line    0x00000514      0x17d build/usart.o
+ .debug_line    0x000004c7      0x1b0 build/usart.o
 
-.debug_str      0x00000000     0x626f
+.debug_str      0x00000000     0x658b
- .debug_str     0x00000000     0x53d8 build/gpio.o
+ .debug_str     0x00000000     0x5574 build/gpio.o
-                               0x5588 (size before relaxing)
+                               0x571c (size before relaxing)
- .debug_str     0x000053d8      0xdce build/main.o
+ .debug_str     0x00005574      0xf50 build/main.o
-                               0x62e8 (size before relaxing)
+                               0x661c (size before relaxing)
- .debug_str     0x000061a6       0x88 build/startup.o
+ .debug_str     0x000064c4       0x88 build/startup.o
                                0x3cdc (size before relaxing)
- .debug_str     0x0000622e        0xc build/timer.o
+ .debug_str     0x0000654c        0xc build/timer.o
-                               0x5c41 (size before relaxing)
+                               0x5cfb (size before relaxing)
- .debug_str     0x0000623a       0x35 build/usart.o
+ .debug_str     0x00006558       0x33 build/usart.o
-                               0x5fac (size before relaxing)
+                               0x6291 (size before relaxing)
 
 .comment        0x00000000       0x45
  .comment       0x00000000       0x45 build/gpio.o
@@ -442,9 +439,9 @@ LOAD linker stubs
                 0x00000288        0x8 build/usart.o
                                 0x26c (size before relaxing)
 
-.debug_frame    0x00000000      0x234
+.debug_frame    0x00000000      0x208
- .debug_frame   0x00000000       0x88 build/gpio.o
+ .debug_frame   0x00000000       0x60 build/gpio.o
- .debug_frame   0x00000088       0x50 build/main.o
+ .debug_frame   0x00000060       0x50 build/main.o
- .debug_frame   0x000000d8       0x6c build/startup.o
+ .debug_frame   0x000000b0       0x6c build/startup.o
- .debug_frame   0x00000144       0x50 build/timer.o
+ .debug_frame   0x0000011c       0x50 build/timer.o
- .debug_frame   0x00000194       0xa0 build/usart.o
+ .debug_frame   0x0000016c       0x9c build/usart.o

build/gpio.i

@@ -1999,19 +1999,45 @@ struct gpio {
   volatile uint32_t AFRH;
 };
 
+#define GPIOA_BASE_ADDR (0x40020000U)
+#define GPIOA ((struct gpio *) GPIOA_BASE_ADDR)
+
+
+#define GPIO_MODER_AF_MODE (0b10)
+
+#define GPIO_MODER_MODER8_BIT 16
+#define GPIO_MODER_MODER8_MASK (0b11)
+
+#define GPIO_MODER_MODER3_BIT 6
+#define GPIO_MODER_MODER3_MASK (0b11)
+
+#define GPIO_MODER_MODER2_BIT 4
+#define GPIO_MODER_MODER2_MASK (0b11)
+
+
+#define GPIO_AFRH_AFRH8_BIT 0
+#define GPIO_AFRH_AFRH8_MASK (0b1111)
+#define GPIO_AFRH_AFRH8_MCO_1 (0b0000)
+
+
+#define GPIO_AFRL_AFRL3_BIT 12
+#define GPIO_AFRL_AFRL3_MASK (0b1111)
+#define GPIO_AFRL_AFRL3_USART2_RX (0b0111)
+
+#define GPIO_AFRL_AFRL2_BIT 8
+#define GPIO_AFRL_AFRL2_MASK (0b1111)
+#define GPIO_AFRL_AFRL2_USART2_TX (0b0111)
+
+
 
-#define GPIO_AF_MCO_1 (0b0000)
-#define GPIO_AF_USART2_RX (0b0111)
-#define GPIO_AF_USART2_TX (0b0111)
 
 #define GPIO_BASE_ADDR (0x40020000U)
 #define GPIO_PORT_OFFSET (0x400U)
 #define GPIO(port) ((struct gpio*)(uintptr_t)(GPIO_BASE_ADDR + (GPIO_PORT_OFFSET * port)))
 
+#define BIT(x) (1 << x)
 
-#define PORT(port) (((port) - 'A') << 8)
+#define PIN(port,num) ((((port) - 'A') << 8) | num)
-
-#define PIN(port,num) (PORT(port) | num)
 
 #define PINNUM(pin) (pin & 0b1111)
 
@@ -2025,37 +2051,24 @@ typedef enum {
 } GPIO_MODE;
 
 void gpio_set_mode(uint16_t pin, GPIO_MODE mode);
-void gpio_set_af(uint16_t pin, uint8_t af);
 void gpio_write(uint16_t pin, 
-# 47 "src/gpio.h" 3 4
+# 72 "src/gpio.h" 3 4
                              _Bool 
-# 47 "src/gpio.h"
+# 72 "src/gpio.h"
                                   val);
 # 5 "src/gpio.c" 2
 
 void gpio_set_mode(uint16_t pin, GPIO_MODE mode) {
   struct gpio *gpio = ((struct gpio*)(uintptr_t)((0x40020000U) + ((0x400U) * (pin >> 8))));
   int pn = (pin & 0b1111);
-  gpio->MODER &= ~(0b11 << (pn * 2));
+  gpio->MODER &= ~(0x0011 << (pn * 2));
-  gpio->MODER |= (mode & 0b11) << (pn * 2);
+  gpio->MODER |= (mode & 0b011) << (pn * 2);
-}
-
-void gpio_set_af(uint16_t pin, uint8_t af) {
-  struct gpio *gpio = ((struct gpio*)(uintptr_t)((0x40020000U) + ((0x400U) * (pin >> 8))));
-  int pn = (pin & 0b1111);
-  if (pn < 8) {
- gpio->AFRL &= ~(0b1111 << (pn * 4));
- gpio->AFRL |= (af & 0b1111) << (pn * 4);
-  } else {
- gpio->AFRH &= ~(0b1111 << (pn * 4));
- gpio->AFRH |= (af & 0b1111) << (pn * 4);
-  }
 }
 
 void gpio_write(uint16_t pin, 
-# 25 "src/gpio.c" 3 4
+# 13 "src/gpio.c" 3 4
                              _Bool 
-# 25 "src/gpio.c"
+# 13 "src/gpio.c"
                                   val) {
   struct gpio *gpio = ((struct gpio*)(uintptr_t)((0x40020000U) + ((0x400U) * (pin >> 8))));
   gpio->BSRR = (0b0011 << (pin & 0b1111)) << (val ? 0 : 16);

build/main.i

@@ -2029,6 +2029,11 @@ struct rcc {
 #define RCC_CR_PLLON_ON (1 << RCC_CR_PLLON_BIT)
 
 
+#define RCC_CR_CSS_BIT 19
+#define RCC_CR_CSS_ON (1 << RCC_CR_CSS_BIT)
+
+
+
 #define RCC_CR_HSERDY_BIT 17
 #define RCC_CR_HSERDY_READY (1 << RCC_CR_HSERDY_BIT)
 
@@ -2051,6 +2056,7 @@ struct rcc {
 
 #define RCC_PLLCFGR_PLLSRC_BIT 22
 #define RCC_PLLCFGR_PLLSRC_HSE (1 << RCC_PLLCFGR_PLLSRC_BIT)
+#define RCC_PLLCFGR_PLLSRC_HSI (0 << RCC_PLLCFGR_PLLSRC_BIT)
 
 #define RCC_PLLCFGR_PLLP_BIT 16
 #define RCC_PLLCFGR_PLLP_MASK (0b11)
@@ -2070,6 +2076,7 @@ struct rcc {
 #define RCC_CFGR_PPRE_DIV_2 (0b100)
 
 
+#define RCC_CFGR_MCO1_HSI (0b00)
 #define RCC_CFGR_MCO1_HSE (0b10)
 #define RCC_CFGR_MCO1_PLL (0b11)
 
@@ -2077,7 +2084,6 @@ struct rcc {
 #define RCC_CFGR_MCO1_MASK (0b11)
 
 #define RCC_CFGR_MCO1PRE_DIV4 (0b110)
-#define RCC_CFGR_MCO1PRE_DIV2 (0b100)
 
 #define RCC_CFGR_MCO1PRE_BIT 24
 #define RCC_CFGR_MCO1PRE_MASK (0b111)
@@ -2103,6 +2109,7 @@ struct rcc {
 #define RCC_CFGR_SWS_MASK (0b11)
 
 
+#define RCC_CFGR_SW_PLL (0b10)
 #define RCC_CFGR_SW_PLL (0b10)
 
 #define RCC_CFGR_SW_BIT 0
@@ -2110,6 +2117,11 @@ struct rcc {
 #define RCC_CFGR_SW(clock) ((clock & RCC_CFGR_SW_MASK) << RCC_CFGR_SW_BIT)
 
 
+
+#define RCC_AHB1ENR_GPIOAEN_BIT 0
+#define RCC_AHB1ENR_GPIOAEN_ENABLE (1 << RCC_AHB1ENR_GPIOAEN_BIT)
+
+
 #define RCC_APB1ENR_PWREN_BIT 28
 #define RCC_APB1ENR_PWREN_CLOCK_ENABLE (1 << RCC_APB1ENR_PWREN_BIT)
 
@@ -2139,19 +2151,45 @@ struct gpio {
   volatile uint32_t AFRH;
 };
 
+#define GPIOA_BASE_ADDR (0x40020000U)
+#define GPIOA ((struct gpio *) GPIOA_BASE_ADDR)
+
+
+#define GPIO_MODER_AF_MODE (0b10)
+
+#define GPIO_MODER_MODER8_BIT 16
+#define GPIO_MODER_MODER8_MASK (0b11)
+
+#define GPIO_MODER_MODER3_BIT 6
+#define GPIO_MODER_MODER3_MASK (0b11)
+
+#define GPIO_MODER_MODER2_BIT 4
+#define GPIO_MODER_MODER2_MASK (0b11)
+
+
+#define GPIO_AFRH_AFRH8_BIT 0
+#define GPIO_AFRH_AFRH8_MASK (0b1111)
+#define GPIO_AFRH_AFRH8_MCO_1 (0b0000)
+
+
+#define GPIO_AFRL_AFRL3_BIT 12
+#define GPIO_AFRL_AFRL3_MASK (0b1111)
+#define GPIO_AFRL_AFRL3_USART2_RX (0b0111)
+
+#define GPIO_AFRL_AFRL2_BIT 8
+#define GPIO_AFRL_AFRL2_MASK (0b1111)
+#define GPIO_AFRL_AFRL2_USART2_TX (0b0111)
+
+
 
-#define GPIO_AF_MCO_1 (0b0000)
-#define GPIO_AF_USART2_RX (0b0111)
-#define GPIO_AF_USART2_TX (0b0111)
 
 #define GPIO_BASE_ADDR (0x40020000U)
 #define GPIO_PORT_OFFSET (0x400U)
 #define GPIO(port) ((struct gpio*)(uintptr_t)(GPIO_BASE_ADDR + (GPIO_PORT_OFFSET * port)))
 
+#define BIT(x) (1 << x)
 
-#define PORT(port) (((port) - 'A') << 8)
+#define PIN(port,num) ((((port) - 'A') << 8) | num)
-
-#define PIN(port,num) (PORT(port) | num)
 
 #define PINNUM(pin) (pin & 0b1111)
 
@@ -2165,11 +2203,10 @@ typedef enum {
 } GPIO_MODE;
 
 void gpio_set_mode(uint16_t pin, GPIO_MODE mode);
-void gpio_set_af(uint16_t pin, uint8_t af);
 void gpio_write(uint16_t pin, 
-# 47 "src/gpio.h" 3 4
+# 72 "src/gpio.h" 3 4
                              _Bool 
-# 47 "src/gpio.h"
+# 72 "src/gpio.h"
                                   val);
 # 6 "src/main.c" 2
 # 1 "src/flash.h" 1
@@ -2200,7 +2237,7 @@ struct flash {
 #define FLASH_ACR_ICEN_ENABLE (1 <<FLASH_ACR_ICEN_BIT)
 
 
-#define FLASH_ACR_LATENCY_3_WAIT_STATES (0b0011)
+#define FLASH_ACR_LATENCY_3_WAIT_STATES (0x0111)
 
 #define FLASH_ACR_LATENCY_BIT 0
 #define FLASH_ACR_LATENCY_MASK (0b1111)
@@ -2287,11 +2324,24 @@ struct usart {
 
 
 
+#define USART_SR_TXE_BIT 7
+#define USART_SR_TXE_TRANSMITTED (1 << USART_SR_TXE_BIT)
+
+
 #define USART_SR_TC_BIT 6
 #define USART_SR_TC_COMPLETED (1 << USART_SR_TC_BIT)
 
 
 
+#define USART_SR_RXNE_BIT 5
+#define USART_SR_RXNE_READY (1 <<USART_SR_RXNE_BIT)
+
+
+
+#define USART_CR1_OVER8_BIT 15
+#define USART_CR1_OVER8_8 (1 << USART_CR1_OVER8_BIT)
+
+
 #define USART_CR1_UE_BIT 13
 #define USART_CR1_UE_ENABLE (1 << USART_CR1_UE_BIT)
 
@@ -2334,6 +2384,9 @@ static void system_clock_init(void) {
   ((struct rcc *) (0x40023800U))->CR |= (1 << 16);
 
 
+  ((struct rcc *) (0x40023800U))->CR |= (1 << 19);
+
+
 
   while (!(((struct rcc *) (0x40023800U))->CR & (1 << 17)));
 
@@ -2342,6 +2395,7 @@ static void system_clock_init(void) {
   ((struct rcc *) (0x40023800U))->CR &= ~(1 << 24);
 
 
+
   ((struct rcc *) (0x40023800U))->PLLCFGR |= (1 << 22);
 
 
@@ -2369,18 +2423,23 @@ static void system_clock_init(void) {
 
   ((struct flash *) (0x40023C00U))->ACR |= (1 <<10);
   ((struct flash *) (0x40023C00U))->ACR |= (1 <<9);
-
+# 75 "src/main.c"
-
-
-
-
-
-
   ((struct rcc *) (0x40023800U))->CFGR |= (((0b10) & (0b11)) << 0);
 
 
 
   while (((((struct rcc *) (0x40023800U))->CFGR >> 2) & (0b11)) != (0b10));
+
+
+
+  ((struct rcc *) (0x40023800U))->CFGR &= ~((0b11) << 21);
+
+
+  ((struct rcc *) (0x40023800U))->CFGR |= ((0b00) << 21);
+
+
+
+
 }
 
 int main(void) {
@@ -2397,20 +2456,21 @@ int main(void) {
 
   uint16_t counter = ((struct timer *) (0x40000800U))->CNT;
   
-# 90 "src/main.c" 3 4
+# 106 "src/main.c" 3 4
  _Bool 
-# 90 "src/main.c"
+# 106 "src/main.c"
       led_on = 
-# 90 "src/main.c" 3 4
+# 106 "src/main.c" 3 4
                ((_Bool)+0u)
-# 90 "src/main.c"
+# 106 "src/main.c"
                     ;
   while(1) {
+
  if ((((struct timer *) (0x40000800U))->CNT - counter) >= 250) {
   led_on = !led_on;
   gpio_write(led, led_on);
 
-  usart2_write("hello, world!\n");
+ usart2_write("U\n");
 
   counter = ((struct timer *) (0x40000800U))->CNT;
  }

build/timer.i

@@ -2014,6 +2014,11 @@ struct rcc {
 #define RCC_CR_PLLON_ON (1 << RCC_CR_PLLON_BIT)
 
 
+#define RCC_CR_CSS_BIT 19
+#define RCC_CR_CSS_ON (1 << RCC_CR_CSS_BIT)
+
+
+
 #define RCC_CR_HSERDY_BIT 17
 #define RCC_CR_HSERDY_READY (1 << RCC_CR_HSERDY_BIT)
 
@@ -2036,6 +2041,7 @@ struct rcc {
 
 #define RCC_PLLCFGR_PLLSRC_BIT 22
 #define RCC_PLLCFGR_PLLSRC_HSE (1 << RCC_PLLCFGR_PLLSRC_BIT)
+#define RCC_PLLCFGR_PLLSRC_HSI (0 << RCC_PLLCFGR_PLLSRC_BIT)
 
 #define RCC_PLLCFGR_PLLP_BIT 16
 #define RCC_PLLCFGR_PLLP_MASK (0b11)
@@ -2055,6 +2061,7 @@ struct rcc {
 #define RCC_CFGR_PPRE_DIV_2 (0b100)
 
 
+#define RCC_CFGR_MCO1_HSI (0b00)
 #define RCC_CFGR_MCO1_HSE (0b10)
 #define RCC_CFGR_MCO1_PLL (0b11)
 
@@ -2062,7 +2069,6 @@ struct rcc {
 #define RCC_CFGR_MCO1_MASK (0b11)
 
 #define RCC_CFGR_MCO1PRE_DIV4 (0b110)
-#define RCC_CFGR_MCO1PRE_DIV2 (0b100)
 
 #define RCC_CFGR_MCO1PRE_BIT 24
 #define RCC_CFGR_MCO1PRE_MASK (0b111)
@@ -2088,6 +2094,7 @@ struct rcc {
 #define RCC_CFGR_SWS_MASK (0b11)
 
 
+#define RCC_CFGR_SW_PLL (0b10)
 #define RCC_CFGR_SW_PLL (0b10)
 
 #define RCC_CFGR_SW_BIT 0
@@ -2095,6 +2102,11 @@ struct rcc {
 #define RCC_CFGR_SW(clock) ((clock & RCC_CFGR_SW_MASK) << RCC_CFGR_SW_BIT)
 
 
+
+#define RCC_AHB1ENR_GPIOAEN_BIT 0
+#define RCC_AHB1ENR_GPIOAEN_ENABLE (1 << RCC_AHB1ENR_GPIOAEN_BIT)
+
+
 #define RCC_APB1ENR_PWREN_BIT 28
 #define RCC_APB1ENR_PWREN_CLOCK_ENABLE (1 << RCC_APB1ENR_PWREN_BIT)
 
@@ -2153,7 +2165,7 @@ void tim4_init(void) {
 
 
 
-  ((struct timer *) (0x40000800U))->PSC = (uint16_t) 96000 - 1;
+  ((struct timer *) (0x40000800U))->PSC = (uint16_t) 48000 - 1;
 
 
   ((struct timer *) (0x40000800U))->ARR = (uint16_t) 0xFFFF;

build/usart.i

@@ -2014,6 +2014,11 @@ struct rcc {
 #define RCC_CR_PLLON_ON (1 << RCC_CR_PLLON_BIT)
 
 
+#define RCC_CR_CSS_BIT 19
+#define RCC_CR_CSS_ON (1 << RCC_CR_CSS_BIT)
+
+
+
 #define RCC_CR_HSERDY_BIT 17
 #define RCC_CR_HSERDY_READY (1 << RCC_CR_HSERDY_BIT)
 
@@ -2036,6 +2041,7 @@ struct rcc {
 
 #define RCC_PLLCFGR_PLLSRC_BIT 22
 #define RCC_PLLCFGR_PLLSRC_HSE (1 << RCC_PLLCFGR_PLLSRC_BIT)
+#define RCC_PLLCFGR_PLLSRC_HSI (0 << RCC_PLLCFGR_PLLSRC_BIT)
 
 #define RCC_PLLCFGR_PLLP_BIT 16
 #define RCC_PLLCFGR_PLLP_MASK (0b11)
@@ -2055,6 +2061,7 @@ struct rcc {
 #define RCC_CFGR_PPRE_DIV_2 (0b100)
 
 
+#define RCC_CFGR_MCO1_HSI (0b00)
 #define RCC_CFGR_MCO1_HSE (0b10)
 #define RCC_CFGR_MCO1_PLL (0b11)
 
@@ -2062,7 +2069,6 @@ struct rcc {
 #define RCC_CFGR_MCO1_MASK (0b11)
 
 #define RCC_CFGR_MCO1PRE_DIV4 (0b110)
-#define RCC_CFGR_MCO1PRE_DIV2 (0b100)
 
 #define RCC_CFGR_MCO1PRE_BIT 24
 #define RCC_CFGR_MCO1PRE_MASK (0b111)
@@ -2088,6 +2094,7 @@ struct rcc {
 #define RCC_CFGR_SWS_MASK (0b11)
 
 
+#define RCC_CFGR_SW_PLL (0b10)
 #define RCC_CFGR_SW_PLL (0b10)
 
 #define RCC_CFGR_SW_BIT 0
@@ -2095,6 +2102,11 @@ struct rcc {
 #define RCC_CFGR_SW(clock) ((clock & RCC_CFGR_SW_MASK) << RCC_CFGR_SW_BIT)
 
 
+
+#define RCC_AHB1ENR_GPIOAEN_BIT 0
+#define RCC_AHB1ENR_GPIOAEN_ENABLE (1 << RCC_AHB1ENR_GPIOAEN_BIT)
+
+
 #define RCC_APB1ENR_PWREN_BIT 28
 #define RCC_APB1ENR_PWREN_CLOCK_ENABLE (1 << RCC_APB1ENR_PWREN_BIT)
 
@@ -2136,19 +2148,45 @@ struct gpio {
   volatile uint32_t AFRH;
 };
 
+#define GPIOA_BASE_ADDR (0x40020000U)
+#define GPIOA ((struct gpio *) GPIOA_BASE_ADDR)
+
+
+#define GPIO_MODER_AF_MODE (0b10)
+
+#define GPIO_MODER_MODER8_BIT 16
+#define GPIO_MODER_MODER8_MASK (0b11)
+
+#define GPIO_MODER_MODER3_BIT 6
+#define GPIO_MODER_MODER3_MASK (0b11)
+
+#define GPIO_MODER_MODER2_BIT 4
+#define GPIO_MODER_MODER2_MASK (0b11)
+
+
+#define GPIO_AFRH_AFRH8_BIT 0
+#define GPIO_AFRH_AFRH8_MASK (0b1111)
+#define GPIO_AFRH_AFRH8_MCO_1 (0b0000)
+
+
+#define GPIO_AFRL_AFRL3_BIT 12
+#define GPIO_AFRL_AFRL3_MASK (0b1111)
+#define GPIO_AFRL_AFRL3_USART2_RX (0b0111)
+
+#define GPIO_AFRL_AFRL2_BIT 8
+#define GPIO_AFRL_AFRL2_MASK (0b1111)
+#define GPIO_AFRL_AFRL2_USART2_TX (0b0111)
+
+
 
-#define GPIO_AF_MCO_1 (0b0000)
-#define GPIO_AF_USART2_RX (0b0111)
-#define GPIO_AF_USART2_TX (0b0111)
 
 #define GPIO_BASE_ADDR (0x40020000U)
 #define GPIO_PORT_OFFSET (0x400U)
 #define GPIO(port) ((struct gpio*)(uintptr_t)(GPIO_BASE_ADDR + (GPIO_PORT_OFFSET * port)))
 
+#define BIT(x) (1 << x)
 
-#define PORT(port) (((port) - 'A') << 8)
+#define PIN(port,num) ((((port) - 'A') << 8) | num)
-
-#define PIN(port,num) (PORT(port) | num)
 
 #define PINNUM(pin) (pin & 0b1111)
 
@@ -2162,11 +2200,10 @@ typedef enum {
 } GPIO_MODE;
 
 void gpio_set_mode(uint16_t pin, GPIO_MODE mode);
-void gpio_set_af(uint16_t pin, uint8_t af);
 void gpio_write(uint16_t pin, 
-# 47 "src/gpio.h" 3 4
+# 72 "src/gpio.h" 3 4
                              _Bool 
-# 47 "src/gpio.h"
+# 72 "src/gpio.h"
                                   val);
 # 3 "src/usart.c" 2
 # 1 "src/usart.h" 1
@@ -2190,11 +2227,24 @@ struct usart {
 
 
 
+#define USART_SR_TXE_BIT 7
+#define USART_SR_TXE_TRANSMITTED (1 << USART_SR_TXE_BIT)
+
+
 #define USART_SR_TC_BIT 6
 #define USART_SR_TC_COMPLETED (1 << USART_SR_TC_BIT)
 
 
 
+#define USART_SR_RXNE_BIT 5
+#define USART_SR_RXNE_READY (1 <<USART_SR_RXNE_BIT)
+
+
+
+#define USART_CR1_OVER8_BIT 15
+#define USART_CR1_OVER8_8 (1 << USART_CR1_OVER8_BIT)
+
+
 #define USART_CR1_UE_BIT 13
 #define USART_CR1_UE_ENABLE (1 << USART_CR1_UE_BIT)
 
@@ -2222,28 +2272,41 @@ void usart2_write(char *buf);
 
 void usart2_init(void) {
 
-  ((struct rcc *) (0x40023800U))->AHB1ENR |= (1 << ((('A') - 'A') << 8));
+  ((struct rcc *) (0x40023800U))->AHB1ENR |= (1 << 0);
 
 
-  uint16_t txPin = (((('A') - 'A') << 8) | 2);
-  gpio_set_mode(txPin, GPIO_MODE_AF);
-  gpio_set_af(txPin, (0b0111));
 
-  uint16_t rxPin = (((('A') - 'A') << 8) | 3);
+  ((struct gpio *) (0x40020000U))->MODER &= ~((0b11) << 4);
-  gpio_set_mode(rxPin, GPIO_MODE_AF);
+  ((struct gpio *) (0x40020000U))->MODER |= ((0b10) << 4);
-  gpio_set_af(rxPin, (0b0111));
+  ((struct gpio *) (0x40020000U))->MODER &= ~((0b11) << 6);
-# 29 "src/usart.c"
+  ((struct gpio *) (0x40020000U))->MODER |= ((0b10) << 6);
+
+
+  ((struct gpio *) (0x40020000U))->AFRL &= ~((0b1111) << 8);
+  ((struct gpio *) (0x40020000U))->AFRL |= ((0b0111) << 8);
+  ((struct gpio *) (0x40020000U))->AFRL &= ~((0b1111) << 12);
+  ((struct gpio *) (0x40020000U))->AFRL |= ((0b0111) << 12);
+
+
+  ((struct gpio *) (0x40020000U))->MODER &= ~((0b11) << 16);
+  ((struct gpio *) (0x40020000U))->MODER |= ((0b10) << 16);
+
+
+  ((struct gpio *) (0x40020000U))->AFRH &= ~((0b1111) << 0);
+  ((struct gpio *) (0x40020000U))->AFRH |= ((0b0000) << 0);
+
+
   ((struct rcc *) (0x40023800U))->APB1ENR |= (1 << 17);
 
 
   ((struct usart *) (0x40004400U))->CR1 = 0;
   ((struct usart *) (0x40004400U))->CR2 = 0;
   ((struct usart *) (0x40004400U))->CR3 = 0;
-# 52 "src/usart.c"
+# 55 "src/usart.c"
   ((struct usart *) (0x40004400U))->BRR &= ~((0b111111111111) << 4);
-  ((struct usart *) (0x40004400U))->BRR |= (0x1A << 4);
+  ((struct usart *) (0x40004400U))->BRR |= (0x68 << 4);
-  ((struct usart *) (0x40004400U))->BRR &= ~((0b111) << 0);
+
-  ((struct usart *) (0x40004400U))->BRR |= (0x0 << 4);
+  ((struct usart *) (0x40004400U))->BRR |= (0x2AB << 0);
 
 
   ((struct usart *) (0x40004400U))->CR1 |= (1 << 3);
@@ -2255,9 +2318,11 @@ void usart2_start(void) {
 }
 
 void usart2_write_byte(uint8_t c) {
+
   ((struct usart *) (0x40004400U))->DR = c;
 
 
+
   while (!(((struct usart *) (0x40004400U))->SR & (1 << 6)));
 }
 

flake.nix

@@ -32,8 +32,8 @@
               pkgs.stlink
               pkgs.gdb
               pkgs.openocd
-              pkgs.gdbgui
               pkgs.stm32cubemx
+              pkgs.gdbgui
             ];
           };
         }

src/flash.h

@@ -25,7 +25,7 @@ struct flash {
 #define FLASH_ACR_ICEN_ENABLE (1 <<FLASH_ACR_ICEN_BIT)
 
 // Latency
-#define FLASH_ACR_LATENCY_3_WAIT_STATES (0b0011)
+#define FLASH_ACR_LATENCY_3_WAIT_STATES (0x0111)
 
 #define FLASH_ACR_LATENCY_BIT 0 // Bits [3:0]
 #define FLASH_ACR_LATENCY_MASK (0b1111)

src/gpio.c

@@ -6,20 +6,8 @@
 void gpio_set_mode(uint16_t pin, GPIO_MODE mode) {
   struct gpio *gpio = GPIO(PINPORT(pin));     // GPIO port address
   int pn = PINNUM(pin);                       // Pin number
-  gpio->MODER &= ~(0b11 << (pn * 2));         // Clear existing setting. Each pin uses 2 bits
+  gpio->MODER &= ~(0x0011 << (pn * 2));       // Clear existing setting. Each pin uses 2 bits
-  gpio->MODER |= (mode & 0b11) << (pn * 2);   // Set new mode. Each pin uses 2 bits
+  gpio->MODER |= (mode & 0b011) << (pn * 2);  // Set new mode. Each pin uses 2 bits
-}
-
-void gpio_set_af(uint16_t pin, uint8_t af) {
-  struct gpio *gpio = GPIO(PINPORT(pin));
-  int pn = PINNUM(pin);
-  if (pn < 8) {
-	gpio->AFRL &= ~(0b1111 << (pn * 4)); // Each pin uses 4 bits
-	gpio->AFRL |= (af & 0b1111) << (pn * 4);
-  } else {
-	gpio->AFRH &= ~(0b1111 << (pn * 4)); // Each pin uses 4 bits
-	gpio->AFRH |= (af & 0b1111) << (pn * 4);
-  }
 }
 
 void gpio_write(uint16_t pin, bool val) {

src/gpio.h

@@ -17,19 +17,45 @@ struct gpio {
   volatile uint32_t AFRH;     // Alternative function high register
 };
 
-// AFRH, AFRL registers
+#define GPIOA_BASE_ADDR (0x40020000U)
-#define GPIO_AF_MCO_1 (0b0000)     // Alternative function 0 (AF0)
+#define GPIOA ((struct gpio *) GPIOA_BASE_ADDR)
-#define GPIO_AF_USART2_RX (0b0111) // Alternative function 7 (AF7)
-#define GPIO_AF_USART2_TX (0b0111) // Alternative function 7 (AF7)
 
+// MODER register
+#define  GPIO_MODER_AF_MODE (0b10)
+
+#define GPIO_MODER_MODER8_BIT 16 // Bits [17:16]
+#define GPIO_MODER_MODER8_MASK (0b11)
+
+#define GPIO_MODER_MODER3_BIT 6 // Bits [7:6]
+#define GPIO_MODER_MODER3_MASK (0b11)
+
+#define GPIO_MODER_MODER2_BIT 4 // Bits [5:4]
+#define GPIO_MODER_MODER2_MASK (0b11)
+
+// AFRH register
+#define GPIO_AFRH_AFRH8_BIT 0 // Bits [3:0]
+#define GPIO_AFRH_AFRH8_MASK (0b1111)
+#define GPIO_AFRH_AFRH8_MCO_1 (0b0000) // Alternative function 0 (AF0)
+
+// AFRL register
+#define GPIO_AFRL_AFRL3_BIT 12 // Bits [15:12]
+#define GPIO_AFRL_AFRL3_MASK (0b1111)
+#define GPIO_AFRL_AFRL3_USART2_RX (0b0111) // Alternative function 7 (AF7)
+
+#define GPIO_AFRL_AFRL2_BIT 8 // Bits [11:8]
+#define GPIO_AFRL_AFRL2_MASK (0b1111)
+#define GPIO_AFRL_AFRL2_USART2_TX (0b0111) // Alternative function 7 (AF7)
+
+
+
+// TODO did I intend to remove GPIO, BIT, PIN etc below with GPIOA, GPIOB etc?
 #define GPIO_BASE_ADDR (0x40020000U)
 #define GPIO_PORT_OFFSET (0x400U)
 #define GPIO(port) ((struct gpio*)(uintptr_t)(GPIO_BASE_ADDR + (GPIO_PORT_OFFSET * port)))
 
-// Create a 8bit number from a port
+#define BIT(x) (1 << x)
-#define PORT(port) (((port) - 'A') << 8)
 // Create a 16bit number from a port and pin
-#define PIN(port, num) (PORT(port) | num)
+#define PIN(port, num) ((((port) - 'A') << 8) | num)
 // get the lower byte from a PIN
 #define PINNUM(pin) (pin & 0b1111)
 // get the upper byte from a PIN
@@ -43,7 +69,6 @@ typedef enum {
 } GPIO_MODE;
 
 void gpio_set_mode(uint16_t pin, GPIO_MODE mode);
-void gpio_set_af(uint16_t pin, uint8_t af);
 void gpio_write(uint16_t pin, bool val);
 
 #endif

src/main.c

@@ -24,6 +24,9 @@ static void system_clock_init(void) {
   // Turn on HSE
   RCC->CR |= RCC_CR_HSEON_ON;
 
+  // Turn on clock security system
+  RCC->CR |= RCC_CR_CSS_ON;
+
   // Wait indefinitely for HSE to be ready
   // TODO indicate error/timeout somehow?
   while (!(RCC->CR & RCC_CR_HSERDY_READY));
@@ -33,6 +36,7 @@ static void system_clock_init(void) {
   RCC->CR &= ~RCC_CR_PLLON_ON;
 
   // Set HSE as PLL source
+  /* RCC->PLLCFGR |= RCC_PLLCFGR_PLLSRC_HSE; */
   RCC->PLLCFGR |= RCC_PLLCFGR_PLLSRC_HSE;
 
   // Settings to achieve system clock of 96Mhz
@@ -61,17 +65,29 @@ static void system_clock_init(void) {
   FLASH->ACR |= FLASH_ACR_DCEN_ENABLE;
   FLASH->ACR |= FLASH_ACR_ICEN_ENABLE;
 
-  // TODO breaks with these flash settings on; turning off for now
   // Set latency to be 3 wait states (TODO: understand why exactly 3)
   /* FLASH->ACR &= ~(FLASH_ACR_LATENCY_MASK << FLASH_ACR_LATENCY_BIT); */
   /* RCC->CFGR |= (FLASH_ACR_LATENCY_3_WAIT_STATES << FLASH_ACR_LATENCY_BIT); */
 
   // Use PLL as system clock
+  /* RCC->CFGR &= ~(RCC_CFGR_SW_MASK << RCC_CFGR_SW_BIT); */
+  /* RCC->CFGR |= (RCC_CFGR_SW_PLL << RCC_CFGR_SW_BIT); */
   RCC->CFGR |= RCC_CFGR_SW(RCC_CFGR_SW_PLL);
 
   // Wait indefinitely for PLL clock to be selected
   // TODO indicate error/timeout somehow?
   while (((RCC->CFGR >> RCC_CFGR_SWS_BIT) & RCC_CFGR_SWS_MASK) != RCC_CFGR_SWS_PLL);
+
+
+  // Output HSE clock
+  RCC->CFGR &= ~(RCC_CFGR_MCO1_MASK << RCC_CFGR_MCO1_BIT);
+  /* RCC->CFGR |= (RCC_CFGR_MCO1_HSE << RCC_CFGR_MCO1_BIT); */
+  /* RCC->CFGR |= (RCC_CFGR_MCO1_PLL << RCC_CFGR_MCO1_BIT); */
+  RCC->CFGR |= (RCC_CFGR_MCO1_HSI << RCC_CFGR_MCO1_BIT);
+
+  /* RCC->CFGR &= ~(RCC_CFGR_MCO1PRE_MASK << RCC_CFGR_MCO1PRE_BIT); */
+  /* RCC->CFGR |= (RCC_CFGR_MCO1PRE_DIV4 << RCC_CFGR_MCO1PRE_BIT); */
+
 }
 
 int main(void) {
@@ -83,17 +99,18 @@ int main(void) {
   (void) usart2_start();
 
   uint16_t led = PIN('C', 13);           // Blue LED
-  RCC->AHB1ENR |= (1 << PINPORT(led));   // Enable GPIO clock for LED
+  RCC->AHB1ENR |= BIT(PINPORT(led));     // Enable GPIO clock for LED
   gpio_set_mode(led, GPIO_MODE_OUTPUT);  // Set blue LED to output mode
 
   uint16_t counter = TIM4->CNT;
   bool led_on = false;
   while(1) {
+	/* usart2_write("U\n"); */
 	if ((TIM4->CNT - counter) >= 250) {
 	 led_on = !led_on;
 	 gpio_write(led, led_on);
 
-	 usart2_write("hello, world!\n");
+	usart2_write("U\n");
 
 	 counter = TIM4->CNT;
 	}

src/rcc.h

@@ -46,6 +46,11 @@ struct rcc {
 #define RCC_CR_PLLON_BIT 24
 #define RCC_CR_PLLON_ON  (1 << RCC_CR_PLLON_BIT)
 
+// Clock security system
+#define RCC_CR_CSS_BIT 19
+#define RCC_CR_CSS_ON (1 << RCC_CR_CSS_BIT)
+
+
 // HSE clock ready flag
 #define RCC_CR_HSERDY_BIT 17
 #define RCC_CR_HSERDY_READY (1 << RCC_CR_HSERDY_BIT)
@@ -69,6 +74,7 @@ struct rcc {
 
 #define RCC_PLLCFGR_PLLSRC_BIT 22
 #define RCC_PLLCFGR_PLLSRC_HSE (1 << RCC_PLLCFGR_PLLSRC_BIT)
+#define RCC_PLLCFGR_PLLSRC_HSI (0 << RCC_PLLCFGR_PLLSRC_BIT)
 
 #define RCC_PLLCFGR_PLLP_BIT 16 // Bits [17:16]
 #define RCC_PLLCFGR_PLLP_MASK (0b11)
@@ -88,6 +94,7 @@ struct rcc {
 #define RCC_CFGR_PPRE_DIV_2	(0b100)
 
 // Microcontroller clock output 1
+#define RCC_CFGR_MCO1_HSI (0b00)
 #define RCC_CFGR_MCO1_HSE (0b10)
 #define RCC_CFGR_MCO1_PLL (0b11)
 
@@ -95,7 +102,6 @@ struct rcc {
 #define RCC_CFGR_MCO1_MASK (0b11)
 
 #define RCC_CFGR_MCO1PRE_DIV4 (0b110)
-#define RCC_CFGR_MCO1PRE_DIV2 (0b100)
 
 #define RCC_CFGR_MCO1PRE_BIT 24 // Bits [26:24]
 #define RCC_CFGR_MCO1PRE_MASK (0b111)
@@ -122,11 +128,17 @@ struct rcc {
 
 // System clock switch
 #define RCC_CFGR_SW_PLL (0b10)
+#define RCC_CFGR_SW_PLL (0b10)
 
 #define RCC_CFGR_SW_BIT 0 // Bits [1:0]
 #define RCC_CFGR_SW_MASK (0b11)
 #define RCC_CFGR_SW(clock) ((clock & RCC_CFGR_SW_MASK) << RCC_CFGR_SW_BIT)
 
+// AHB1ENR Register
+// GPIOA AHB1ENR
+#define RCC_AHB1ENR_GPIOAEN_BIT 0
+#define RCC_AHB1ENR_GPIOAEN_ENABLE (1 << RCC_AHB1ENR_GPIOAEN_BIT)
+
 // APB1ENR Register
 #define RCC_APB1ENR_PWREN_BIT 28
 #define RCC_APB1ENR_PWREN_CLOCK_ENABLE (1 << RCC_APB1ENR_PWREN_BIT)

src/timer.c

@@ -10,8 +10,8 @@ void tim4_init(void) {
   TIM4->CR2 = 0x0000;
 
   // Set prescaler
-  // f_clk = 96MHz -> 96E6/96E3 = 1E3 = 1KHz counting frequency = 1ms
+  // f_clk = 48MHz -> /48000 = 1KHz counting frequency = 1ms
-  TIM4->PSC = (uint16_t) 96000 - 1;
+  TIM4->PSC = (uint16_t) 48000 - 1;
 
   // Set ARR to maximum value to get 1ms between updates
   TIM4->ARR = (uint16_t) 0xFFFF;

src/usart.c

@@ -3,27 +3,29 @@
 #include "usart.h"
 
 void usart2_init(void) {
-  // Enable clock for GPIOA as USART2 is on PORT A pins
+  // Enable clock for GPIOA
-  RCC->AHB1ENR |= (1 << PORT('A'));
+  RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN_ENABLE;
 
   // Configure PA2 and PA3 (USART2 pins) to use alternative functions
-  uint16_t txPin = PIN('A', 2);
+  // file:///home/alex/sync/org/stm32-sand/stm32f411ce.pdf#page=48
-  gpio_set_mode(txPin, GPIO_MODE_AF);
+  GPIOA->MODER &= ~(GPIO_MODER_MODER2_MASK << GPIO_MODER_MODER2_BIT);
-  gpio_set_af(txPin, GPIO_AF_USART2_TX);
+  GPIOA->MODER |= (GPIO_MODER_AF_MODE << GPIO_MODER_MODER2_BIT);
+  GPIOA->MODER &= ~(GPIO_MODER_MODER3_MASK << GPIO_MODER_MODER3_BIT);
+  GPIOA->MODER |= (GPIO_MODER_AF_MODE << GPIO_MODER_MODER3_BIT);
 
-  uint16_t rxPin = PIN('A', 3);
+  // Set pin alternative modes to use USART
-  gpio_set_mode(rxPin, GPIO_MODE_AF);
+  GPIOA->AFRL &= ~(GPIO_AFRL_AFRL2_MASK << GPIO_AFRL_AFRL2_BIT);
-  gpio_set_af(rxPin, GPIO_AF_USART2_RX);
+  GPIOA->AFRL |= (GPIO_AFRL_AFRL2_USART2_TX << GPIO_AFRL_AFRL2_BIT);
+  GPIOA->AFRL &= ~(GPIO_AFRL_AFRL3_MASK << GPIO_AFRL_AFRL3_BIT);
+  GPIOA->AFRL |= (GPIO_AFRL_AFRL3_USART2_RX << GPIO_AFRL_AFRL3_BIT);
 
-  // Enable MC01; for debugging
+  // Configure PA8 to output HSE (MCO1)
-  /* uint16_t clockOutPin = PIN('A', 8); */
+  GPIOA->MODER &= ~(GPIO_MODER_MODER8_MASK << GPIO_MODER_MODER8_BIT);
-  /* gpio_set_mode(clockOutPin, GPIO_MODE_AF); */
+  GPIOA->MODER |= (GPIO_MODER_AF_MODE << GPIO_MODER_MODER8_BIT);
-  /* gpio_set_af(clockOutPin, GPIO_AF_MCO_1); */
+
-  /* RCC->CFGR &= ~(RCC_CFGR_MCO1_MASK << RCC_CFGR_MCO1_BIT); */
+  // Set pin alternative mode to use MCO1
-  /* RCC->CFGR |= (RCC_CFGR_MCO1_HSE << RCC_CFGR_MCO1_BIT); */
+  GPIOA->AFRH &= ~(GPIO_AFRH_AFRH8_MASK << GPIO_AFRH_AFRH8_BIT);
-  /* RCC->CFGR |= (RCC_CFGR_MCO1_PLL << RCC_CFGR_MCO1_BIT); */
+  GPIOA->AFRH |= (GPIO_AFRH_AFRH8_MCO_1 << GPIO_AFRH_AFRH8_BIT);
-  /* RCC->CFGR &= ~(RCC_CFGR_MCO1PRE_MASK << RCC_CFGR_MCO1PRE_BIT); */
-  /* RCC->CFGR |= (RCC_CFGR_MCO1PRE_DIV4 << RCC_CFGR_MCO1PRE_BIT); */
 
   // Enable USART
   RCC->APB1ENR |= RCC_APB1ENR_USART2EN_ENABLE;
@@ -40,19 +42,20 @@ void usart2_init(void) {
   // USARTDIV = (f_clock / (baud * (8 * (2 - OVER8)))
 
   // Target Baud rate = 115200, f_clock = 48MHz,OVER8 = 0
-  // USARTDIV = 48E6 / (115200 * 8 * 2) = 26.0416666
+
-  // mantissa = 26 = 0x1A
+  // USARTDIV = (48E6 / (115200 * (8 * 2))) = 26.0416666
+  // mantissa = 26
   // fraction = 0.041666 * 16 = 0.666656 ~= 1
 
   // baud = 48E6 / (8 * 2 * 26) = 115384.61538461539
-  // error of 0.16% (115384.61538461539 / 115200 ) = 1.001602564102564
+  // error of 0.001% (115384.61538461539 / 115200 ) = 1.001602564102564
-  //
+
-  // skipping fractional part as error rate is good.
+  /* USART2->CR1 |= USART_CR1_OVER8_8; */
 
   USART2->BRR &= ~(USART_BRR_MANTISSA_MASK << USART_BRR_MANTISSA_BIT);
-  USART2->BRR |= (0x1A << USART_BRR_MANTISSA_BIT);
+  USART2->BRR |= (0x68 << USART_BRR_MANTISSA_BIT);
-  USART2->BRR &= ~(USART_BRR_FRACTION_MASK << USART_BRR_FRACTION_BIT);
+  /* USART2->BRR &= ~(USART_BRR_FRACTION_MASK << USART_BRR_FRACTION_BIT); */
-  USART2->BRR |= (0x0 << USART_BRR_MANTISSA_BIT);
+  USART2->BRR |= (0x2AB << USART_BRR_FRACTION_BIT);
 
   // Enable transmitter and receiver
   USART2->CR1 |= USART_CR1_TE_ENABLE;
@@ -64,9 +67,11 @@ void usart2_start(void) {
 }
 
 void usart2_write_byte(uint8_t c) {
+  // Send data
   USART2->DR = c;
 
   // Wait indefinitely for transmission to be ready for data
+  /* while ((USART2->SR & USART_SR_TXE_TRANSMITTED) == 0); */
   while (!(USART2->SR & USART_SR_TC_COMPLETED));
 }
 

src/usart.h

@@ -10,18 +10,31 @@ struct usart {
   volatile uint32_t CR1;  // Control register 1
   volatile uint32_t CR2;  // Control register 2
   volatile uint32_t CR3;  // Control register 3
-  volatile uint32_t GTPR; // Guard time and prescaler register
+  volatile uint32_t GTPR; // Guard time and prescaler registe
 };
 
 #define USART2_BASE_ADDR (0x40004400U)
 #define USART2 ((struct usart *) USART2_BASE_ADDR)
 
 // SR Register
+// Transmission data register empty
+#define USART_SR_TXE_BIT 7
+#define USART_SR_TXE_TRANSMITTED (1 << USART_SR_TXE_BIT)
+
 // Transmission complete
 #define USART_SR_TC_BIT 6
 #define USART_SR_TC_COMPLETED (1 << USART_SR_TC_BIT)
 
+
+// Read data register not empty
+#define USART_SR_RXNE_BIT 5
+#define USART_SR_RXNE_READY (1 <<USART_SR_RXNE_BIT)
+
 // CR Register
+// Oversampling mode
+#define USART_CR1_OVER8_BIT 15
+#define USART_CR1_OVER8_8 (1 << USART_CR1_OVER8_BIT)
+
 // USART enable
 #define USART_CR1_UE_BIT 13
 #define USART_CR1_UE_ENABLE (1 << USART_CR1_UE_BIT)

todo.txt

@@ -0,0 +1,2 @@
+- implement UART
+- implement tim4 interrupt