Add gpio.{h, c}

Makefile

@@ -8,6 +8,8 @@ CFLAGS += -ffunction-sections -fdata-sections
 CFLAGS += -fno-builtin
 # "-fno-common ... specifies that the compiler places uninitialized global variables in the BSS section of the object file."
 CFLAGS += -fno-common
+# Use experimental binary literal gcc extension (to be able to use binary literals; e.g. 0b0101)
+CFLAGS += -std=c2x
 
 DEBUG ?= 1
 ifeq ($(DEBUG), 0)

build/final.elf.map

@@ -1,6 +1,56 @@
 
 Discarded input sections
 
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .group         0x00000000        0xc build/gpio.o
+ .text          0x00000000        0x0 build/gpio.o
+ .data          0x00000000        0x0 build/gpio.o
+ .bss           0x00000000        0x0 build/gpio.o
+ .text.gpio_set_mode
+                0x00000000       0x62 build/gpio.o
+ .text.gpio_write
+                0x00000000       0x4c build/gpio.o
+ .debug_info    0x00000000      0x21a build/gpio.o
+ .debug_abbrev  0x00000000      0x12b build/gpio.o
+ .debug_aranges
+                0x00000000       0x28 build/gpio.o
+ .debug_rnglists
+                0x00000000       0x19 build/gpio.o
+ .debug_macro   0x00000000      0xb56 build/gpio.o
+ .debug_macro   0x00000000       0x22 build/gpio.o
+ .debug_macro   0x00000000       0x75 build/gpio.o
+ .debug_macro   0x00000000       0x2a build/gpio.o
+ .debug_macro   0x00000000       0x5c build/gpio.o
+ .debug_macro   0x00000000       0x3c build/gpio.o
+ .debug_macro   0x00000000      0x103 build/gpio.o
+ .debug_macro   0x00000000       0x3a build/gpio.o
+ .debug_macro   0x00000000       0x57 build/gpio.o
+ .debug_macro   0x00000000       0x6a build/gpio.o
+ .debug_macro   0x00000000      0x1df build/gpio.o
+ .debug_macro   0x00000000       0x89 build/gpio.o
+ .debug_macro   0x00000000      0x4cc build/gpio.o
+ .debug_macro   0x00000000       0x22 build/gpio.o
+ .debug_macro   0x00000000       0x34 build/gpio.o
+ .debug_line    0x00000000      0x116 build/gpio.o
+ .debug_str     0x00000000     0x551a build/gpio.o
+ .comment       0x00000000       0x46 build/gpio.o
+ .debug_line_str
+                0x00000000      0x260 build/gpio.o
+ .debug_frame   0x00000000       0x60 build/gpio.o
+ .ARM.attributes
+                0x00000000       0x34 build/gpio.o
  .text          0x00000000        0x0 build/main.o
  .data          0x00000000        0x0 build/main.o
  .bss           0x00000000        0x0 build/main.o
@@ -13,6 +63,10 @@ Discarded input sections
  .text          0x00000000        0x0 build/startup.o
  .data          0x00000000        0x0 build/startup.o
  .bss           0x00000000        0x0 build/startup.o
+ .debug_macro   0x00000000       0x22 build/startup.o
+ .debug_macro   0x00000000      0x103 build/startup.o
+ .debug_macro   0x00000000       0x6a build/startup.o
+ .debug_macro   0x00000000      0x1df build/startup.o
 
 Memory Configuration
 
@@ -25,6 +79,7 @@ Linker script and memory map
 
 LOAD /nix/store/yr89i11mszv2az19r26l372zgaiivj1c-gcc-arm-embedded-12.3.rel1/bin/../lib/gcc/arm-none-eabi/12.3.1/../../../../arm-none-eabi/lib/libc_nano.a
 LOAD /nix/store/yr89i11mszv2az19r26l372zgaiivj1c-gcc-arm-embedded-12.3.rel1/bin/../lib/gcc/arm-none-eabi/12.3.1/libgcc.a
+LOAD build/gpio.o
 LOAD build/main.o
 LOAD build/startup.o
                 0x20020000                        stack_start = (ORIGIN (sram) + LENGTH (sram))
@@ -182,24 +237,20 @@ LOAD linker stubs
  .debug_rnglists
                 0x00000013       0x1f build/startup.o
 
-.debug_macro    0x00000000     0x19f9
+.debug_macro    0x00000000     0x165f
- .debug_macro   0x00000000      0xab0 build/main.o
+ .debug_macro   0x00000000      0xab6 build/main.o
- .debug_macro   0x00000ab0      0xafc build/startup.o
+ .debug_macro   0x00000ab6      0xb02 build/startup.o
- .debug_macro   0x000015ac       0x22 build/startup.o
+ .debug_macro   0x000015b8       0x56 build/startup.o
- .debug_macro   0x000015ce       0x8e build/startup.o
+ .debug_macro   0x0000160e       0x51 build/startup.o
- .debug_macro   0x0000165c       0x51 build/startup.o
- .debug_macro   0x000016ad      0x103 build/startup.o
- .debug_macro   0x000017b0       0x6a build/startup.o
- .debug_macro   0x0000181a      0x1df build/startup.o
 
 .debug_line     0x00000000      0x139
  .debug_line    0x00000000       0x4f build/main.o
  .debug_line    0x0000004f       0xea build/startup.o
 
-.debug_str      0x00000000     0x3c00
+.debug_str      0x00000000     0x3b8e
- .debug_str     0x00000000     0x2db0 build/main.o
+ .debug_str     0x00000000     0x2dcb build/main.o
- .debug_str     0x00002db0      0xe50 build/startup.o
+ .debug_str     0x00002dcb      0xdc3 build/startup.o
-                               0x3d51 (size before relaxing)
+                               0x3cdf (size before relaxing)
 
 .comment        0x00000000       0x45
  .comment       0x00000000       0x45 build/main.o

build/main.S

@@ -60,16 +60,16 @@ main:
 	.byte	0x4
 	.4byte	.Ldebug_abbrev0
 	.uleb128 0x1
-	.4byte	.LASF454
-	.byte	0x1d
 	.4byte	.LASF455
+	.byte	0x1d
 	.4byte	.LASF456
+	.4byte	.LASF457
 	.4byte	.LLRL0
 	.4byte	0
 	.4byte	.Ldebug_line0
 	.4byte	.Ldebug_macro0
 	.uleb128 0x2
-	.4byte	.LASF457
+	.4byte	.LASF458
 	.byte	0x1
 	.byte	0x3
 	.byte	0x5
@@ -1355,14 +1355,14 @@ main:
 	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF391
-	.byte	0x6
-	.uleb128 0
-	.4byte	.LASF392
 	.byte	0x5
 	.uleb128 0
-	.4byte	.LASF393
+	.4byte	.LASF392
 	.byte	0x6
 	.uleb128 0
+	.4byte	.LASF393
+	.byte	0x5
+	.uleb128 0
 	.4byte	.LASF394
 	.byte	0x6
 	.uleb128 0
@@ -1373,10 +1373,10 @@ main:
 	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF397
-	.byte	0x5
+	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF398
-	.byte	0x6
+	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF399
 	.byte	0x6
@@ -1385,16 +1385,16 @@ main:
 	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF401
-	.byte	0x5
+	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF402
 	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF403
-	.byte	0x6
+	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF404
-	.byte	0x5
+	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF405
 	.byte	0x5
@@ -1403,19 +1403,19 @@ main:
 	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF407
-	.byte	0x6
+	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF408
-	.byte	0x5
+	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF409
 	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF410
-	.byte	0x6
+	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF411
-	.byte	0x5
+	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF412
 	.byte	0x5
@@ -1433,10 +1433,10 @@ main:
 	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF417
-	.byte	0x6
+	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF418
-	.byte	0x5
+	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF419
 	.byte	0x5
@@ -1445,14 +1445,14 @@ main:
 	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF421
-	.byte	0x6
-	.uleb128 0
-	.4byte	.LASF422
 	.byte	0x5
 	.uleb128 0
-	.4byte	.LASF423
+	.4byte	.LASF422
 	.byte	0x6
 	.uleb128 0
+	.4byte	.LASF423
+	.byte	0x5
+	.uleb128 0
 	.4byte	.LASF424
 	.byte	0x6
 	.uleb128 0
@@ -1469,10 +1469,10 @@ main:
 	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF429
-	.byte	0x5
+	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF430
-	.byte	0x6
+	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF431
 	.byte	0x6
@@ -1481,7 +1481,7 @@ main:
 	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF433
-	.byte	0x5
+	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF434
 	.byte	0x5
@@ -1493,10 +1493,10 @@ main:
 	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF437
-	.byte	0x6
+	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF438
-	.byte	0x5
+	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF439
 	.byte	0x5
@@ -1505,14 +1505,14 @@ main:
 	.byte	0x5
 	.uleb128 0
 	.4byte	.LASF441
-	.byte	0x6
-	.uleb128 0
-	.4byte	.LASF442
 	.byte	0x5
 	.uleb128 0
-	.4byte	.LASF443
+	.4byte	.LASF442
 	.byte	0x6
 	.uleb128 0
+	.4byte	.LASF443
+	.byte	0x5
+	.uleb128 0
 	.4byte	.LASF444
 	.byte	0x6
 	.uleb128 0
@@ -1529,7 +1529,7 @@ main:
 	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF449
-	.byte	0x5
+	.byte	0x6
 	.uleb128 0
 	.4byte	.LASF450
 	.byte	0x5
@@ -1539,17 +1539,20 @@ main:
 	.uleb128 0
 	.4byte	.LASF452
 	.byte	0x5
-	.uleb128 0x1
+	.uleb128 0
 	.4byte	.LASF453
+	.byte	0x5
+	.uleb128 0x1
+	.4byte	.LASF454
 	.byte	0x4
 	.byte	0
 	.section	.debug_line,"",%progbits
 .Ldebug_line0:
 	.section	.debug_str,"MS",%progbits,1
-.LASF428:
+.LASF429:
 	.ascii	"__ARM_FEATURE_FP16_VECTOR_ARITHMETIC\000"
-.LASF95:
+.LASF1:
-	.ascii	"__SIG_ATOMIC_MAX__ 0x7fffffff\000"
+	.ascii	"__STDC_VERSION__ 202000L\000"
 .LASF352:
 	.ascii	"__TA_FBIT__ 63\000"
 .LASF262:
@@ -1560,13 +1563,13 @@ main:
 	.ascii	"__UINT_FAST8_TYPE__ unsigned int\000"
 .LASF218:
 	.ascii	"__FLT64_MAX_EXP__ 1024\000"
-.LASF416:
+.LASF417:
 	.ascii	"__thumb2__ 1\000"
 .LASF234:
 	.ascii	"__FLT32X_MAX_EXP__ 1024\000"
 .LASF129:
 	.ascii	"__INT_FAST16_WIDTH__ 32\000"
-.LASF379:
+.LASF380:
 	.ascii	"__GCC_ATOMIC_TEST_AND_SET_TRUEVAL 1\000"
 .LASF315:
 	.ascii	"__ULACCUM_EPSILON__ 0x1P-32ULK\000"
@@ -1576,9 +1579,9 @@ main:
 	.ascii	"__USQ_IBIT__ 0\000"
 .LASF119:
 	.ascii	"__UINT8_C(c) c\000"
-.LASF431:
+.LASF432:
 	.ascii	"__ARM_NEON__\000"
-.LASF387:
+.LASF388:
 	.ascii	"__SIZEOF_WINT_T__ 4\000"
 .LASF327:
 	.ascii	"__QQ_IBIT__ 0\000"
@@ -1590,15 +1593,15 @@ main:
 	.ascii	"__DBL_MIN_EXP__ (-1021)\000"
 .LASF85:
 	.ascii	"__LONG_LONG_WIDTH__ 64\000"
-.LASF372:
+.LASF373:
 	.ascii	"__GCC_ATOMIC_CHAR16_T_LOCK_FREE 2\000"
-.LASF445:
+.LASF446:
 	.ascii	"__ARM_FEATURE_CDE_COPROC\000"
-.LASF407:
+.LASF408:
 	.ascii	"__ARM_SIZEOF_WCHAR_T 4\000"
-.LASF424:
+.LASF425:
 	.ascii	"__ARM_FP16_FORMAT_IEEE\000"
-.LASF397:
+.LASF398:
 	.ascii	"__ARM_FEATURE_COMPLEX\000"
 .LASF277:
 	.ascii	"__LLFRACT_IBIT__ 0\000"
@@ -1608,9 +1611,9 @@ main:
 	.ascii	"__USFRACT_MIN__ 0.0UHR\000"
 .LASF6:
 	.ascii	"__GNUC_MINOR__ 3\000"
-.LASF441:
+.LASF442:
 	.ascii	"__ARM_ASM_SYNTAX_UNIFIED__ 1\000"
-.LASF392:
+.LASF393:
 	.ascii	"__ARM_FEATURE_CRYPTO\000"
 .LASF172:
 	.ascii	"__DBL_NORM_MAX__ ((double)1.7976931348623157e+308L)"
@@ -1629,9 +1632,9 @@ main:
 	.ascii	"__ORDER_BIG_ENDIAN__ 4321\000"
 .LASF284:
 	.ascii	"__ULLFRACT_MAX__ 0XFFFFFFFFFFFFFFFFP-64ULLR\000"
-.LASF381:
+.LASF382:
 	.ascii	"__GCC_CONSTRUCTIVE_SIZE 64\000"
-.LASF389:
+.LASF390:
 	.ascii	"__ARM_FEATURE_DSP 1\000"
 .LASF360:
 	.ascii	"__UTA_FBIT__ 64\000"
@@ -1647,11 +1650,11 @@ main:
 	.ascii	"__FLT_IS_IEC_60559__ 2\000"
 .LASF35:
 	.ascii	"__PTRDIFF_TYPE__ int\000"
-.LASF366:
+.LASF367:
 	.ascii	"__CHAR_UNSIGNED__ 1\000"
 .LASF44:
 	.ascii	"__INT16_TYPE__ short int\000"
-.LASF394:
+.LASF395:
 	.ascii	"__ARM_FEATURE_QRDMX\000"
 .LASF181:
 	.ascii	"__LDBL_DIG__ 15\000"
@@ -1677,7 +1680,7 @@ main:
 	.ascii	"__FLT32_MIN_10_EXP__ (-37)\000"
 .LASF267:
 	.ascii	"__LFRACT_IBIT__ 0\000"
-.LASF412:
+.LASF413:
 	.ascii	"__ARM_ARCH 7\000"
 .LASF3:
 	.ascii	"__STDC_UTF_32__ 1\000"
@@ -1687,7 +1690,7 @@ main:
 	.ascii	"__SCHAR_MAX__ 0x7f\000"
 .LASF222:
 	.ascii	"__FLT64_NORM_MAX__ 1.7976931348623157e+308F64\000"
-.LASF404:
+.LASF405:
 	.ascii	"__ARM_FEATURE_NUMERIC_MAXMIN\000"
 .LASF282:
 	.ascii	"__ULLFRACT_IBIT__ 0\000"
@@ -1695,7 +1698,7 @@ main:
 	.ascii	"__FLT64_DIG__ 15\000"
 .LASF9:
 	.ascii	"__ATOMIC_RELAXED 0\000"
-.LASF429:
+.LASF430:
 	.ascii	"__ARM_FEATURE_FP16_FML\000"
 .LASF80:
 	.ascii	"__SIZE_MAX__ 0xffffffffU\000"
@@ -1707,7 +1710,7 @@ main:
 	.ascii	"__ULLACCUM_MAX__ 0XFFFFFFFFFFFFFFFFP-32ULLK\000"
 .LASF313:
 	.ascii	"__ULACCUM_MIN__ 0.0ULK\000"
-.LASF423:
+.LASF424:
 	.ascii	"__ARM_FP 4\000"
 .LASF160:
 	.ascii	"__FLT_HAS_INFINITY__ 1\000"
@@ -1721,21 +1724,21 @@ main:
 	.ascii	"__INT8_C(c) c\000"
 .LASF212:
 	.ascii	"__FP_FAST_FMAF32 1\000"
-.LASF398:
+.LASF399:
 	.ascii	"__ARM_32BIT_STATE 1\000"
-.LASF438:
+.LASF439:
 	.ascii	"__FDPIC__\000"
 .LASF111:
 	.ascii	"__INT_LEAST16_WIDTH__ 16\000"
 .LASF323:
 	.ascii	"__ULLACCUM_MIN__ 0.0ULLK\000"
-.LASF396:
+.LASF397:
 	.ascii	"__ARM_FEATURE_DOTPROD\000"
-.LASF432:
+.LASF433:
 	.ascii	"__ARM_NEON\000"
-.LASF400:
+.LASF401:
 	.ascii	"__ARM_FEATURE_CMSE\000"
-.LASF456:
+.LASF457:
 	.ascii	"/home/alex/code/own/c-compile-experiments\000"
 .LASF229:
 	.ascii	"__FLT64_IS_IEC_60559__ 2\000"
@@ -1743,7 +1746,7 @@ main:
 	.ascii	"__FLT32_HAS_DENORM__ 1\000"
 .LASF225:
 	.ascii	"__FLT64_DENORM_MIN__ 4.9406564584124654e-324F64\000"
-.LASF367:
+.LASF368:
 	.ascii	"__GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1\000"
 .LASF349:
 	.ascii	"__SA_IBIT__ 16\000"
@@ -1757,14 +1760,19 @@ main:
 	.ascii	"__FLT_DIG__ 6\000"
 .LASF174:
 	.ascii	"__DBL_EPSILON__ ((double)2.2204460492503131e-16L)\000"
-.LASF368:
+.LASF369:
 	.ascii	"__GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 1\000"
 .LASF350:
 	.ascii	"__DA_FBIT__ 31\000"
-.LASF406:
+.LASF407:
 	.ascii	"__ARM_SIZEOF_MINIMAL_ENUM 1\000"
-.LASF452:
+.LASF453:
 	.ascii	"__USES_INITFINI__ 1\000"
+.LASF455:
+	.ascii	"GNU C2X 12.3.1 20230626 -mcpu=cortex-m4 -mthumb -mf"
+	.ascii	"loat-abi=hard -mfpu=fpv4-sp-d16 -march=armv7e-m+fp "
+	.ascii	"-g3 -ggdb -O0 -std=c2x -ffunction-sections -fdata-s"
+	.ascii	"ections -fno-builtin -fno-common\000"
 .LASF141:
 	.ascii	"__GCC_IEC_559 0\000"
 .LASF295:
@@ -1781,7 +1789,7 @@ main:
 	.ascii	"__SFRACT_MAX__ 0X7FP-7HR\000"
 .LASF5:
 	.ascii	"__GNUC__ 12\000"
-.LASF437:
+.LASF438:
 	.ascii	"__ARM_EABI__ 1\000"
 .LASF118:
 	.ascii	"__UINT_LEAST8_MAX__ 0xff\000"
@@ -1815,7 +1823,7 @@ main:
 	.ascii	"__FLT64_HAS_INFINITY__ 1\000"
 .LASF241:
 	.ascii	"__FLT32X_DENORM_MIN__ 4.9406564584124654e-324F32x\000"
-.LASF427:
+.LASF428:
 	.ascii	"__ARM_FEATURE_FP16_SCALAR_ARITHMETIC\000"
 .LASF286:
 	.ascii	"__SACCUM_FBIT__ 7\000"
@@ -1827,7 +1835,7 @@ main:
 	.ascii	"__FLT64_MIN__ 2.2250738585072014e-308F64\000"
 .LASF258:
 	.ascii	"__FRACT_MIN__ (-0.5R-0.5R)\000"
-.LASF376:
+.LASF377:
 	.ascii	"__GCC_ATOMIC_INT_LOCK_FREE 2\000"
 .LASF90:
 	.ascii	"__INTMAX_MAX__ 0x7fffffffffffffffLL\000"
@@ -1841,15 +1849,15 @@ main:
 	.ascii	"__FLT64_MAX_10_EXP__ 308\000"
 .LASF287:
 	.ascii	"__SACCUM_IBIT__ 8\000"
-.LASF388:
+.LASF389:
 	.ascii	"__SIZEOF_PTRDIFF_T__ 4\000"
 .LASF248:
 	.ascii	"__SFRACT_MIN__ (-0.5HR-0.5HR)\000"
 .LASF357:
 	.ascii	"__USA_IBIT__ 16\000"
-.LASF439:
+.LASF440:
 	.ascii	"__ARM_ARCH_EXT_IDIV__ 1\000"
-.LASF393:
+.LASF394:
 	.ascii	"__ARM_FEATURE_UNALIGNED 1\000"
 .LASF294:
 	.ascii	"__USACCUM_MAX__ 0XFFFFP-8UHK\000"
@@ -1857,7 +1865,7 @@ main:
 	.ascii	"__UINT32_C(c) c ## UL\000"
 .LASF358:
 	.ascii	"__UDA_FBIT__ 32\000"
-.LASF417:
+.LASF418:
 	.ascii	"__THUMBEL__ 1\000"
 .LASF25:
 	.ascii	"__BIGGEST_ALIGNMENT__ 8\000"
@@ -1869,7 +1877,7 @@ main:
 	.ascii	"__UINT_FAST8_MAX__ 0xffffffffU\000"
 .LASF26:
 	.ascii	"__ORDER_LITTLE_ENDIAN__ 1234\000"
-.LASF383:
+.LASF384:
 	.ascii	"__HAVE_SPECULATION_SAFE_VALUE 1\000"
 .LASF318:
 	.ascii	"__LLACCUM_MIN__ (-0X1P31LLK-0X1P31LLK)\000"
@@ -1887,13 +1895,13 @@ main:
 	.ascii	"__UINT16_TYPE__ short unsigned int\000"
 .LASF86:
 	.ascii	"__WCHAR_WIDTH__ 32\000"
-.LASF371:
+.LASF372:
 	.ascii	"__GCC_ATOMIC_CHAR_LOCK_FREE 2\000"
 .LASF339:
 	.ascii	"__UHQ_IBIT__ 0\000"
 .LASF261:
 	.ascii	"__UFRACT_FBIT__ 16\000"
-.LASF403:
+.LASF404:
 	.ascii	"__ARM_FEATURE_CLZ 1\000"
 .LASF74:
 	.ascii	"__LONG_LONG_MAX__ 0x7fffffffffffffffLL\000"
@@ -1909,17 +1917,17 @@ main:
 	.ascii	"__FLT32X_MANT_DIG__ 53\000"
 .LASF365:
 	.ascii	"__NO_INLINE__ 1\000"
-.LASF442:
+.LASF443:
 	.ascii	"__ARM_FEATURE_COPROC\000"
 .LASF273:
 	.ascii	"__ULFRACT_MIN__ 0.0ULR\000"
 .LASF147:
 	.ascii	"__FLT_MANT_DIG__ 24\000"
-.LASF411:
+.LASF412:
 	.ascii	"__ARM_ARCH\000"
 .LASF220:
 	.ascii	"__FLT64_DECIMAL_DIG__ 17\000"
-.LASF369:
+.LASF370:
 	.ascii	"__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1\000"
 .LASF199:
 	.ascii	"__FLT32_MIN_EXP__ (-125)\000"
@@ -1935,7 +1943,7 @@ main:
 	.ascii	"__DBL_MIN_10_EXP__ (-307)\000"
 .LASF292:
 	.ascii	"__USACCUM_IBIT__ 8\000"
-.LASF434:
+.LASF435:
 	.ascii	"__THUMB_INTERWORK__ 1\000"
 .LASF198:
 	.ascii	"__FLT32_DIG__ 6\000"
@@ -1949,13 +1957,13 @@ main:
 	.ascii	"__INT_LEAST64_MAX__ 0x7fffffffffffffffLL\000"
 .LASF296:
 	.ascii	"__ACCUM_FBIT__ 15\000"
-.LASF374:
+.LASF375:
 	.ascii	"__GCC_ATOMIC_WCHAR_T_LOCK_FREE 2\000"
 .LASF312:
 	.ascii	"__ULACCUM_IBIT__ 32\000"
 .LASF276:
 	.ascii	"__LLFRACT_FBIT__ 63\000"
-.LASF378:
+.LASF379:
 	.ascii	"__GCC_ATOMIC_LLONG_LOCK_FREE 1\000"
 .LASF108:
 	.ascii	"__INT_LEAST8_WIDTH__ 8\000"
@@ -1969,7 +1977,7 @@ main:
 	.ascii	"__UACCUM_FBIT__ 16\000"
 .LASF94:
 	.ascii	"__INTMAX_WIDTH__ 64\000"
-.LASF444:
+.LASF445:
 	.ascii	"__ARM_FEATURE_CDE\000"
 .LASF266:
 	.ascii	"__LFRACT_FBIT__ 31\000"
@@ -1983,9 +1991,9 @@ main:
 	.ascii	"__GNUC_STDC_INLINE__ 1\000"
 .LASF165:
 	.ascii	"__DBL_DIG__ 15\000"
-.LASF420:
+.LASF421:
 	.ascii	"__ARMEL__ 1\000"
-.LASF418:
+.LASF419:
 	.ascii	"__ARM_ARCH_ISA_THUMB\000"
 .LASF306:
 	.ascii	"__LACCUM_FBIT__ 31\000"
@@ -1993,7 +2001,7 @@ main:
 	.ascii	"__UTQ_IBIT__ 0\000"
 .LASF156:
 	.ascii	"__FLT_MIN__ 1.1754943508222875e-38F\000"
-.LASF377:
+.LASF378:
 	.ascii	"__GCC_ATOMIC_LONG_LOCK_FREE 2\000"
 .LASF231:
 	.ascii	"__FLT32X_DIG__ 15\000"
@@ -2003,9 +2011,7 @@ main:
 	.ascii	"__UDQ_FBIT__ 64\000"
 .LASF128:
 	.ascii	"__INT_FAST16_MAX__ 0x7fffffff\000"
-.LASF347:
+.LASF420:
-	.ascii	"__HA_IBIT__ 8\000"
-.LASF419:
 	.ascii	"__ARM_ARCH_ISA_THUMB 2\000"
 .LASF344:
 	.ascii	"__UTQ_FBIT__ 128\000"
@@ -2015,7 +2021,7 @@ main:
 	.ascii	"__FLT32X_IS_IEC_60559__ 2\000"
 .LASF139:
 	.ascii	"__INTPTR_WIDTH__ 32\000"
-.LASF370:
+.LASF371:
 	.ascii	"__GCC_ATOMIC_BOOL_LOCK_FREE 2\000"
 .LASF188:
 	.ascii	"__LDBL_MAX__ 1.7976931348623157e+308L\000"
@@ -2023,7 +2029,7 @@ main:
 	.ascii	"__FINITE_MATH_ONLY__ 0\000"
 .LASF289:
 	.ascii	"__SACCUM_MAX__ 0X7FFFP-7HK\000"
-.LASF410:
+.LASF411:
 	.ascii	"__arm__ 1\000"
 .LASF180:
 	.ascii	"__LDBL_MANT_DIG__ 53\000"
@@ -2031,15 +2037,15 @@ main:
 	.ascii	"__TQ_IBIT__ 0\000"
 .LASF354:
 	.ascii	"__UHA_FBIT__ 8\000"
-.LASF414:
+.LASF415:
 	.ascii	"__GCC_ASM_FLAG_OUTPUTS__ 1\000"
-.LASF451:
+.LASF452:
 	.ascii	"__ELF__ 1\000"
-.LASF408:
+.LASF409:
 	.ascii	"__ARM_ARCH_PROFILE\000"
 .LASF110:
 	.ascii	"__INT16_C(c) c\000"
-.LASF384:
+.LASF385:
 	.ascii	"__GCC_HAVE_DWARF2_CFI_ASM 1\000"
 .LASF105:
 	.ascii	"__UINT64_MAX__ 0xffffffffffffffffULL\000"
@@ -2051,7 +2057,7 @@ main:
 	.ascii	"__USFRACT_EPSILON__ 0x1P-8UHR\000"
 .LASF11:
 	.ascii	"__ATOMIC_ACQUIRE 2\000"
-.LASF443:
+.LASF444:
 	.ascii	"__ARM_FEATURE_COPROC 15\000"
 .LASF0:
 	.ascii	"__STDC__ 1\000"
@@ -2063,7 +2069,7 @@ main:
 	.ascii	"__ATOMIC_CONSUME 1\000"
 .LASF131:
 	.ascii	"__INT_FAST32_WIDTH__ 32\000"
-.LASF449:
+.LASF450:
 	.ascii	"__ARM_BF16_FORMAT_ALTERNATIVE\000"
 .LASF37:
 	.ascii	"__WINT_TYPE__ unsigned int\000"
@@ -2081,7 +2087,7 @@ main:
 	.ascii	"__SIZEOF_DOUBLE__ 8\000"
 .LASF7:
 	.ascii	"__GNUC_PATCHLEVEL__ 1\000"
-.LASF450:
+.LASF451:
 	.ascii	"__GXX_TYPEINFO_EQUALITY_INLINE 0\000"
 .LASF259:
 	.ascii	"__FRACT_MAX__ 0X7FFFP-15R\000"
@@ -2093,7 +2099,7 @@ main:
 	.ascii	"__FLT_NORM_MAX__ 3.4028234663852886e+38F\000"
 .LASF263:
 	.ascii	"__UFRACT_MIN__ 0.0UR\000"
-.LASF433:
+.LASF434:
 	.ascii	"__ARM_NEON_FP\000"
 .LASF2:
 	.ascii	"__STDC_UTF_16__ 1\000"
@@ -2115,7 +2121,7 @@ main:
 	.ascii	"__LDBL_MIN_EXP__ (-1021)\000"
 .LASF281:
 	.ascii	"__ULLFRACT_FBIT__ 64\000"
-.LASF386:
+.LASF387:
 	.ascii	"__SIZEOF_WCHAR_T__ 4\000"
 .LASF30:
 	.ascii	"__FLOAT_WORD_ORDER__ __ORDER_LITTLE_ENDIAN__\000"
@@ -2123,7 +2129,7 @@ main:
 	.ascii	"__ACCUM_MAX__ 0X7FFFFFFFP-15K\000"
 .LASF89:
 	.ascii	"__SIZE_WIDTH__ 32\000"
-.LASF391:
+.LASF392:
 	.ascii	"__ARM_FEATURE_SAT 1\000"
 .LASF96:
 	.ascii	"__SIG_ATOMIC_MIN__ (-__SIG_ATOMIC_MAX__ - 1)\000"
@@ -2149,15 +2155,15 @@ main:
 	.ascii	"__DQ_FBIT__ 63\000"
 .LASF355:
 	.ascii	"__UHA_IBIT__ 8\000"
-.LASF402:
+.LASF403:
 	.ascii	"__ARM_FEATURE_LDREX 7\000"
 .LASF97:
 	.ascii	"__SIG_ATOMIC_WIDTH__ 32\000"
-.LASF448:
+.LASF449:
 	.ascii	"__ARM_FEATURE_BF16_VECTOR_ARITHMETIC\000"
 .LASF71:
 	.ascii	"__SHRT_MAX__ 0x7fff\000"
-.LASF426:
+.LASF427:
 	.ascii	"__ARM_FP16_ARGS\000"
 .LASF28:
 	.ascii	"__ORDER_PDP_ENDIAN__ 3412\000"
@@ -2175,6 +2181,8 @@ main:
 	.ascii	"__UQQ_FBIT__ 8\000"
 .LASF265:
 	.ascii	"__UFRACT_EPSILON__ 0x1P-16UR\000"
+.LASF95:
+	.ascii	"__SIG_ATOMIC_MAX__ 0x7fffffff\000"
 .LASF69:
 	.ascii	"__GXX_ABI_VERSION 1017\000"
 .LASF117:
@@ -2183,11 +2191,11 @@ main:
 	.ascii	"__INT32_TYPE__ long int\000"
 .LASF233:
 	.ascii	"__FLT32X_MIN_10_EXP__ (-307)\000"
-.LASF447:
+.LASF448:
 	.ascii	"__ARM_FEATURE_BF16_SCALAR_ARITHMETIC\000"
 .LASF65:
 	.ascii	"__UINT_FAST32_TYPE__ unsigned int\000"
-.LASF440:
+.LASF441:
 	.ascii	"__ARM_FEATURE_IDIV 1\000"
 .LASF184:
 	.ascii	"__LDBL_MAX_EXP__ 1024\000"
@@ -2201,9 +2209,9 @@ main:
 	.ascii	"__FLT64_MAX__ 1.7976931348623157e+308F64\000"
 .LASF122:
 	.ascii	"__UINT_LEAST32_MAX__ 0xffffffffUL\000"
-.LASF380:
+.LASF381:
 	.ascii	"__GCC_DESTRUCTIVE_SIZE 64\000"
-.LASF415:
+.LASF416:
 	.ascii	"__thumb__ 1\000"
 .LASF195:
 	.ascii	"__LDBL_HAS_QUIET_NAN__ 1\000"
@@ -2227,7 +2235,7 @@ main:
 	.ascii	"__INT64_C(c) c ## LL\000"
 .LASF328:
 	.ascii	"__HQ_FBIT__ 15\000"
-.LASF405:
+.LASF406:
 	.ascii	"__ARM_FEATURE_SIMD32 1\000"
 .LASF75:
 	.ascii	"__WCHAR_MAX__ 0xffffffffU\000"
@@ -2237,7 +2245,7 @@ main:
 	.ascii	"__UINT8_TYPE__ unsigned char\000"
 .LASF82:
 	.ascii	"__SHRT_WIDTH__ 16\000"
-.LASF422:
+.LASF423:
 	.ascii	"__ARM_FP\000"
 .LASF51:
 	.ascii	"__INT_LEAST8_TYPE__ signed char\000"
@@ -2253,7 +2261,7 @@ main:
 	.ascii	"__SIZEOF_POINTER__ 4\000"
 .LASF304:
 	.ascii	"__UACCUM_MAX__ 0XFFFFFFFFP-16UK\000"
-.LASF421:
+.LASF422:
 	.ascii	"__VFP_FP__ 1\000"
 .LASF274:
 	.ascii	"__ULFRACT_MAX__ 0XFFFFFFFFP-32ULR\000"
@@ -2267,13 +2275,13 @@ main:
 	.ascii	"__SACCUM_MIN__ (-0X1P7HK-0X1P7HK)\000"
 .LASF83:
 	.ascii	"__INT_WIDTH__ 32\000"
-.LASF382:
+.LASF383:
 	.ascii	"__GCC_ATOMIC_POINTER_LOCK_FREE 2\000"
 .LASF125:
 	.ascii	"__UINT64_C(c) c ## ULL\000"
 .LASF310:
 	.ascii	"__LACCUM_EPSILON__ 0x1P-31LK\000"
-.LASF457:
+.LASF458:
 	.ascii	"main\000"
 .LASF250:
 	.ascii	"__SFRACT_EPSILON__ 0x1P-7HR\000"
@@ -2283,9 +2291,9 @@ main:
 	.ascii	"__FLT32X_MAX__ 1.7976931348623157e+308F32x\000"
 .LASF340:
 	.ascii	"__USQ_FBIT__ 32\000"
-.LASF1:
+.LASF347:
-	.ascii	"__STDC_VERSION__ 201710L\000"
+	.ascii	"__HA_IBIT__ 8\000"
-.LASF373:
+.LASF374:
 	.ascii	"__GCC_ATOMIC_CHAR32_T_LOCK_FREE 2\000"
 .LASF260:
 	.ascii	"__FRACT_EPSILON__ 0x1P-15R\000"
@@ -2293,9 +2301,9 @@ main:
 	.ascii	"__STDC_HOSTED__ 1\000"
 .LASF138:
 	.ascii	"__INTPTR_MAX__ 0x7fffffff\000"
-.LASF385:
+.LASF386:
 	.ascii	"__PRAGMA_REDEFINE_EXTNAME 1\000"
-.LASF453:
+.LASF454:
 	.ascii	"exit 42\000"
 .LASF224:
 	.ascii	"__FLT64_EPSILON__ 2.2204460492503131e-16F64\000"
@@ -2315,7 +2323,7 @@ main:
 	.ascii	"__LDBL_EPSILON__ 2.2204460492503131e-16L\000"
 .LASF67:
 	.ascii	"__INTPTR_TYPE__ int\000"
-.LASF436:
+.LASF437:
 	.ascii	"__ARM_PCS_VFP 1\000"
 .LASF145:
 	.ascii	"__DEC_EVAL_METHOD__ 2\000"
@@ -2339,16 +2347,11 @@ main:
 	.ascii	"__SIZE_TYPE__ unsigned int\000"
 .LASF321:
 	.ascii	"__ULLACCUM_FBIT__ 32\000"
-.LASF454:
-	.ascii	"GNU C17 12.3.1 20230626 -mcpu=cortex-m4 -mthumb -mf"
-	.ascii	"loat-abi=hard -mfpu=fpv4-sp-d16 -march=armv7e-m+fp "
-	.ascii	"-g3 -ggdb -O0 -ffunction-sections -fdata-sections -"
-	.ascii	"fno-builtin -fno-common\000"
 .LASF216:
 	.ascii	"__FLT64_MIN_EXP__ (-1021)\000"
 .LASF256:
 	.ascii	"__FRACT_FBIT__ 15\000"
-.LASF375:
+.LASF376:
 	.ascii	"__GCC_ATOMIC_SHORT_LOCK_FREE 2\000"
 .LASF361:
 	.ascii	"__UTA_IBIT__ 64\000"
@@ -2362,7 +2365,7 @@ main:
 	.ascii	"__FLT_EVAL_METHOD_TS_18661_3__ 0\000"
 .LASF177:
 	.ascii	"__DBL_HAS_INFINITY__ 1\000"
-.LASF390:
+.LASF391:
 	.ascii	"__ARM_FEATURE_QBIT 1\000"
 .LASF61:
 	.ascii	"__INT_FAST32_TYPE__ int\000"
@@ -2374,16 +2377,16 @@ main:
 	.ascii	"__INTMAX_TYPE__ long long int\000"
 .LASF91:
 	.ascii	"__INTMAX_C(c) c ## LL\000"
-.LASF399:
+.LASF400:
 	.ascii	"__ARM_FEATURE_MVE\000"
-.LASF413:
+.LASF414:
 	.ascii	"__APCS_32__ 1\000"
 .LASF175:
 	.ascii	"__DBL_DENORM_MIN__ ((double)4.9406564584124654e-324"
 	.ascii	"L)\000"
 .LASF50:
 	.ascii	"__UINT64_TYPE__ long long unsigned int\000"
-.LASF455:
+.LASF456:
 	.ascii	"src/main.c\000"
 .LASF244:
 	.ascii	"__FLT32X_HAS_QUIET_NAN__ 1\000"
@@ -2399,7 +2402,7 @@ main:
 	.ascii	"__FLT32X_HAS_INFINITY__ 1\000"
 .LASF56:
 	.ascii	"__UINT_LEAST16_TYPE__ short unsigned int\000"
-.LASF409:
+.LASF410:
 	.ascii	"__ARM_ARCH_PROFILE 77\000"
 .LASF127:
 	.ascii	"__INT_FAST8_WIDTH__ 32\000"
@@ -2407,13 +2410,15 @@ main:
 	.ascii	"__VERSION__ \"12.3.1 20230626\"\000"
 .LASF149:
 	.ascii	"__FLT_MIN_EXP__ (-125)\000"
-.LASF446:
+.LASF447:
 	.ascii	"__ARM_FEATURE_MATMUL_INT8\000"
 .LASF186:
 	.ascii	"__DECIMAL_DIG__ 17\000"
 .LASF113:
 	.ascii	"__INT32_C(c) c ## L\000"
-.LASF425:
+.LASF366:
+	.ascii	"__STRICT_ANSI__ 1\000"
+.LASF426:
 	.ascii	"__ARM_FP16_FORMAT_ALTERNATIVE\000"
 .LASF185:
 	.ascii	"__LDBL_MAX_10_EXP__ 308\000"
@@ -2425,7 +2430,7 @@ main:
 	.ascii	"__DBL_HAS_DENORM__ 1\000"
 .LASF32:
 	.ascii	"__GNUC_EXECUTION_CHARSET_NAME \"UTF-8\"\000"
-.LASF395:
+.LASF396:
 	.ascii	"__ARM_FEATURE_CRC32\000"
 .LASF202:
 	.ascii	"__FLT32_MAX_10_EXP__ 38\000"
@@ -2433,7 +2438,7 @@ main:
 	.ascii	"__QQ_FBIT__ 7\000"
 .LASF269:
 	.ascii	"__LFRACT_MAX__ 0X7FFFFFFFP-31LR\000"
-.LASF435:
+.LASF436:
 	.ascii	"__ARM_ARCH_7EM__ 1\000"
 .LASF112:
 	.ascii	"__INT_LEAST32_MAX__ 0x7fffffffL\000"
@@ -2445,7 +2450,7 @@ main:
 	.ascii	"__SIG_ATOMIC_TYPE__ int\000"
 .LASF278:
 	.ascii	"__LLFRACT_MIN__ (-0.5LLR-0.5LLR)\000"
-.LASF430:
+.LASF431:
 	.ascii	"__ARM_FEATURE_FMA 1\000"
 .LASF285:
 	.ascii	"__ULLFRACT_EPSILON__ 0x1P-64ULLR\000"
@@ -2453,7 +2458,7 @@ main:
 	.ascii	"__LDBL_HAS_DENORM__ 1\000"
 .LASF120:
 	.ascii	"__UINT_LEAST16_MAX__ 0xffff\000"
-.LASF401:
+.LASF402:
 	.ascii	"__ARM_FEATURE_LDREX\000"
 .LASF189:
 	.ascii	"__LDBL_NORM_MAX__ 1.7976931348623157e+308L\000"

build/main.i

@@ -3,7 +3,7 @@
 # 0 "<built-in>"
 #define __STDC__ 1
 # 0 "<built-in>"
-#define __STDC_VERSION__ 201710L
+#define __STDC_VERSION__ 202000L
 # 0 "<built-in>"
 #define __STDC_UTF_16__ 1
 # 0 "<built-in>"
@@ -733,6 +733,8 @@
 # 0 "<built-in>"
 #define __NO_INLINE__ 1
 # 0 "<built-in>"
+#define __STRICT_ANSI__ 1
+# 0 "<built-in>"
 #define __CHAR_UNSIGNED__ 1
 # 0 "<built-in>"
 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1

build/startup.i

@@ -3,7 +3,7 @@
 # 0 "<built-in>"
 #define __STDC__ 1
 # 0 "<built-in>"
-#define __STDC_VERSION__ 201710L
+#define __STDC_VERSION__ 202000L
 # 0 "<built-in>"
 #define __STDC_UTF_16__ 1
 # 0 "<built-in>"
@@ -733,6 +733,8 @@
 # 0 "<built-in>"
 #define __NO_INLINE__ 1
 # 0 "<built-in>"
+#define __STRICT_ANSI__ 1
+# 0 "<built-in>"
 #define __CHAR_UNSIGNED__ 1
 # 0 "<built-in>"
 #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_1 1
@@ -952,29 +954,14 @@
 
 
 #define __GNUC_PREREQ__(ma,mi) __GNUC_PREREQ(ma, mi)
-# 131 "/nix/store/yr89i11mszv2az19r26l372zgaiivj1c-gcc-arm-embedded-12.3.rel1/arm-none-eabi/include/sys/features.h" 3 4
+# 249 "/nix/store/yr89i11mszv2az19r26l372zgaiivj1c-gcc-arm-embedded-12.3.rel1/arm-none-eabi/include/sys/features.h" 3 4
-#undef _DEFAULT_SOURCE
+#define __ATFILE_VISIBLE 0
-#define _DEFAULT_SOURCE 1
-
-
-
-#undef _POSIX_SOURCE
-#define _POSIX_SOURCE 1
-#undef _POSIX_C_SOURCE
-#define _POSIX_C_SOURCE 200809L
-# 158 "/nix/store/yr89i11mszv2az19r26l372zgaiivj1c-gcc-arm-embedded-12.3.rel1/arm-none-eabi/include/sys/features.h" 3 4
-#undef _ATFILE_SOURCE
-#define _ATFILE_SOURCE 1
-# 247 "/nix/store/yr89i11mszv2az19r26l372zgaiivj1c-gcc-arm-embedded-12.3.rel1/arm-none-eabi/include/sys/features.h" 3 4
-#define __ATFILE_VISIBLE 1
 
 
 
 
 
-#define __BSD_VISIBLE 1
+#define __BSD_VISIBLE 0
-
-
 
 
 
@@ -991,15 +978,17 @@
 
 
 
-#define __MISC_VISIBLE 1
+
+
+#define __MISC_VISIBLE 0
+# 299 "/nix/store/yr89i11mszv2az19r26l372zgaiivj1c-gcc-arm-embedded-12.3.rel1/arm-none-eabi/include/sys/features.h" 3 4
+#define __POSIX_VISIBLE 0
 
 
 
 
 
-#define __POSIX_VISIBLE 200809
+#define __SVID_VISIBLE 0
-# 303 "/nix/store/yr89i11mszv2az19r26l372zgaiivj1c-gcc-arm-embedded-12.3.rel1/arm-none-eabi/include/sys/features.h" 3 4
-#define __SVID_VISIBLE 1
 # 319 "/nix/store/yr89i11mszv2az19r26l372zgaiivj1c-gcc-arm-embedded-12.3.rel1/arm-none-eabi/include/sys/features.h" 3 4
 #define __XSI_VISIBLE 0
 # 331 "/nix/store/yr89i11mszv2az19r26l372zgaiivj1c-gcc-arm-embedded-12.3.rel1/arm-none-eabi/include/sys/features.h" 3 4

src/gpio.c

@@ -0,0 +1,16 @@
+#include <inttypes.h>
+#include <stdbool.h>
+
+#include "gpio.h"
+
+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 &= ~(0x0011 << (pn * 2));       // Clear existing setting. Each pin uses 2 bits
+  gpio->MODER |= (mode & 0b011) << (pn * 2);  // Set new mode. Each pin uses 2 bits
+}
+
+void gpio_write(uint16_t pin, bool val) {
+  struct gpio *gpio = GPIO(PINPORT(pin));
+  gpio->BSRR = (0b0011 << PINNUM(pin)) << (val ? 0 : 16);
+}

src/gpio.h

@@ -0,0 +1,42 @@
+#ifndef GPIO_H_
+#define GPIO_H_
+
+#include <stdbool.h>
+#include <inttypes.h>
+
+struct gpio {
+  volatile uint32_t MODER;    // Port mode register
+  volatile uint32_t OTYPER;   // Port output type register
+  volatile uint32_t OSPEEDR;  // Port output speed register
+  volatile uint32_t PUPDR;    // Port pull-up/pull-down register
+  volatile uint32_t IDR;      // Port input data register
+  volatile uint32_t ODR;      // Port output data register
+  volatile uint32_t BSRR;     // Port bit set/reset register
+  volatile uint32_t LCKR;     // Port configuration lock register
+  volatile uint32_t AFRL[2];  // Alternative function low register
+  volatile uint32_t AFRH[2];  // Alternative function high register
+};
+
+#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)
+// Create a 16bit number from a port and pin
+#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
+#define PINPORT(pin) (pin >> 8)
+
+typedef enum {
+  GPIO_MODE_INPUT,
+  GPIO_MODE_OUTPUT,
+  GPIO_MODE_AF,
+  GPIO_MODE_ANALOG
+} GPIO_MODE;
+
+void gpio_set_mode(uint16_t pin, GPIO_MODE mode);
+void gpio_write(uint16_t pin, bool val);
+
+#endif