diff --git a/build/final.elf b/build/final.elf
index 72a7ae9..8cba364 100755
Binary files a/build/final.elf and b/build/final.elf differ
diff --git a/build/final.elf.map b/build/final.elf.map
index 64b9935..d9b7e68 100644
--- a/build/final.elf.map
+++ b/build/final.elf.map
@@ -327,15 +327,15 @@ LOAD linker stubs
  .debug_line    0x000002f0       0xea build/startup.o
  .debug_line    0x000003da       0xdf build/timer.o
 
-.debug_str      0x00000000     0x5eb8
- .debug_str     0x00000000     0x5372 build/gpio.o
-                               0x551a (size before relaxing)
- .debug_str     0x00005372      0xab2 build/main.o
-                               0x5f7c (size before relaxing)
- .debug_str     0x00005e24       0x88 build/startup.o
-                               0x3cdf (size before relaxing)
- .debug_str     0x00005eac        0xc build/timer.o
-                               0x5b1a (size before relaxing)
+.debug_str      0x00000000     0x5eb4
+ .debug_str     0x00000000     0x536f build/gpio.o
+                               0x5517 (size before relaxing)
+ .debug_str     0x0000536f      0xab1 build/main.o
+                               0x5f78 (size before relaxing)
+ .debug_str     0x00005e20       0x88 build/startup.o
+                               0x3cdc (size before relaxing)
+ .debug_str     0x00005ea8        0xc build/timer.o
+                               0x5b16 (size before relaxing)
 
 .comment        0x00000000       0x45
  .comment       0x00000000       0x45 build/gpio.o
@@ -356,19 +356,19 @@ LOAD linker stubs
                 0x0000009c       0x34 build/timer.o
 
 .debug_line_str
-                0x00000000      0x283
+                0x00000000      0x280
  .debug_line_str
-                0x00000000      0x24e build/gpio.o
-                                0x260 (size before relaxing)
+                0x00000000      0x24b build/gpio.o
+                                0x25d (size before relaxing)
  .debug_line_str
-                0x0000024e       0x23 build/main.o
-                                0x27c (size before relaxing)
+                0x0000024b       0x23 build/main.o
+                                0x279 (size before relaxing)
  .debug_line_str
-                0x00000271        0xa build/startup.o
-                                0x21b (size before relaxing)
+                0x0000026e        0xa build/startup.o
+                                0x218 (size before relaxing)
  .debug_line_str
-                0x0000027b        0x8 build/timer.o
-                                0x25e (size before relaxing)
+                0x00000278        0x8 build/timer.o
+                                0x25b (size before relaxing)
 
 .debug_frame    0x00000000      0x16c
  .debug_frame   0x00000000       0x60 build/gpio.o
diff --git a/build/gpio.S b/build/gpio.S
index e9c50e4..630dcd5 100644
--- a/build/gpio.S
+++ b/build/gpio.S
@@ -4361,8 +4361,6 @@ gpio_write:
 	.ascii	"__FLT_EVAL_METHOD_TS_18661_3__ 0\000"
 .LASF521:
 	.ascii	"int +2\000"
-.LASF896:
-	.ascii	"/home/alex/code/own/c-compile-experiments\000"
 .LASF636:
 	.ascii	"INT8_C(x) __INT8_C(x)\000"
 .LASF63:
@@ -5327,6 +5325,8 @@ gpio_write:
 	.ascii	"__SCN64LEAST(x) __LEAST64 __STRINGIFY(x)\000"
 .LASF280:
 	.ascii	"__LLFRACT_EPSILON__ 0x1P-63LLR\000"
+.LASF896:
+	.ascii	"/home/alex/code/own/stm32-falling-sand\000"
 .LASF249:
 	.ascii	"__SFRACT_MAX__ 0X7FP-7HR\000"
 .LASF230:
diff --git a/build/gpio.i b/build/gpio.i
index ba500f4..5d3f033 100644
--- a/build/gpio.i
+++ b/build/gpio.i
@@ -1,5 +1,5 @@
 # 0 "src/gpio.c"
-# 1 "/home/alex/code/own/c-compile-experiments//"
+# 1 "/home/alex/code/own/stm32-falling-sand//"
 # 0 "<built-in>"
 #define __STDC__ 1
 # 0 "<built-in>"
diff --git a/build/gpio.o b/build/gpio.o
index 81c99fc..64cd888 100644
Binary files a/build/gpio.o and b/build/gpio.o differ
diff --git a/build/main.S b/build/main.S
index 347c88a..4eb459c 100644
--- a/build/main.S
+++ b/build/main.S
@@ -4299,7 +4299,7 @@ main:
 	.uleb128 0x14
 	.4byte	.LASF929
 	.byte	0
-	.section	.debug_macro,"G",%progbits,wm4.timer.h.2.a5bec0ee8e2998a7b121820fb4e4e9a6,comdat
+	.section	.debug_macro,"G",%progbits,wm4.timer.h.2.2e929ede818fb0960868f1b0a08a1cbf,comdat
 .Ldebug_macro19:
 	.2byte	0x5
 	.byte	0
@@ -4322,8 +4322,6 @@ main:
 	.section	.debug_line,"",%progbits
 .Ldebug_line0:
 	.section	.debug_str,"MS",%progbits,1
-.LASF933:
-	.ascii	"TIM4_CR_CEN_BIT 0\000"
 .LASF734:
 	.ascii	"SCNxLEAST16 __SCN16LEAST(x)\000"
 .LASF635:
@@ -4479,8 +4477,6 @@ main:
 	.ascii	"PRIx8 __PRI8(x)\000"
 .LASF589:
 	.ascii	"INT8_MAX (__INT8_MAX__)\000"
-.LASF515:
-	.ascii	"signed +0\000"
 .LASF630:
 	.ascii	"PTRDIFF_MAX (__PTRDIFF_MAX__)\000"
 .LASF838:
@@ -4840,6 +4836,8 @@ main:
 	.ascii	"RCC_CFGR_SW_PLL (0b10)\000"
 .LASF844:
 	.ascii	"PRIXPTR __PRIPTR(X)\000"
+.LASF933:
+	.ascii	"TIM_CR1_CEN_BIT 0\000"
 .LASF797:
 	.ascii	"SCNd64 __SCN64(d)\000"
 .LASF827:
@@ -4918,8 +4916,8 @@ main:
 	.ascii	"__FDPIC__\000"
 .LASF263:
 	.ascii	"__UFRACT_MIN__ 0.0UR\000"
-.LASF688:
-	.ascii	"PRIuLEAST8 __PRI8LEAST(u)\000"
+.LASF515:
+	.ascii	"signed +0\000"
 .LASF213:
 	.ascii	"__FLT32_IS_IEC_60559__ 2\000"
 .LASF629:
@@ -4946,8 +4944,8 @@ main:
 	.ascii	"SCNuLEAST8 __SCN8LEAST(u)\000"
 .LASF102:
 	.ascii	"__UINT8_MAX__ 0xff\000"
-.LASF574:
-	.ascii	"_UINTMAX_T_DECLARED \000"
+.LASF552:
+	.ascii	"___int16_t_defined 1\000"
 .LASF983:
 	.ascii	"timer\000"
 .LASF184:
@@ -5040,6 +5038,8 @@ main:
 	.ascii	"__MISC_VISIBLE 0\000"
 .LASF452:
 	.ascii	"__ELF__ 1\000"
+.LASF688:
+	.ascii	"PRIuLEAST8 __PRI8LEAST(u)\000"
 .LASF969:
 	.ascii	"BDCR\000"
 .LASF853:
@@ -5136,8 +5136,8 @@ main:
 	.ascii	"__ARM_FEATURE_COMPLEX\000"
 .LASF831:
 	.ascii	"PRIXMAX __PRIMAX(X)\000"
-.LASF857:
-	.ascii	"RCC ((struct rcc *) RCC_BASE_ADDR)\000"
+.LASF679:
+	.ascii	"PRIX8 __PRI8(X)\000"
 .LASF523:
 	.ascii	"_INTPTR_EQ_INT \000"
 .LASF408:
@@ -5202,8 +5202,6 @@ main:
 	.ascii	"__FLT_EVAL_METHOD_TS_18661_3__ 0\000"
 .LASF521:
 	.ascii	"int +2\000"
-.LASF1004:
-	.ascii	"/home/alex/code/own/c-compile-experiments\000"
 .LASF636:
 	.ascii	"INT8_C(x) __INT8_C(x)\000"
 .LASF935:
@@ -5454,6 +5452,8 @@ main:
 	.ascii	"__LLFRACT_EPSILON__ 0x1P-63LLR\000"
 .LASF967:
 	.ascii	"APB2LPENR\000"
+.LASF934:
+	.ascii	"TIM_ENABLE (1 << TIM_CR1_CEN_BIT)\000"
 .LASF820:
 	.ascii	"SCNiFAST64 __SCN64FAST(i)\000"
 .LASF537:
@@ -5775,8 +5775,8 @@ main:
 	.ascii	"__UHQ_IBIT__ 0\000"
 .LASF60:
 	.ascii	"__INT_FAST16_TYPE__ int\000"
-.LASF679:
-	.ascii	"PRIX8 __PRI8(X)\000"
+.LASF574:
+	.ascii	"_UINTMAX_T_DECLARED \000"
 .LASF61:
 	.ascii	"__INT_FAST32_TYPE__ int\000"
 .LASF288:
@@ -5870,8 +5870,6 @@ main:
 	.ascii	"__INT_WCHAR_T_H \000"
 .LASF237:
 	.ascii	"__FLT32X_MAX__ 1.7976931348623157e+308F32x\000"
-.LASF552:
-	.ascii	"___int16_t_defined 1\000"
 .LASF438:
 	.ascii	"__ARM_EABI__ 1\000"
 .LASF465:
@@ -6002,8 +6000,6 @@ main:
 	.ascii	"SCNuMAX __SCNMAX(u)\000"
 .LASF121:
 	.ascii	"__UINT16_C(c) c\000"
-.LASF934:
-	.ascii	"TIM4_ENABLE (1 << TIM4_CR_CEN_BIT)\000"
 .LASF359:
 	.ascii	"__UDA_IBIT__ 32\000"
 .LASF534:
@@ -6285,6 +6281,8 @@ main:
 	.ascii	"__SCN64LEAST(x) __LEAST64 __STRINGIFY(x)\000"
 .LASF340:
 	.ascii	"__USQ_FBIT__ 32\000"
+.LASF1004:
+	.ascii	"/home/alex/code/own/stm32-falling-sand\000"
 .LASF796:
 	.ascii	"PRIX64 __PRI64(X)\000"
 .LASF249:
@@ -6337,6 +6335,8 @@ main:
 	.ascii	"__DBL_MANT_DIG__ 53\000"
 .LASF272:
 	.ascii	"__ULFRACT_IBIT__ 0\000"
+.LASF857:
+	.ascii	"RCC ((struct rcc *) RCC_BASE_ADDR)\000"
 .LASF892:
 	.ascii	"RCC_CFGR_HPRE_MASK (0b1111)\000"
 .LASF72:
diff --git a/build/main.i b/build/main.i
index 1404660..e6e6844 100644
--- a/build/main.i
+++ b/build/main.i
@@ -1,5 +1,5 @@
 # 0 "src/main.c"
-# 1 "/home/alex/code/own/c-compile-experiments//"
+# 1 "/home/alex/code/own/stm32-falling-sand//"
 # 0 "<built-in>"
 #define __STDC__ 1
 # 0 "<built-in>"
@@ -2237,8 +2237,8 @@ struct timer {
 #define TIM4_BASE_ADDR (0x40000800U)
 #define TIM4 ((struct timer *) TIM4_BASE_ADDR)
 
-#define TIM4_CR_CEN_BIT 0
-#define TIM4_ENABLE (1 << TIM4_CR_CEN_BIT)
+#define TIM_CR1_CEN_BIT 0
+#define TIM_ENABLE (1 << TIM_CR1_CEN_BIT)
 
 void tim4_init(void);
 void tim4_start(void);
diff --git a/build/main.o b/build/main.o
index 7baa25a..87460c9 100644
Binary files a/build/main.o and b/build/main.o differ
diff --git a/build/startup.S b/build/startup.S
index 0e7baf8..f652787 100644
--- a/build/startup.S
+++ b/build/startup.S
@@ -2923,6 +2923,8 @@ interrupt_vector_table:
 	.ascii	"INOR__ >= ((maj) << 16) + (min))\000"
 .LASF171:
 	.ascii	"__DBL_MAX__ ((double)1.7976931348623157e+308L)\000"
+.LASF602:
+	.ascii	"UINTMAX_C(x) __UINTMAX_C(x)\000"
 .LASF253:
 	.ascii	"__USFRACT_MIN__ 0.0UHR\000"
 .LASF578:
@@ -3020,8 +3022,8 @@ interrupt_vector_table:
 	.ascii	"__BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__\000"
 .LASF200:
 	.ascii	"__FLT32_MIN_10_EXP__ (-37)\000"
-.LASF176:
-	.ascii	"__DBL_HAS_DENORM__ 1\000"
+.LASF492:
+	.ascii	"__int20\000"
 .LASF267:
 	.ascii	"__LFRACT_IBIT__ 0\000"
 .LASF497:
@@ -3106,8 +3108,8 @@ interrupt_vector_table:
 	.ascii	"__ARM_NEON\000"
 .LASF401:
 	.ascii	"__ARM_FEATURE_CMSE\000"
-.LASF625:
-	.ascii	"/home/alex/code/own/c-compile-experiments\000"
+.LASF68:
+	.ascii	"__UINTPTR_TYPE__ unsigned int\000"
 .LASF229:
 	.ascii	"__FLT64_IS_IEC_60559__ 2\000"
 .LASF209:
@@ -3473,8 +3475,6 @@ interrupt_vector_table:
 	.ascii	"UINT16_C(x) __UINT16_C(x)\000"
 .LASF344:
 	.ascii	"__UTQ_FBIT__ 128\000"
-.LASF499:
-	.ascii	"__int20 +2\000"
 .LASF610:
 	.ascii	"long long int\000"
 .LASF24:
@@ -3539,8 +3539,8 @@ interrupt_vector_table:
 	.ascii	"__STDC__ 1\000"
 .LASF17:
 	.ascii	"__SIZEOF_LONG__ 4\000"
-.LASF492:
-	.ascii	"__int20\000"
+.LASF499:
+	.ascii	"__int20 +2\000"
 .LASF168:
 	.ascii	"__DBL_MAX_EXP__ 1024\000"
 .LASF585:
@@ -3567,6 +3567,8 @@ interrupt_vector_table:
 	.ascii	"__SCHAR_WIDTH__ 8\000"
 .LASF298:
 	.ascii	"__ACCUM_MIN__ (-0X1P15K-0X1P15K)\000"
+.LASF40:
+	.ascii	"__CHAR16_TYPE__ short unsigned int\000"
 .LASF21:
 	.ascii	"__SIZEOF_DOUBLE__ 8\000"
 .LASF7:
@@ -3801,8 +3803,8 @@ interrupt_vector_table:
 	.ascii	"SIZE_MAX (__SIZE_MAX__)\000"
 .LASF54:
 	.ascii	"__INT_LEAST64_TYPE__ long long int\000"
-.LASF602:
-	.ascii	"UINTMAX_C(x) __UINTMAX_C(x)\000"
+.LASF128:
+	.ascii	"__INT_FAST16_MAX__ 0x7fffffff\000"
 .LASF49:
 	.ascii	"__UINT32_TYPE__ long unsigned int\000"
 .LASF183:
@@ -3879,8 +3881,8 @@ interrupt_vector_table:
 	.ascii	"INT64_MAX (__INT64_MAX__)\000"
 .LASF518:
 	.ascii	"_INT8_T_DECLARED \000"
-.LASF40:
-	.ascii	"__CHAR16_TYPE__ short unsigned int\000"
+.LASF625:
+	.ascii	"/home/alex/code/own/stm32-falling-sand\000"
 .LASF370:
 	.ascii	"__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1\000"
 .LASF151:
@@ -4044,8 +4046,8 @@ interrupt_vector_table:
 	.ascii	"__FLT32X_MAX_10_EXP__ 308\000"
 .LASF140:
 	.ascii	"__UINTPTR_MAX__ 0xffffffffU\000"
-.LASF128:
-	.ascii	"__INT_FAST16_MAX__ 0x7fffffff\000"
+.LASF176:
+	.ascii	"__DBL_HAS_DENORM__ 1\000"
 .LASF32:
 	.ascii	"__GNUC_EXECUTION_CHARSET_NAME \"UTF-8\"\000"
 .LASF475:
@@ -4072,8 +4074,6 @@ interrupt_vector_table:
 	.ascii	"long +4\000"
 .LASF534:
 	.ascii	"__int_least8_t_defined 1\000"
-.LASF68:
-	.ascii	"__UINTPTR_TYPE__ unsigned int\000"
 .LASF92:
 	.ascii	"__UINTMAX_MAX__ 0xffffffffffffffffULL\000"
 .LASF42:
diff --git a/build/startup.i b/build/startup.i
index a43bdc7..1d70ec9 100644
--- a/build/startup.i
+++ b/build/startup.i
@@ -1,5 +1,5 @@
 # 0 "src/startup.c"
-# 1 "/home/alex/code/own/c-compile-experiments//"
+# 1 "/home/alex/code/own/stm32-falling-sand//"
 # 0 "<built-in>"
 #define __STDC__ 1
 # 0 "<built-in>"
diff --git a/build/startup.o b/build/startup.o
index fd68f1d..7f8da75 100644
Binary files a/build/startup.o and b/build/startup.o differ
diff --git a/build/timer.S b/build/timer.S
index 4ff166a..25a5850 100644
--- a/build/timer.S
+++ b/build/timer.S
@@ -3650,7 +3650,7 @@ tim4_start:
 	.uleb128 0x7a
 	.4byte	.LASF898
 	.byte	0
-	.section	.debug_macro,"G",%progbits,wm4.timer.h.2.a5bec0ee8e2998a7b121820fb4e4e9a6,comdat
+	.section	.debug_macro,"G",%progbits,wm4.timer.h.2.2e929ede818fb0960868f1b0a08a1cbf,comdat
 .Ldebug_macro15:
 	.2byte	0x5
 	.byte	0
@@ -3673,8 +3673,6 @@ tim4_start:
 	.section	.debug_line,"",%progbits
 .Ldebug_line0:
 	.section	.debug_str,"MS",%progbits,1
-.LASF902:
-	.ascii	"TIM4_CR_CEN_BIT 0\000"
 .LASF735:
 	.ascii	"SCNxLEAST16 __SCN16LEAST(x)\000"
 .LASF636:
@@ -3822,8 +3820,6 @@ tim4_start:
 	.ascii	"PRIx8 __PRI8(x)\000"
 .LASF590:
 	.ascii	"INT8_MAX (__INT8_MAX__)\000"
-.LASF516:
-	.ascii	"signed +0\000"
 .LASF631:
 	.ascii	"PTRDIFF_MAX (__PTRDIFF_MAX__)\000"
 .LASF839:
@@ -4168,6 +4164,8 @@ tim4_start:
 	.ascii	"SCNoLEAST32 __SCN32LEAST(o)\000"
 .LASF891:
 	.ascii	"RCC_CFGR_SW_PLL (0b10)\000"
+.LASF902:
+	.ascii	"TIM_CR1_CEN_BIT 0\000"
 .LASF798:
 	.ascii	"SCNd64 __SCN64(d)\000"
 .LASF828:
@@ -4242,8 +4240,8 @@ tim4_start:
 	.ascii	"__FDPIC__\000"
 .LASF263:
 	.ascii	"__UFRACT_MIN__ 0.0UR\000"
-.LASF689:
-	.ascii	"PRIuLEAST8 __PRI8LEAST(u)\000"
+.LASF516:
+	.ascii	"signed +0\000"
 .LASF213:
 	.ascii	"__FLT32_IS_IEC_60559__ 2\000"
 .LASF630:
@@ -4352,6 +4350,8 @@ tim4_start:
 	.ascii	"__MISC_VISIBLE 0\000"
 .LASF306:
 	.ascii	"__LACCUM_FBIT__ 31\000"
+.LASF689:
+	.ascii	"PRIuLEAST8 __PRI8LEAST(u)\000"
 .LASF937:
 	.ascii	"BDCR\000"
 .LASF211:
@@ -4510,8 +4510,6 @@ tim4_start:
 	.ascii	"__FLT_EVAL_METHOD_TS_18661_3__ 0\000"
 .LASF522:
 	.ascii	"int +2\000"
-.LASF958:
-	.ascii	"/home/alex/code/own/c-compile-experiments\000"
 .LASF637:
 	.ascii	"INT8_C(x) __INT8_C(x)\000"
 .LASF63:
@@ -4752,6 +4750,8 @@ tim4_start:
 	.ascii	"__LLFRACT_EPSILON__ 0x1P-63LLR\000"
 .LASF935:
 	.ascii	"APB2LPENR\000"
+.LASF903:
+	.ascii	"TIM_ENABLE (1 << TIM_CR1_CEN_BIT)\000"
 .LASF821:
 	.ascii	"SCNiFAST64 __SCN64FAST(i)\000"
 .LASF538:
@@ -5275,8 +5275,6 @@ tim4_start:
 	.ascii	"SCNuMAX __SCNMAX(u)\000"
 .LASF121:
 	.ascii	"__UINT16_C(c) c\000"
-.LASF903:
-	.ascii	"TIM4_ENABLE (1 << TIM4_CR_CEN_BIT)\000"
 .LASF359:
 	.ascii	"__UDA_IBIT__ 32\000"
 .LASF535:
@@ -5541,6 +5539,8 @@ tim4_start:
 	.ascii	"__SCN64LEAST(x) __LEAST64 __STRINGIFY(x)\000"
 .LASF340:
 	.ascii	"__USQ_FBIT__ 32\000"
+.LASF958:
+	.ascii	"/home/alex/code/own/stm32-falling-sand\000"
 .LASF797:
 	.ascii	"PRIX64 __PRI64(X)\000"
 .LASF249:
diff --git a/build/timer.i b/build/timer.i
index 74f1085..c8a2bbe 100644
--- a/build/timer.i
+++ b/build/timer.i
@@ -1,5 +1,5 @@
 # 0 "src/timer.c"
-# 1 "/home/alex/code/own/c-compile-experiments//"
+# 1 "/home/alex/code/own/stm32-falling-sand//"
 # 0 "<built-in>"
 #define __STDC__ 1
 # 0 "<built-in>"
@@ -2120,8 +2120,8 @@ struct timer {
 #define TIM4_BASE_ADDR (0x40000800U)
 #define TIM4 ((struct timer *) TIM4_BASE_ADDR)
 
-#define TIM4_CR_CEN_BIT 0
-#define TIM4_ENABLE (1 << TIM4_CR_CEN_BIT)
+#define TIM_CR1_CEN_BIT 0
+#define TIM_ENABLE (1 << TIM_CR1_CEN_BIT)
 
 void tim4_init(void);
 void tim4_start(void);
diff --git a/build/timer.o b/build/timer.o
index e731214..917c295 100644
Binary files a/build/timer.o and b/build/timer.o differ
diff --git a/src/timer.c b/src/timer.c
index cb794d3..0bec1bd 100644
--- a/src/timer.c
+++ b/src/timer.c
@@ -18,5 +18,5 @@ void tim4_init(void) {
 }
 
 void tim4_start(void) {
-  TIM4->CR1 |= TIM4_ENABLE;
+  TIM4->CR1 |= TIM_ENABLE;
 }
diff --git a/src/timer.h b/src/timer.h
index 18eebc4..3b386de 100644
--- a/src/timer.h
+++ b/src/timer.h
@@ -29,8 +29,8 @@ struct timer {
 #define TIM4_BASE_ADDR (0x40000800U)
 #define TIM4 ((struct timer *) TIM4_BASE_ADDR)
 
-#define TIM4_CR_CEN_BIT 0
-#define TIM4_ENABLE (1 << TIM4_CR_CEN_BIT)
+#define TIM_CR1_CEN_BIT 0
+#define TIM_ENABLE (1 << TIM_CR1_CEN_BIT)
 
 void tim4_init(void);
 void tim4_start(void);