Mercurial > ~darius > hgwebdir.cgi > stm32temp
diff delay.c @ 40:a38003b97de6
Use debug cycle counter to handle delays.
| author | Daniel O'Connor <darius@dons.net.au> |
|---|---|
| date | Mon, 01 Apr 2013 20:06:03 +1030 |
| parents | 891841f5f785 |
| children | cecb0506f4b8 |
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--- a/delay.c Mon Apr 01 19:45:38 2013 +1030 +++ b/delay.c Mon Apr 01 20:06:03 2013 +1030 @@ -1,83 +1,36 @@ +#include <assert.h> #include <stdint.h> #include "stm32f10x.h" #include "delay.h" /* Sleep for nCount usec - * TDS1012 on 2.5usec/div shows... - * 30usec = 29.60usec - * 60usec = 59.20usec - * - * XXX: not sure disable IRQ stuff is working as I see occasional (small) extra delays */ void delay(uint32_t nCount) { - __disable_irq(); - for(; nCount != 0; nCount--) { -#ifdef SYSCLK_FREQ_72MHz - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); + uint32_t dly, cnt, clk_per_usec, max_dly; + volatile uint32_t *DWT_CYCCNT = (uint32_t *)0xe0001004; - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); + __disable_irq(); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); - __asm__("nop"); +#ifdef SYSCLK_FREQ_72MHz + clk_per_usec = 72; + max_dly = (1<<31) / clk_per_usec; /* Really half the maximum (still ~30 seconds at 72MHz) */ #else -#error Unknown clock frequency +#error "Unknown clock frequency" #endif - } + assert(nCount < max_dly); + + cnt = *DWT_CYCCNT; /* Get current cycle count */ + dly = nCount * clk_per_usec; + dly += cnt; /* Compute cycle count to stop at */ + if (dly < cnt) + /* Stop count wrapped, wait until the counter wraps around */ + while (*DWT_CYCCNT > cnt) + ; + /* Wait until we get to the stop count */ + while (*DWT_CYCCNT < dly) + ; + __enable_irq(); }