diff options
Diffstat (limited to 'src/occ_gpe0/apss_util.c')
| -rw-r--r-- | src/occ_gpe0/apss_util.c | 34 |
1 files changed, 28 insertions, 6 deletions
diff --git a/src/occ_gpe0/apss_util.c b/src/occ_gpe0/apss_util.c index 2a78561..04e9879 100644 --- a/src/occ_gpe0/apss_util.c +++ b/src/occ_gpe0/apss_util.c @@ -115,17 +115,39 @@ int wait_spi_completion(GpeErrorStruct *error, uint32_t reg, uint8_t timeout) * End Function Specification */ -// result based on busy_wait(1) calibration against pk_sleep(1) -#define BUSY_LOOP_CONSTANT 71 void busy_wait(uint32_t t_microseconds) { int j; volatile uint32_t i; -// ppe42_mullw macro works fine, but compiler parameter settings seems broken, use nested loop instead -// int loop = t * 100; // Assuming loop iteration takes 6 ppe cycles = 0.01 microseconds - for(j = 0; j < BUSY_LOOP_CONSTANT; j++) - for(i = 0; i < t_microseconds; i++); + uint32_t start_decrementer_value; // The decrementer register value at the beginning + uint32_t end_decrementer_value; // The decrementer register value at the end + uint32_t current_decrementer_value; // The current decrementer register value + uint32_t duration; + MFDEC(start_decrementer_value); // get the decrementer register value at the beginning + current_decrementer_value = start_decrementer_value; + + // multiply the delay time by the 37.5 MHz external clock frequency. + // I believe that the ppe42_mullw macro works fine, but the + // compiler parameter settings seems broken. + // @todo: This is a temporary fix, use external frequency directive. + duration = (t_microseconds << 5) + + (t_microseconds << 2) + + (t_microseconds) + + (t_microseconds >> 1); + + // Calculate the decrementer register value at the end of the busy wait period + end_decrementer_value = start_decrementer_value - duration; + + if(start_decrementer_value < end_decrementer_value); // decrementer overflows during the busy wait? + { + MFDEC(current_decrementer_value); + while(current_decrementer_value < end_decrementer_value) // Wait until Decrementer overflows + MFDEC(current_decrementer_value); + } + + while (current_decrementer_value > end_decrementer_value) // Wait until end_decrementer_value is reached + MFDEC(current_decrementer_value); } |
