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floppy: Implement 50us mask after every /IDX falling edge, to prevent

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false index triggering on erratic/bouncy index sensors.
Refs #52
This commit is contained in:
Keir Fraser
2020-08-09 12:56:15 +01:00
parent d1e1ad4b1f
commit ff635cf5b7
1 changed files with 33 additions and 1 deletions
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34
src/floppy.c
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@@ -54,8 +54,16 @@ static struct index {
volatile unsigned int count;
/* For synchronising index pulse reporting to the RDATA flux stream. */
volatile unsigned int rdata_cnt;
/* Last time at which ISR fired. */
time_t isr_time;
/* Timer structure for index_timer() calls. */
struct timer timer;
} index;
/* Timer to clean up stale index.isr_time. */
#define INDEX_TIMER_PERIOD time_ms(5000)
static void index_timer(void *unused);
/* A DMA buffer for running a timer associated with a floppy-data I/O pin. */
static struct dma_ring {
/* Indexes into the buf[] ring buffer. */
@@ -233,6 +241,8 @@ void floppy_init(void)
configure_pin(wrprot, GPI_bus);
/* Configure INDEX-changed IRQs and timer. */
timer_init(&index.timer, index_timer, NULL);
index_timer(NULL);
exti->rtsr = 0;
exti->imr = exti->ftsr = m(pin_index);
IRQx_set_prio(irq_index, INDEX_IRQ_PRI);
@@ -1217,11 +1227,33 @@ const struct usb_class_ops usb_cdc_acm_ops = {
static void IRQ_INDEX_changed(void)
{
unsigned int cnt = tim_rdata->cnt;
time_t now = time_now(), prev = index.isr_time;
/* Clear INDEX-changed flag. */
exti->pr = m(pin_index);
index.isr_time = now;
if (time_diff(prev, now) < time_us(50))
return;
index.count++;
index.rdata_cnt = tim_rdata->cnt;
index.rdata_cnt = cnt;
}
static void index_timer(void *unused)
{
time_t now = time_now();
IRQ_global_disable();
/* index.isr_time mustn't get so old that the time_diff() test in
* IRQ_INDEX_changed() overflows. To prevent this, we ensure that,
* at all times,
* time_diff(index.isr_time, time_now()) < 2*INDEX_TIMER_PERIOD + delta,
* where delta is small. */
if (time_diff(index.isr_time, now) > INDEX_TIMER_PERIOD)
index.isr_time = now - INDEX_TIMER_PERIOD;
IRQ_global_enable();
timer_set(&index.timer, now + INDEX_TIMER_PERIOD);
}
/*