diff options
| author | Keith Packard <keithp@keithp.com> | 2015-03-20 15:09:20 -0700 |
|---|---|---|
| committer | Keith Packard <keithp@keithp.com> | 2015-03-20 15:09:20 -0700 |
| commit | b1b69c8b73cbffb56c688f6a968d144b642cdff2 (patch) | |
| tree | e54eb4ccbed98014a6ccce31d6144b5a3e2866f1 /src/drivers/ao_trng_send.c | |
| parent | 43b4044dc71d44cb25be6397b4d66fd792580eed (diff) | |
altos/stmf0: Have fast ADC ring buffer code use wrap-around
Instead of requiring that the whole set of returned values fit
precisely in the ring, allow for wrap-around so that we can fetch an
odd number of ADC values. The previous version required that the fetch
amount always be a factor of the ADC buffer size.
Signed-off-by: Keith Packard <keithp@keithp.com>
Diffstat (limited to 'src/drivers/ao_trng_send.c')
| -rw-r--r-- | src/drivers/ao_trng_send.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/src/drivers/ao_trng_send.c b/src/drivers/ao_trng_send.c index 34a8a981..bac6035c 100644 --- a/src/drivers/ao_trng_send.c +++ b/src/drivers/ao_trng_send.c @@ -27,7 +27,8 @@ ao_trng_send(void) int usb_buf_id; uint16_t i; uint16_t *buf; - uint32_t *rnd; + uint16_t t; + uint32_t *rnd = (uint32_t *) ao_adc_ring; if (!buffer[0]) { buffer[0] = ao_usb_alloc(); @@ -42,10 +43,12 @@ ao_trng_send(void) for (;;) { ao_led_on(AO_LED_TRNG_ACTIVE); - rnd = (uint32_t *) ao_adc_get(AO_USB_IN_SIZE); /* one 16-bit value per output byte */ + t = ao_adc_get(AO_USB_IN_SIZE) >> 1; /* one 16-bit value per output byte */ buf = buffer[usb_buf_id]; - for (i = 0; i < AO_USB_IN_SIZE / sizeof (uint16_t); i++) - *buf++ = ao_crc_in_32_out_16(*rnd++); + for (i = 0; i < AO_USB_IN_SIZE / sizeof (uint16_t); i++) { + *buf++ = ao_crc_in_32_out_16(rnd[t]); + t = (t + 1) & ((AO_ADC_RING_SIZE>>1) - 1); + } ao_adc_ack(AO_USB_IN_SIZE); ao_led_off(AO_LED_TRNG_ACTIVE); ao_usb_write(buffer[usb_buf_id], AO_USB_IN_SIZE); |