diff options
| author | Keith Packard <keithp@keithp.com> | 2017-09-12 13:40:06 -0700 |
|---|---|---|
| committer | Keith Packard <keithp@keithp.com> | 2017-09-12 13:40:06 -0700 |
| commit | 10d14146ef84fbe4670454bc0996854a4066cfea (patch) | |
| tree | 1e9c4b3b374dc0739dbc347db6193977b8d28ab6 | |
| parent | 8284ba8bf78aade8f9d8f711cfefe2010ce81066 (diff) | |
chaoskey: Wait for input data to stabilize before using it
The ADC data takes a while to start working after power on; wait for
the range of input values to look reasonable before using the data.
Signed-off-by: Keith Packard <keithp@keithp.com>
| -rw-r--r-- | src/drivers/ao_trng_send.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/src/drivers/ao_trng_send.c b/src/drivers/ao_trng_send.c index b1227aaa..7cda053d 100644 --- a/src/drivers/ao_trng_send.c +++ b/src/drivers/ao_trng_send.c @@ -153,10 +153,20 @@ ao_trng_send(void) ao_crc_reset(); - ao_delay(TRNG_ENABLE_DELAY); - for (s = 0; s < AO_TRNG_START_WAIT; s++) { - if (ao_trng_get_cooked(buffer[0])) + int i; + uint16_t min, max; + uint16_t buf[AO_USB_IN_SIZE>>1]; + + ao_trng_get_raw(buf); + min = max = buf[0]; + for (i = 1; i < (AO_USB_IN_SIZE>>1); i++) { + uint16_t v = buf[i]; + if (v < min) min = v; + if (v > max) max = v; + } + /* Wait for at least 10 bits of range */ + if ((uint16_t) (max - min) >= 1024) break; ao_delay(AO_MS_TO_TICKS(10)); } |