From: Keith Packard <keithp@keithp.com>
Date: Sun, 7 Feb 2016 23:33:42 +0000 (-0800)
Subject: altos: Delay TRNG ADC long enough for HV supply to stabilize
X-Git-Tag: 1.6.3~2^2~104
X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=commitdiff_plain;h=147f0df6a29b37fbfb0824ecd276482f0eecb397

altos: Delay TRNG ADC long enough for HV supply to stabilize

Looks like it takes about 70ms for the supply to start running right,
so delay after powering it up for that long.

Signed-off-by: Keith Packard <keithp@keithp.com>
---

diff --git a/src/drivers/ao_trng_send.c b/src/drivers/ao_trng_send.c
index 63366d3e..11f441f8 100644
--- a/src/drivers/ao_trng_send.c
+++ b/src/drivers/ao_trng_send.c
@@ -22,7 +22,8 @@
 #include <ao_exti.h>
 #include <ao_power.h>
 
-static uint8_t	trng_running;
+static uint8_t		trng_running;
+static AO_TICK_TYPE	trng_power_time;
 
 static void
 ao_trng_send_raw(uint16_t *buf)
@@ -45,7 +46,7 @@ ao_trng_send_cooked(uint16_t *buf)
 	uint16_t	t;
 	uint32_t	*rnd = (uint32_t *) ao_adc_ring;
 
-	t = ao_adc_get(AO_USB_IN_SIZE) >> 1;	/* one 16-bit value per output byte */
+	t = ao_adc_get(AO_USB_IN_SIZE) >> 1;	/* two 16-bit values per two output bytes */
 	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);
@@ -73,15 +74,26 @@ ao_trng_send(void)
 
 	usb_buf_id = 0;
 
+#ifdef AO_TRNG_ENABLE_PORT
+	ao_gpio_set(AO_TRNG_ENABLE_PORT, AO_TRNG_ENABLE_BIT, AO_TRNG_ENABLE_PIN, 1);
+#endif
+	trng_power_time = ao_time();
+
 	ao_crc_reset();
 
 	for (;;) {
 		if (!trng_running) {
+			AO_TICK_TYPE	delay;
+
+			delay = trng_power_time + AO_MS_TO_TICKS(100) - ao_time();
+			if (delay > AO_MS_TO_TICKS(100))
+				delay = AO_MS_TO_TICKS(100);
+
 			/* Delay long enough for the HV power supply
 			 * to stabilize so that the first bits we read
 			 * aren't of poor quality
 			 */
-			ao_delay(AO_MS_TO_TICKS(10));
+			ao_delay(delay);
 			trng_running = TRUE;
 		}
 		if (ao_send_raw()) {
@@ -118,6 +130,7 @@ static void ao_trng_resume(void *arg)
 #ifdef AO_TRNG_ENABLE_PORT
 	ao_gpio_set(AO_TRNG_ENABLE_PORT, AO_TRNG_ENABLE_BIT, AO_TRNG_ENABLE_PIN, 1);
 #endif
+	trng_power_time = ao_time();
 }
 
 static struct ao_power ao_trng_power = {
@@ -131,7 +144,7 @@ void
 ao_trng_send_init(void)
 {
 #ifdef AO_TRNG_ENABLE_PORT
-	ao_enable_output(AO_TRNG_ENABLE_PORT, AO_TRNG_ENABLE_BIT, AO_TRNG_ENABLE_PIN, 1);
+	ao_enable_output(AO_TRNG_ENABLE_PORT, AO_TRNG_ENABLE_BIT, AO_TRNG_ENABLE_PIN, 0);
 	ao_power_register(&ao_trng_power);
 #endif
 	ao_enable_input(AO_RAW_PORT, AO_RAW_BIT, AO_EXTI_MODE_PULL_UP);