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

[fw/altos] / src / drivers / ao_trng_send.c

diff --git a/src/drivers/ao_trng_send.c b/src/drivers/ao_trng_send.c
index 63366d3ef53baad6f4b9f0f2a107aeea0c76a79b..11f441f897e5ada0b393fed94fb2b3a5be872616 100644 (file)
--- 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);