+#include <ao_exti.h>
+#include <ao_power.h>
+
+static uint8_t trng_running;
+static AO_TICK_TYPE trng_power_time;
+
+/* Make sure there's at least 8 bits of variance in the samples */
+#define MIN_VARIANCE (128 * 128)
+
+#define DECLARE_STATS int32_t sum = 0, sum2 = 0
+
+#define ADD_STATS(value) do { \
+ sum += (value); \
+ sum2 += (value) * (value); \
+ } while(0)
+
+#define GOOD_STATS(i) (((sum2 - (sum * sum) / i) / i) >= MIN_VARIANCE)
+
+#define TRNG_ENABLE_DELAY AO_MS_TO_TICKS(100)
+
+static int
+ao_trng_send_raw(uint16_t *buf)
+{
+ uint16_t i;
+ uint16_t t;
+ uint16_t v;
+
+ DECLARE_STATS;
+
+ t = ao_adc_get(AO_USB_IN_SIZE>>1); /* one 16-bit value per two output bytes */
+ for (i = 0; i < AO_USB_IN_SIZE / sizeof (uint16_t); i++) {
+ v = ao_adc_ring[t];
+ *buf++ = v;
+ t = (t + 1) & (AO_ADC_RING_SIZE - 1);
+
+ ADD_STATS(v);
+ }
+ return GOOD_STATS(AO_USB_IN_SIZE / sizeof (uint16_t));
+}
+
+static int
+ao_trng_send_cooked(uint16_t *buf)
+{
+ uint16_t i;
+ uint16_t t;
+ uint32_t *rnd = (uint32_t *) ao_adc_ring;
+
+ DECLARE_STATS;
+
+ t = ao_adc_get(AO_USB_IN_SIZE) >> 1; /* one 16-bit value per output byte */
+
+ for (i = 0; i < AO_USB_IN_SIZE / sizeof (uint16_t); i++) {
+ uint32_t v;
+ uint16_t v1, v2;
+
+ /* Fetch two values in one operation */
+ v = rnd[t];
+ t = (t + 1) & ((AO_ADC_RING_SIZE >> 1) - 1);
+
+ *buf++ = ao_crc_in_32_out_16(v);
+
+ v1 = v;
+ v2 = v >> 16;
+
+ ADD_STATS(v1);
+ ADD_STATS(v2);
+ }
+ return GOOD_STATS(2 * AO_USB_IN_SIZE / sizeof (uint16_t));
+}
+
+static inline int
+ao_send_raw(void)
+{
+ return !ao_gpio_get(AO_RAW_PORT, AO_RAW_BIT, AO_RAW_PIN);
+}