2 * Copyright © 2015 Keith Packard <keithp@keithp.com>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; version 2 of the License.
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
13 * You should have received a copy of the GNU General Public License along
14 * with this program; if not, write to the Free Software Foundation, Inc.,
15 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
19 #include <ao_adc_fast.h>
21 #include <ao_trng_send.h>
25 static uint8_t trng_running;
26 static AO_TICK_TYPE trng_power_time;
28 /* Make sure there's at least 8 bits of variance in the samples */
29 #define MIN_VARIANCE (128 * 128)
31 #define DECLARE_STATS int32_t sum = 0, sum2 = 0
33 #define ADD_STATS(value) do { \
35 sum2 += (value) * (value); \
38 #define GOOD_STATS(i) (((sum2 - (sum * sum) / i) / i) >= MIN_VARIANCE)
40 #define TRNG_ENABLE_DELAY AO_MS_TO_TICKS(100)
43 ao_trng_send_raw(uint16_t *buf)
51 t = ao_adc_get(AO_USB_IN_SIZE>>1); /* one 16-bit value per two output bytes */
52 for (i = 0; i < AO_USB_IN_SIZE / sizeof (uint16_t); i++) {
55 t = (t + 1) & (AO_ADC_RING_SIZE - 1);
59 return GOOD_STATS(AO_USB_IN_SIZE / sizeof (uint16_t));
63 ao_trng_send_cooked(uint16_t *buf)
67 uint32_t *rnd = (uint32_t *) ao_adc_ring;
71 t = ao_adc_get(AO_USB_IN_SIZE) >> 1; /* one 16-bit value per output byte */
73 for (i = 0; i < AO_USB_IN_SIZE / sizeof (uint16_t); i++) {
77 /* Fetch two values in one operation */
79 t = (t + 1) & ((AO_ADC_RING_SIZE >> 1) - 1);
81 *buf++ = ao_crc_in_32_out_16(v);
89 return GOOD_STATS(2 * AO_USB_IN_SIZE / sizeof (uint16_t));
95 return !ao_gpio_get(AO_RAW_PORT, AO_RAW_BIT, AO_RAW_PIN);
101 static uint16_t *buffer[2];
107 buffer[0] = ao_usb_alloc();
108 buffer[1] = ao_usb_alloc();
115 #ifdef AO_TRNG_ENABLE_PORT
116 ao_gpio_set(AO_TRNG_ENABLE_PORT, AO_TRNG_ENABLE_BIT, AO_TRNG_ENABLE_PIN, 1);
118 trng_power_time = ao_time();
126 delay = trng_power_time + TRNG_ENABLE_DELAY - ao_time();
127 if (delay > TRNG_ENABLE_DELAY)
128 delay = TRNG_ENABLE_DELAY;
130 /* Delay long enough for the HV power supply
131 * to stabilize so that the first bits we read
132 * aren't of poor quality
138 ao_led_on(AO_LED_TRNG_RAW);
139 good_bits = ao_trng_send_raw(buffer[usb_buf_id]);
140 ao_led_off(AO_LED_TRNG_RAW);
142 ao_led_on(AO_LED_TRNG_COOKED);
143 good_bits = ao_trng_send_cooked(buffer[usb_buf_id]);
144 ao_led_off(AO_LED_TRNG_COOKED);
146 ao_adc_ack(AO_USB_IN_SIZE);
148 ao_usb_write(buffer[usb_buf_id], AO_USB_IN_SIZE);
149 usb_buf_id = 1-usb_buf_id;
153 ao_delay(AO_MS_TO_TICKS(10));
156 ao_panic(AO_PANIC_DMA);
162 static struct ao_task ao_trng_send_task;
164 #if AO_POWER_MANAGEMENT
166 static void ao_trng_suspend(void *arg)
169 #ifdef AO_TRNG_ENABLE_PORT
170 ao_gpio_set(AO_TRNG_ENABLE_PORT, AO_TRNG_ENABLE_BIT, AO_TRNG_ENABLE_PIN, 0);
172 trng_running = FALSE;
175 static void ao_trng_resume(void *arg)
178 #ifdef AO_TRNG_ENABLE_PORT
179 ao_gpio_set(AO_TRNG_ENABLE_PORT, AO_TRNG_ENABLE_BIT, AO_TRNG_ENABLE_PIN, 1);
181 trng_power_time = ao_time();
184 static struct ao_power ao_trng_power = {
185 .suspend = ao_trng_suspend,
186 .resume = ao_trng_resume
192 ao_trng_send_init(void)
194 #ifdef AO_TRNG_ENABLE_PORT
195 ao_enable_output(AO_TRNG_ENABLE_PORT, AO_TRNG_ENABLE_BIT, AO_TRNG_ENABLE_PIN, 0);
196 ao_power_register(&ao_trng_power);
198 ao_enable_input(AO_RAW_PORT, AO_RAW_BIT, AO_EXTI_MODE_PULL_UP);
199 ao_add_task(&ao_trng_send_task, ao_trng_send, "trng_send");