uint32_t IRAM_ATTR esp_random(void) { /* The PRNG which implements WDEV_RANDOM register gets 2 bits * of extra entropy from a hardware randomness source every APB clock cycle * (provided WiFi or BT are enabled). To make sure entropy is not drained * faster than it is added, this function needs to wait for at least 16 APB * clock cycles after reading previous word. This implementation may actually * wait a bit longer due to extra time spent in arithmetic and branch statements. * * As a (probably unncessary) precaution to avoid returning the * RNG state as-is, the result is XORed with additional * WDEV_RND_REG reads while waiting. */ /* This code does not run in a critical section, so CPU frequency switch may * happens while this code runs (this will not happen in the current * implementation, but possible in the future). However if that happens, * the number of cycles spent on frequency switching will certainly be more * than the number of cycles we need to wait here. */ uint32_t cpu_to_apb_freq_ratio = esp_clk_cpu_freq() / esp_clk_apb_freq(); static uint32_t last_ccount = 0; uint32_t ccount; uint32_t result = 0; do { ccount = XTHAL_GET_CCOUNT(); result ^= REG_READ(WDEV_RND_REG); } while (ccount - last_ccount < cpu_to_apb_freq_ratio * 16); last_ccount = ccount; return result ^ REG_READ(WDEV_RND_REG); }
uint32_t unity_exec_time_get_ms(void) { return (s_test_stop - s_test_start) / (esp_clk_cpu_freq() / 1000); }