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Choose buffer size/count to maintain packet rate to WS client at different sample rates

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This commit is contained in:
Matt
2025-12-13 11:21:09 +00:00
parent 74dd3646b5
commit 33f3360a4b
2 changed files with 52 additions and 18 deletions
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44
main/main.c
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@@ -82,6 +82,25 @@ static void continuous_adc_init(adc_channel_t *channel, uint8_t channel_num,
adc_continuous_handle_t *out_handle);
static esp_err_t ws_handler(httpd_req_t *req);
// Forward declarations
static void wifi_init_sta(void);
static void continuous_adc_init(adc_channel_t *channel, uint8_t channel_num,
adc_continuous_handle_t *out_handle);
static esp_err_t ws_handler(httpd_req_t *req);
// Helper to calculate optimal buffer size (approx 50ms latency, max 4096, aligned to 4)
static uint32_t get_optimal_buffer_size(uint32_t sample_rate) {
uint32_t bytes_per_sec = sample_rate * sizeof(adc_digi_output_data_t);
uint32_t target_size = bytes_per_sec / 50; // 20ms (50Hz)
// Clamp to min/max
if (target_size < 128) target_size = 128;
if (target_size > ADC_READ_LEN) target_size = ADC_READ_LEN;
// Align to 4 bytes
return (target_size + 3) & ~3;
}
/*
* Task to read from ADC Continuous driver
*/
@@ -134,7 +153,7 @@ static void adc_read_task(void *arg) {
s_reconfig_needed = false;
}
ret = adc_continuous_read(adc_handle, result, ADC_READ_LEN, &ret_num, 0);
ret = adc_continuous_read(adc_handle, result, get_optimal_buffer_size(s_sample_rate), &ret_num, 0);
if (ret == ESP_OK) {
// ESP_LOGI(TAG, "ret is %x, ret_num is %"PRIu32" bytes", ret, ret_num);
@@ -172,11 +191,12 @@ static void adc_read_task(void *arg) {
// Non-blocking send (best effort)
esp_err_t ret_ws = httpd_ws_send_frame_async(s_server, s_ws_client_fd, &ws_frame);
if (ret_ws != ESP_OK) {
ESP_LOGW(TAG, "dropped");
// Failed to send, possibly socket busy or buffer full.
// Just ignore for now to keep ADC running.
// If it's a fatal socket error, we might want to invalidate fd,
// but async send usually returns QUEUE_FULL etc. for temp errors.
ESP_LOGW(TAG, "dropped: %s", esp_err_to_name(ret_ws));
// Invalidate FD if it's no longer valid (client disconnected)
if (ret_ws == ESP_ERR_INVALID_ARG || ret_ws == ESP_FAIL) {
s_ws_client_fd = -1;
}
}
}
}
@@ -193,14 +213,24 @@ static void adc_read_task(void *arg) {
}
}
static void continuous_adc_init(adc_channel_t *channel, uint8_t channel_num,
adc_continuous_handle_t *out_handle) {
uint32_t frame_size = get_optimal_buffer_size(s_sample_rate);
ESP_LOGI(TAG, "Dynamic Buffer Size: %lu bytes", frame_size);
adc_continuous_handle_cfg_t adc_config = {
.max_store_buf_size = 16384,
.conv_frame_size = ADC_READ_LEN,
.conv_frame_size = frame_size,
};
ESP_ERROR_CHECK(adc_continuous_new_handle(&adc_config, out_handle));
// Update the global read length used by the task (hacky but simple for now)
// Ideally return it, but our init function signature is fixed.
// We can rely on get_optimal_buffer_size(s_sample_rate) being consistent.
adc_continuous_config_t dig_cfg = {
.sample_freq_hz = s_sample_rate,
.conv_mode = ADC_CONV_MODE,