From 33f3360a4b89c3d7c6d9bd4e4968987789c5593c Mon Sep 17 00:00:00 2001
From: Matt <bread@mailed.me.uk>
Date: Sat, 13 Dec 2025 11:21:09 +0000
Subject: [PATCH] Choose buffer size/count to maintain packet rate to WS client
 at different sample rates

---
 main/index.html | 26 +++++++++++++++-----------
 main/main.c     | 44 +++++++++++++++++++++++++++++++++++++-------
 2 files changed, 52 insertions(+), 18 deletions(-)

diff --git a/main/index.html b/main/index.html
index 96d37df..76d0a98 100644
--- a/main/index.html
+++ b/main/index.html
@@ -33,7 +33,7 @@
 
         .controls {
             display: grid;
-            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
+            grid-template-columns: repeat(auto-fit, minmax(8em, 1fr));
             gap: 15px;
         }
 
@@ -44,9 +44,13 @@
             color: #bbb;
         }
 
+        label {
+            width: 8em;
+        }
+
         input,
         select {
-            width: 80%;
+            width: 6em;
             padding: 8px;
             background: #3d3d3d;
             border: 1px solid #555;
@@ -108,11 +112,12 @@
         }
 
         #resetBtn {
-            background:#ef4444;
-            color:#fff;
-            padding:4px 8px;
-            font-size:0.8rem;
+            background: #222;
+            color: #e66;
+            border: 1px solid;
+            font-size: 0.8rem;
             height: 4em;
+            width: 6em;
         }
     </style>
 </head>
@@ -139,7 +144,7 @@
                     <label>Sample Rate (Hz)</label>
                     <input type="number" id="sampleRate" value="10000" min="1" max="83333">
                 </div>
-                <div>
+                <div style="display: none;">
                     <label>Bit Width</label>
                     <select id="bitWidth">
                         <option value="12" selected>12-bit</option>
@@ -157,14 +162,13 @@
                         <option value="3" selected>11 dB</option>
                     </select>
                 </div>
-                <div style="display: flex; align-items: center; gap: 10px;">
+                <div>
                     <div>
                         <label>Test Hz</label>
                         <input type="number" id="testHz" value="100" min="1" max="10000">
                     </div>
-                    <button id="resetBtn">Reset
-                    </button>
                 </div>
+                <button id="resetBtn">Reset</button>
             </form>
         </div>
 
@@ -174,4 +178,4 @@
     <script src="index.js"></script>
 </body>
 
-</html>
+</html>
\ No newline at end of file
diff --git a/main/main.c b/main/main.c
index 30ad2cd..5541f6b 100644
--- a/main/main.c
+++ b/main/main.c
@@ -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,