Seed the refresh gate with the interval it compares against

esphome/components/esp32_rmt_led_strip/led_strip.cpp

@@ -1,4 +1,5 @@
 #include "led_strip.h"
+#include <algorithm>
 #include <cinttypes>
 
 #ifdef USE_ESP32
@@ -14,6 +15,8 @@ namespace esphome::esp32_rmt_led_strip {
 ESPHOME_LOG_TAG(TAG, "esp32_rmt_led_strip");
 
 static const size_t RMT_SYMBOLS_PER_BYTE = 8;
+// Idle time the line must stay low between frames so the strip latches
+static const uint32_t RESET_GAP_US = 50;
 
 // Query the RMT default clock source frequency. This varies by variant:
 // APB (80MHz) on ESP32/S2/S3/C3, PLL_F80M (80MHz) on C6/P4, XTAL (32MHz) on H2.
@@ -91,10 +94,20 @@ void ESP32RMTLEDStripLightOutput::setup() {
   this->rmt_buf_ = rmt_allocator.allocate(buffer_size * 8 + 1);
 #endif
 
+  const uint32_t resolution_hz = rmt_resolution_hz();
+  // Longest wire time of one frame; write_state() defers instead of blocking until it has elapsed
+  uint32_t bit_ticks = std::max(this->params_.bit0.duration0 + this->params_.bit0.duration1,
+                                this->params_.bit1.duration0 + this->params_.bit1.duration1);
+  uint64_t frame_ticks = (uint64_t) bit_ticks * buffer_size * RMT_SYMBOLS_PER_BYTE + this->params_.reset.duration0 +
+                         this->params_.reset.duration1;
+  this->frame_time_us_ = frame_ticks * 1000000 / resolution_hz + RESET_GAP_US;
+  // Seed with the interval write_state() gates on, so the first frame is not deferred
+  this->last_refresh_ = micros() - std::max(this->frame_time_us_, this->max_refresh_rate_);
+
   rmt_tx_channel_config_t channel;
   memset(&channel, 0, sizeof(channel));
   channel.clk_src = RMT_CLK_SRC_DEFAULT;
-  channel.resolution_hz = rmt_resolution_hz();
+  channel.resolution_hz = resolution_hz;
   channel.gpio_num = gpio_num_t(this->pin_);
   channel.mem_block_symbols = this->rmt_symbols_;
   channel.trans_queue_depth = 1;
@@ -157,27 +170,16 @@ void ESP32RMTLEDStripLightOutput::set_led_params(uint32_t bit0_high, uint32_t bi
 }
 
 void ESP32RMTLEDStripLightOutput::write_state(light::LightState *state) {
-  // protect from refreshing too often
-  uint32_t now = micros();
-  auto rate = this->max_refresh_rate_.value_or(0);
-  if (rate != 0 && (now - this->last_refresh_) < rate) {
-    // try again next loop iteration, so that this change won't get lost
+  // Previous frame still on the wire, inside its reset gap, or refreshing too often:
+  // try again next loop iteration instead of blocking, so that this change won't get lost
+  if (micros() - this->last_refresh_ < std::max(this->frame_time_us_, this->max_refresh_rate_)) {
     this->schedule_show();
     return;
   }
-  this->last_refresh_ = now;
   this->mark_shown_();
 
   ESP_LOGVV(TAG, "Writing RGB values to bus");
 
-  esp_err_t error = rmt_tx_wait_all_done(this->channel_, 1000);
-  if (error != ESP_OK) {
-    ESP_LOGE(TAG, "RMT TX timeout");
-    this->status_set_warning();
-    return;
-  }
-  delayMicroseconds(50);
-
 #if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(5, 3, 0)
   memcpy(this->rmt_buf_, this->buf_, this->get_buffer_size_());
 #else
@@ -208,15 +210,20 @@ void ESP32RMTLEDStripLightOutput::write_state(light::LightState *state) {
   rmt_transmit_config_t config;
   memset(&config, 0, sizeof(config));
 #if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(5, 3, 0)
-  error = rmt_transmit(this->channel_, this->encoder_, this->rmt_buf_, this->get_buffer_size_(), &config);
+  esp_err_t error = rmt_transmit(this->channel_, this->encoder_, this->rmt_buf_, this->get_buffer_size_(), &config);
 #else
-  error = rmt_transmit(this->channel_, this->encoder_, this->rmt_buf_, len * sizeof(rmt_symbol_word_t), &config);
+  esp_err_t error =
+      rmt_transmit(this->channel_, this->encoder_, this->rmt_buf_, len * sizeof(rmt_symbol_word_t), &config);
 #endif
   if (error != ESP_OK) {
     ESP_LOGE(TAG, "RMT TX error");
     this->status_set_warning();
+    // retry next loop iteration so the frame is not lost
+    this->schedule_show();
     return;
   }
+  // Stamped after the transfer started so the gate above stays conservative
+  this->last_refresh_ = micros();
   this->status_clear_warning();
 }
 
@@ -242,7 +249,7 @@ void ESP32RMTLEDStripLightOutput::dump_config() {
                 "  Channel colors: %s\n"
                 "  Max refresh rate: %" PRIu32 "\n"
                 "  Number of LEDs: %u",
-                this->channel_colors_.to_string(channel_colors), this->max_refresh_rate_.value_or(0), this->num_leds_);
+                this->channel_colors_.to_string(channel_colors), this->max_refresh_rate_, this->num_leds_);
 }
 
 float ESP32RMTLEDStripLightOutput::get_setup_priority() const { return setup_priority::HARDWARE; }

esphome/components/esp32_rmt_led_strip/led_strip.h

@@ -86,7 +86,9 @@ class ESP32RMTLEDStripLightOutput final : public light::AddressableLight {
   light::ChannelColors channel_colors_{0, 1, 2, light::ChannelColors::NO_WHITE};
 
   uint32_t last_refresh_{0};
-  optional<uint32_t> max_refresh_rate_{};
+  uint32_t max_refresh_rate_{0};
+  // Worst-case wire time of one frame plus the reset gap, computed in setup()
+  uint32_t frame_time_us_{0};
 };
 
 }  // namespace esphome::esp32_rmt_led_strip