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fix(ESP32 RMT): size RMT memory block per chip, use DMA where available (fixes BLE/WiFi ghost pixels) #923

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fix(ESP32 RMT): size RMT memory block per chip, use DMA where available (fixes BLE/WiFi ghost pixels) #923

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15 changes: 10 additions & 5 deletions src/internal/methods/ESP/ESP32/NeoEsp32RmtXMethod.h
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Original file line number Diff line number Diff line change
Expand Up @@ -57,9 +57,6 @@ struct rmt_led_strip_encoder_t
rmt_symbol_word_t reset_code;
};

#define NEOPIXELBUS_RMT_INT_FLAGS (ESP_INTR_FLAG_LOWMED)


template<typename T_SPEED, typename T_INVERTED = NeoEsp32RmtNotInverted> class NeoEsp32RmtMethodBase
{
public:
Expand Down Expand Up @@ -101,11 +98,19 @@ template<typename T_SPEED, typename T_INVERTED = NeoEsp32RmtNotInverted> class N
rmt_tx_channel_config_t config = {};
config.clk_src = RMT_CLK_SRC_DEFAULT;
config.gpio_num = static_cast<gpio_num_t>(_pin);
config.mem_block_symbols = 192; // memory block size, 64 * 4 = 256 Bytes
#if SOC_RMT_SUPPORT_DMA
config.mem_block_symbols = 512; // DMA decouples the buffer from RMT memory, so this is just a sane DMA buffer size
#else
config.mem_block_symbols = SOC_RMT_TX_CANDIDATES_PER_GROUP * SOC_RMT_MEM_WORDS_PER_CHANNEL; // max symbols a single TX channel can borrow from all TX-capable channels in its group: 512 on original ESP32 (8x64), 96 on ESP32-C3 (2x48). Requesting more than this fails rmt_new_tx_channel with "no free tx channels" since there is no contiguous free memory to satisfy it. A bigger half-buffer gives the RMT ISR more slack against BLE-induced preemption before the WS2811/WS2812x 300 µs reset threshold is hit, so we ask for the most each chip can give.
#endif
config.resolution_hz = T_SPEED::RmtTicksPerSecond; // 1 MHz tick resolution, i.e., 1 tick = 1 µs
config.trans_queue_depth = 4; // set the number of transactions that can pend in the background
config.flags.invert_out = T_INVERTED::Inverted; // do not invert output signal
config.flags.with_dma = false; // do not need DMA backend
#if SOC_RMT_SUPPORT_DMA
config.flags.with_dma = true; // chips with small per-channel RMT memory (e.g. ESP32-S3: 48 words/channel) can't fit a large static block; DMA decouples the buffer from RMT memory and from ISR refill timing entirely
#else
config.flags.with_dma = false; // chips without DMA support (original ESP32, ESP32-C3) use the static block sized above
#endif

ret += rmt_new_tx_channel(&config, &_channel);
led_strip_encoder_config_t encoder_config = {};
Expand Down