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onewire_bus: using fixed mem_block_symbols for RMT RX (IEC-498) #702

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onewire_bus: using fixed mem_block_symbols for RMT RX (IEC-498) #702

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3a8fa46
Always use standard-sized mem_block_symbols, but read bytes one-by-on…
lukecyca Mar 12, 2026
1595e23
Read in chunks up to ONEWIRE_RMT_DEFAULT_MEM_BLOCK_SYMBOLS
lukecyca Mar 12, 2026
adff9eb
Address copilot code review
lukecyca Mar 13, 2026
7d40d6b
Merge branch 'master' into fixed-mem-block-symbols
lukecyca Mar 16, 2026
ad4ed31
Perform chunked reading conditionally, only on chips that do not supp…
lukecyca Mar 24, 2026
cacf9e0
Revert unintended change to onewire_bus/test_apps
lukecyca Mar 24, 2026
d717b99
Merge branch 'master' into fixed-mem-block-symbols
lukecyca Apr 2, 2026
4d18095
Merge branch 'master' into fixed-mem-block-symbols
lukecyca Apr 15, 2026
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65 changes: 47 additions & 18 deletions onewire_bus/src/onewire_bus_impl_rmt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,14 +30,6 @@ static const char *TAG = "1-wire.rmt";
#define ONEWIRE_RMT_DEFAULT_MEM_BLOCK_SYMBOLS 48
#endif

// for chips whose RMT RX channel doesn't support ping-pong, we need the user to tell the maximum number of bytes will be received
#if CONFIG_IDF_TARGET_ESP32 || CONFIG_IDF_TARGET_ESP32S2
// one RMT symbol represents one bit, so x8
#define ONEWIRE_RMT_RX_MEM_BLOCK_SIZE (rmt_config->max_rx_bytes * 8)
#else // otherwise, we just use one memory block, to save resources
#define ONEWIRE_RMT_RX_MEM_BLOCK_SIZE ONEWIRE_RMT_DEFAULT_MEM_BLOCK_SYMBOLS
#endif

/*
Reset Pulse:

Expand Down Expand Up @@ -229,10 +221,10 @@ static bool onewire_rmt_check_presence_pulse(rmt_symbol_word_t *rmt_symbols, siz
return ret;
}

static void onewire_rmt_decode_data(rmt_symbol_word_t *rmt_symbols, size_t symbol_num, uint8_t *rx_buf, size_t rx_buf_size)
static void onewire_rmt_decode_data(rmt_symbol_word_t *rmt_symbols, size_t symbol_num, uint8_t *rx_buf, size_t rx_buf_size, size_t start_bit)
{
size_t byte_pos = 0;
size_t bit_pos = 0;
size_t byte_pos = start_bit / 8;
size_t bit_pos = start_bit % 8;
for (size_t i = 0; i < symbol_num; i ++) {
if (rmt_symbols[i].duration0 > ONEWIRE_SLOT_BIT_SAMPLE_TIME) { // 0 bit
rx_buf[byte_pos] &= ~(1 << bit_pos); // LSB first
Expand Down Expand Up @@ -279,7 +271,7 @@ esp_err_t onewire_new_bus_rmt(const onewire_bus_config_t *bus_config, const onew
.clk_src = RMT_CLK_SRC_DEFAULT,
.resolution_hz = ONEWIRE_RMT_RESOLUTION_HZ,
.gpio_num = bus_config->bus_gpio_num,
.mem_block_symbols = ONEWIRE_RMT_RX_MEM_BLOCK_SIZE,
.mem_block_symbols = ONEWIRE_RMT_DEFAULT_MEM_BLOCK_SYMBOLS,
};
ESP_GOTO_ON_ERROR(rmt_new_rx_channel(&onewire_rx_channel_cfg, &bus_rmt->rx_channel),
err, TAG, "create rmt rx channel failed");
Expand Down Expand Up @@ -445,7 +437,7 @@ static esp_err_t onewire_bus_rmt_write_bytes(onewire_bus_handle_t bus, const uin
}

// While receiving data, we use rmt transmit channel to send 0xFF to generate read pulse,
// at the same time, receive channel is used to record weather the bus is pulled down by device.
// at the same time, receive channel is used to record whether the bus is pulled down by device.
static esp_err_t onewire_bus_rmt_read_bytes(onewire_bus_handle_t bus, uint8_t *rx_buf, size_t rx_buf_size)
{
onewire_bus_rmt_obj_t *bus_rmt = __containerof(bus, onewire_bus_rmt_obj_t, base);
Expand All @@ -455,20 +447,57 @@ static esp_err_t onewire_bus_rmt_read_bytes(onewire_bus_handle_t bus, uint8_t *r

xSemaphoreTake(bus_rmt->bus_mutex, portMAX_DELAY);

// transmit one bits to generate read clock
#if CONFIG_IDF_TARGET_ESP32 || CONFIG_IDF_TARGET_ESP32S2
// Read bytes in chunks up to the maximum hardware memory block size
// to improve efficiency while avoiding RMT RX overflow.
size_t max_bytes_per_chunk = ONEWIRE_RMT_DEFAULT_MEM_BLOCK_SYMBOLS / 8;
if (max_bytes_per_chunk == 0) max_bytes_per_chunk = 1;
if (max_bytes_per_chunk > rx_buf_size) max_bytes_per_chunk = rx_buf_size;

size_t bytes_read = 0;
while (bytes_read < rx_buf_size) {
size_t chunk_bytes = rx_buf_size - bytes_read;
if (chunk_bytes > max_bytes_per_chunk) {
chunk_bytes = max_bytes_per_chunk;
}

uint8_t tx_buffer[chunk_bytes];
memset(tx_buffer, 0xFF, chunk_bytes);

// receive chunk_bytes (chunk_bytes * 8 symbols)
ESP_GOTO_ON_ERROR(rmt_receive(bus_rmt->rx_channel, bus_rmt->rx_symbols_buf, chunk_bytes * 8 * sizeof(rmt_symbol_word_t), &onewire_rmt_rx_config),
err, TAG, "1-wire data receive failed");

// transmit chunk_bytes (chunk_bytes * 8 symbols) of all ones to generate read clock
ESP_GOTO_ON_ERROR(rmt_transmit(bus_rmt->tx_channel, bus_rmt->tx_bytes_encoder, tx_buffer, chunk_bytes, &onewire_rmt_tx_config),
err, TAG, "1-wire data transmit failed");

// wait for the transmission to finish and decode data
rmt_rx_done_event_data_t rmt_rx_evt_data;
ESP_GOTO_ON_FALSE(xQueueReceive(bus_rmt->receive_queue, &rmt_rx_evt_data, pdMS_TO_TICKS(1000)) == pdPASS, ESP_ERR_TIMEOUT,
err, TAG, "1-wire data receive timeout");
onewire_rmt_decode_data(rmt_rx_evt_data.received_symbols, rmt_rx_evt_data.num_symbols, rx_buf, rx_buf_size, bytes_read * 8);

bytes_read += chunk_bytes;
}
#else // CONFIG_IDF_TARGET_ESP32 || CONFIG_IDF_TARGET_ESP32S2
uint8_t tx_buffer[rx_buf_size];
memset(tx_buffer, 0xFF, rx_buf_size);
// transmit 1 bits while receiving

// receive rx_buf_size (rx_buf_size * 8 symbols)
ESP_GOTO_ON_ERROR(rmt_receive(bus_rmt->rx_channel, bus_rmt->rx_symbols_buf, rx_buf_size * 8 * sizeof(rmt_symbol_word_t), &onewire_rmt_rx_config),
err, TAG, "1-wire data receive failed");

// transmit rx_buf_size (rx_buf_size * 8 symbols) of all ones to generate read clock
ESP_GOTO_ON_ERROR(rmt_transmit(bus_rmt->tx_channel, bus_rmt->tx_bytes_encoder, tx_buffer, sizeof(tx_buffer), &onewire_rmt_tx_config),
err, TAG, "1-wire data transmit failed");

// wait the transmission finishes and decode data
// wait for the transmission to finish and decode data
rmt_rx_done_event_data_t rmt_rx_evt_data;
ESP_GOTO_ON_FALSE(xQueueReceive(bus_rmt->receive_queue, &rmt_rx_evt_data, pdMS_TO_TICKS(1000)) == pdPASS, ESP_ERR_TIMEOUT,
err, TAG, "1-wire data receive timeout");
onewire_rmt_decode_data(rmt_rx_evt_data.received_symbols, rmt_rx_evt_data.num_symbols, rx_buf, rx_buf_size);
onewire_rmt_decode_data(rmt_rx_evt_data.received_symbols, rmt_rx_evt_data.num_symbols, rx_buf, rx_buf_size, 0);
#endif // CONFIG_IDF_TARGET_ESP32 || CONFIG_IDF_TARGET_ESP32S2

err:
xSemaphoreGive(bus_rmt->bus_mutex);
Expand Down Expand Up @@ -512,7 +541,7 @@ static esp_err_t onewire_bus_rmt_read_bit(onewire_bus_handle_t bus, uint8_t *rx_
ESP_GOTO_ON_FALSE(xQueueReceive(bus_rmt->receive_queue, &rmt_rx_evt_data, pdMS_TO_TICKS(1000)) == pdPASS, ESP_ERR_TIMEOUT,
err, TAG, "1-wire bit receive timeout");
uint8_t rx_buffer = 0;
onewire_rmt_decode_data(rmt_rx_evt_data.received_symbols, rmt_rx_evt_data.num_symbols, &rx_buffer, sizeof(rx_buffer));
onewire_rmt_decode_data(rmt_rx_evt_data.received_symbols, rmt_rx_evt_data.num_symbols, &rx_buffer, sizeof(rx_buffer), 0);
*rx_bit = rx_buffer & 0x01;

err:
Expand Down