Skip to content

Commit

Permalink
esp32/machine_bitstream: Replace bit-bang code with RMT-based driver.
Browse files Browse the repository at this point in the history 
This aims to solve glitching issues on long neopixel strips.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>
  • Loading branch information
@jimmo @dpgeorge
jimmo authored and dpgeorge committed Dec 22, 2021
1 parent 09fe80d commit 599b61c
Show file tree
Hide file tree
Showing 3 changed files with 104 additions and 43 deletions.
6 changes: 6 additions & 0 deletions ports/esp32/esp32_rmt.c
View file
Expand Up @@ -29,6 +29,8 @@
#include "mphalport.h"
#include "driver/rmt.h"

#include "modesp32.h"

// This exposes the ESP32's RMT module to MicroPython. RMT is provided by the Espressif ESP-IDF:
//
// https://docs.espressif.com/projects/esp-idf/en/latest/api-reference/peripherals/rmt.html
Expand Down Expand Up @@ -73,6 +75,10 @@ STATIC mp_obj_t esp32_rmt_make_new(const mp_obj_type_t *type, size_t n_args, siz
mp_uint_t idle_level = args[3].u_bool;
mp_obj_t tx_carrier_obj = args[4].u_obj;

if (channel_id == MICROPY_HW_ESP32_RMT_CHANNEL_BITSTREAM) {
mp_raise_ValueError(MP_ERROR_TEXT("reserved channel id"));
}

if (clock_div < 1 || clock_div > 255) {
mp_raise_ValueError(MP_ERROR_TEXT("clock_div must be between 1 and 255"));
}
Expand Down
138 changes: 95 additions & 43 deletions ports/esp32/machine_bitstream.c
View file
Expand Up @@ -24,63 +24,115 @@
* THE SOFTWARE.
*/

// This is a translation of the cycle counter implementation in ports/stm32/machine_bitstream.c.

#include "py/mpconfig.h"
#include "py/mphal.h"

#if MICROPY_PY_MACHINE_BITSTREAM

#define NS_TICKS_OVERHEAD (6)
#include "driver/rmt.h"

void IRAM_ATTR machine_bitstream_high_low(mp_hal_pin_obj_t pin, uint32_t *timing_ns, const uint8_t *buf, size_t len) {
uint32_t pin_mask, gpio_reg_set, gpio_reg_clear;
#if !CONFIG_IDF_TARGET_ESP32C3
if (pin >= 32) {
pin_mask = 1 << (pin - 32);
gpio_reg_set = GPIO_OUT1_W1TS_REG;
gpio_reg_clear = GPIO_OUT1_W1TC_REG;
} else
#endif
{
pin_mask = 1 << pin;
gpio_reg_set = GPIO_OUT_W1TS_REG;
gpio_reg_clear = GPIO_OUT_W1TC_REG;
}
#include "modesp32.h"

// Convert ns to cpu ticks [high_time_0, period_0, high_time_1, period_1].
uint32_t fcpu_mhz = ets_get_cpu_frequency();
for (size_t i = 0; i < 4; ++i) {
timing_ns[i] = fcpu_mhz * timing_ns[i] / 1000;
if (timing_ns[i] > NS_TICKS_OVERHEAD) {
timing_ns[i] -= NS_TICKS_OVERHEAD;
}
if (i % 2 == 1) {
// Convert low_time to period (i.e. add high_time).
timing_ns[i] += timing_ns[i - 1];
}
#if ESP_IDF_VERSION < ESP_IDF_VERSION_VAL(4, 1, 0)
// This convenience macro was not available in earlier IDF versions.
#define RMT_DEFAULT_CONFIG_TX(gpio, channel_id) \
{ \
.rmt_mode = RMT_MODE_TX, \
.channel = channel_id, \
.clk_div = 80, \
.gpio_num = gpio, \
.mem_block_num = 1, \
.tx_config = { \
.loop_en = false, \
.carrier_freq_hz = 38000, \
.carrier_duty_percent = 33, \
.carrier_level = RMT_CARRIER_LEVEL_HIGH, \
.carrier_en = false, \
.idle_level = RMT_IDLE_LEVEL_LOW, \
.idle_output_en = true, \
} \
}
#endif

uint32_t irq_state = mp_hal_quiet_timing_enter();
// Logical 0 and 1 values (encoded as a rmt_item32_t).
// The duration fields will be set later.
STATIC rmt_item32_t bitstream_high_low_0 = {{{ 0, 1, 0, 0 }}};
STATIC rmt_item32_t bitstream_high_low_1 = {{{ 0, 1, 0, 0 }}};

for (size_t i = 0; i < len; ++i) {
uint8_t b = buf[i];
for (size_t j = 0; j < 8; ++j) {
GPIO_REG_WRITE(gpio_reg_set, pin_mask);
uint32_t start_ticks = mp_hal_ticks_cpu();
uint32_t *t = &timing_ns[b >> 6 & 2];
while (mp_hal_ticks_cpu() - start_ticks < t[0]) {
;
}
GPIO_REG_WRITE(gpio_reg_clear, pin_mask);
b <<= 1;
while (mp_hal_ticks_cpu() - start_ticks < t[1]) {
;
// See https://github.com/espressif/esp-idf/blob/master/examples/common_components/led_strip/led_strip_rmt_ws2812.c
// This is called automatically by the IDF during rmt_write_sample in order to
// convert the byte stream to rmt_item32_t's.
STATIC void IRAM_ATTR bitstream_high_low_rmt_adapter(const void *src, rmt_item32_t *dest, size_t src_size, size_t wanted_num, size_t *translated_size, size_t *item_num) {
if (src == NULL || dest == NULL) {
*translated_size = 0;
*item_num = 0;
return;
}

size_t size = 0;
size_t num = 0;
uint8_t *psrc = (uint8_t *)src;
rmt_item32_t *pdest = dest;
while (size < src_size && num < wanted_num) {
for (int i = 0; i < 8; i++) {
// MSB first
if (*psrc & (1 << (7 - i))) {
pdest->val = bitstream_high_low_1.val;
} else {
pdest->val = bitstream_high_low_0.val;
}
num++;
pdest++;
}
size++;
psrc++;
}

mp_hal_quiet_timing_exit(irq_state);
*translated_size = size;
*item_num = num;
}

// Use the reserved RMT channel to stream high/low data on the specified pin.
void machine_bitstream_high_low(mp_hal_pin_obj_t pin, uint32_t *timing_ns, const uint8_t *buf, size_t len) {
rmt_config_t config = RMT_DEFAULT_CONFIG_TX(pin, MICROPY_HW_ESP32_RMT_CHANNEL_BITSTREAM);

// Use 40MHz clock (although 2MHz would probably be sufficient).
config.clk_div = 2;

// Install the driver on this channel & pin.
check_esp_err(rmt_config(&config));
check_esp_err(rmt_driver_install(config.channel, 0, 0));

// Get the tick rate in kHz (this will likely be 40000).
uint32_t counter_clk_khz = 0;
#if ESP_IDF_VERSION < ESP_IDF_VERSION_VAL(4, 1, 0)
uint8_t div_cnt;
check_esp_err(rmt_get_clk_div(config.channel, &div_cnt));
counter_clk_khz = APB_CLK_FREQ / div_cnt;
#else
check_esp_err(rmt_get_counter_clock(config.channel, &counter_clk_khz));
#endif

counter_clk_khz /= 1000;

// Convert nanoseconds to pulse duration.
bitstream_high_low_0.duration0 = (counter_clk_khz * timing_ns[0]) / 1e6;
bitstream_high_low_0.duration1 = (counter_clk_khz * timing_ns[1]) / 1e6;
bitstream_high_low_1.duration0 = (counter_clk_khz * timing_ns[2]) / 1e6;
bitstream_high_low_1.duration1 = (counter_clk_khz * timing_ns[3]) / 1e6;

// Install the bits->highlow translator.
rmt_translator_init(config.channel, bitstream_high_low_rmt_adapter);

// Stream the byte data using the translator.
check_esp_err(rmt_write_sample(config.channel, buf, len, true));

// Wait 50% longer than we expect (if every bit takes the maximum time).
uint32_t timeout_ms = (3 * len / 2) * (1 + (8 * MAX(timing_ns[0] + timing_ns[1], timing_ns[2] + timing_ns[3])) / 1000);
check_esp_err(rmt_wait_tx_done(config.channel, pdMS_TO_TICKS(timeout_ms)));

// Uninstall the driver.
check_esp_err(rmt_driver_uninstall(config.channel));
}

#endif // MICROPY_PY_MACHINE_BITSTREAM
3 changes: 3 additions & 0 deletions ports/esp32/modesp32.h
View file
Expand Up @@ -31,4 +31,7 @@ extern const mp_obj_type_t esp32_partition_type;
extern const mp_obj_type_t esp32_rmt_type;
extern const mp_obj_type_t esp32_ulp_type;

// Reserve the last channel for machine.bitstream.
#define MICROPY_HW_ESP32_RMT_CHANNEL_BITSTREAM (RMT_CHANNEL_MAX - 1)

#endif // MICROPY_INCLUDED_ESP32_MODESP32_H

0 comments on commit 599b61c

Please sign in to comment.