HC-SR04 using RMT - very fast

Deouss
Posts: 290
Joined: Tue Mar 20, 2018 11:36 am

HC-SR04 using RMT - very fast

Postby Deouss » Mon May 21, 2018 5:51 am

I was testing RMT and it turned out to be excellent tool )

Here is a code for ultrasonic sensor HC-SR04 using full hardware capabilities of ESP hardware Remote Control module


[code]
#include <stdio.h>
#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/queue.h"
#include "freertos/semphr.h"
#include "esp_err.h"
#include "esp_log.h"
#include "driver/rmt.h"
#include "driver/periph_ctrl.h"
#include "soc/rmt_reg.h"
#include <sys/time.h>
#include "driver/gpio.h"

#define RMT_TX_CHANNEL 1 /* RMT channel for transmitter */
#define RMT_TX_GPIO_NUM PIN_TRIGGER /* GPIO number for transmitter signal */
#define RMT_RX_CHANNEL 0 /* RMT channel for receiver */
#define RMT_RX_GPIO_NUM PIN_ECHO /* GPIO number for receiver */
#define RMT_CLK_DIV 100 /* RMT counter clock divider */
#define RMT_TX_CARRIER_EN 0 /* Disable carrier */
#define rmt_item32_tIMEOUT_US 9500 /*!< RMT receiver timeout value(us) */

#define RMT_TICK_10_US (80000000/RMT_CLK_DIV/100000) /* RMT counter value for 10 us.(Source clock is APB clock) */
#define ITEM_DURATION(d) ((d & 0x7fff)*10/RMT_TICK_10_US)

#define PIN_TRIGGER 18
#define PIN_ECHO 19

static void HCSR04_tx_init()
{
rmt_config_t rmt_tx;
rmt_tx.channel = RMT_TX_CHANNEL;
rmt_tx.gpio_num = RMT_TX_GPIO_NUM;
rmt_tx.mem_block_num = 1;
rmt_tx.clk_div = RMT_CLK_DIV;
rmt_tx.tx_config.loop_en = false;
rmt_tx.tx_config.carrier_duty_percent = 50;
rmt_tx.tx_config.carrier_freq_hz = 3000;
rmt_tx.tx_config.carrier_level = 1;
rmt_tx.tx_config.carrier_en = RMT_TX_CARRIER_EN;
rmt_tx.tx_config.idle_level = 0;
rmt_tx.tx_config.idle_output_en = true;
rmt_tx.rmt_mode = 0;
rmt_config(&rmt_tx);
rmt_driver_install(rmt_tx.channel, 0, 0);
}

static void HCSR04_rx_init()
{
rmt_config_t rmt_rx;
rmt_rx.channel = RMT_RX_CHANNEL;
rmt_rx.gpio_num = RMT_RX_GPIO_NUM;
rmt_rx.clk_div = RMT_CLK_DIV;
rmt_rx.mem_block_num = 1;
rmt_rx.rmt_mode = RMT_MODE_RX;
rmt_rx.rx_config.filter_en = true;
rmt_rx.rx_config.filter_ticks_thresh = 100;
rmt_rx.rx_config.idle_threshold = rmt_item32_tIMEOUT_US / 10 * (RMT_TICK_10_US);
rmt_config(&rmt_rx);
rmt_driver_install(rmt_rx.channel, 1000, 0);
}

void app_main()
{
HCSR04_tx_init();
HCSR04_rx_init();

rmt_item32_t item;
item.level0 = 1;
item.duration0 = RMT_TICK_10_US;
item.level1 = 0;
item.duration1 = RMT_TICK_10_US; // for one pulse this doesn't matter

size_t rx_size = 0;
RingbufHandle_t rb = NULL;
rmt_get_ringbuf_handle(RMT_RX_CHANNEL, &rb);
rmt_rx_start(RMT_RX_CHANNEL, 1);

double distance = 0;

for(;;)
{
rmt_write_items(RMT_TX_CHANNEL, &item, 1, true);
rmt_wait_tx_done(RMT_TX_CHANNEL, portMAX_DELAY);

rmt_item32_t* item = (rmt_item32_t*)xRingbufferReceive(rb, &rx_size, 1000);
distance = 340.29 * ITEM_DURATION(item->duration0) / (1000 * 1000 * 2); // distance in meters
printf("Distance is %f cm\n", distance * 100); // distance in centimeters

vRingbufferReturnItem(rb, (void*) item);
vTaskDelay(200 / portTICK_PERIOD_MS);
}

}
[/code]

BeWaterMyFriend
Posts: 1
Joined: Wed Oct 17, 2018 4:27 pm

Re: HC-SR04 using RMT - very fast

Postby BeWaterMyFriend » Wed Oct 17, 2018 4:31 pm

Great Example. Thanks for sharing !

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