208 lines
6.4 KiB
C
208 lines
6.4 KiB
C
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/* ****************************************************************************
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*
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* ESP32 platform interface for DHT temperature & humidity sensors
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*
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* Copyright (c) 2017, Arnim Laeuger
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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* ****************************************************************************/
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#include "platform.h"
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#include "platform_rmt.h"
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#include "driver/rmt.h"
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#include "driver/gpio.h"
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#include "freertos/FreeRTOS.h"
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#include "freertos/task.h"
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#include "esp_log.h"
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#undef DHT_DEBUG
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// RX idle threshold [us]
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// needs to be larger than any duration occurring during bit slots
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// datasheet specs up to 200us for "Bus master has released time"
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#define DHT_DURATION_RX_IDLE (250)
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// zero bit duration threshold [us]
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// a high phase
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// * shorter than this is detected as a zero bit
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// * longer than this is detected as a one bit
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#define DHT_DURATION_ZERO (50)
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// grouped information for RMT management
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static struct {
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int channel;
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RingbufHandle_t rb;
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int gpio;
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} dht_rmt = {-1, NULL, -1};
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static void dht_deinit( void )
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{
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// drive idle level 1
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gpio_set_level( dht_rmt.gpio, 1 );
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rmt_rx_stop( dht_rmt.channel );
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rmt_driver_uninstall( dht_rmt.channel );
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platform_rmt_release( dht_rmt.channel );
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// invalidate channel and gpio assignments
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dht_rmt.channel = -1;
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dht_rmt.gpio = -1;
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}
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static int dht_init( uint8_t gpio_num )
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{
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// acquire an RMT module for RX
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if ((dht_rmt.channel = platform_rmt_allocate( 1, RMT_MODE_RX )) >= 0) {
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#ifdef DHT_DEBUG
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ESP_LOGI("dht", "RMT RX channel: %d", dht_rmt.channel);
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#endif
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rmt_config_t rmt_rx;
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rmt_rx.channel = dht_rmt.channel;
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rmt_rx.gpio_num = gpio_num;
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rmt_rx.clk_div = 80; // base period is 1us
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rmt_rx.flags = 0;
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rmt_rx.mem_block_num = 1;
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rmt_rx.rmt_mode = RMT_MODE_RX;
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rmt_rx.rx_config.filter_en = true;
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rmt_rx.rx_config.filter_ticks_thresh = 30;
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rmt_rx.rx_config.idle_threshold = DHT_DURATION_RX_IDLE;
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if (rmt_config( &rmt_rx ) == ESP_OK) {
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if (rmt_driver_install( rmt_rx.channel, 512, PLATFORM_RMT_INTR_FLAGS ) == ESP_OK) {
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rmt_get_ringbuf_handle( dht_rmt.channel, &dht_rmt.rb );
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dht_rmt.gpio = gpio_num;
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// use gpio for TX direction
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// drive idle level 1
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gpio_set_level( gpio_num, 1 );
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gpio_pullup_dis( gpio_num );
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gpio_pulldown_dis( gpio_num );
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gpio_set_direction( gpio_num, GPIO_MODE_INPUT_OUTPUT_OD );
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gpio_set_intr_type( gpio_num, GPIO_INTR_DISABLE );
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return PLATFORM_OK;
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}
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}
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platform_rmt_release( dht_rmt.channel );
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}
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return PLATFORM_ERR;
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}
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int platform_dht_read( uint8_t gpio_num, uint8_t wakeup_ms, uint8_t *data )
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{
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if (dht_init( gpio_num ) != PLATFORM_OK)
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return PLATFORM_ERR;
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// send start signal and arm RX channel
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TickType_t xDelay = pdMS_TO_TICKS( wakeup_ms ) > 0 ? pdMS_TO_TICKS( wakeup_ms ) : 1;
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gpio_set_level( gpio_num, 0 ); // pull wire low
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vTaskDelay( xDelay ); // time low phase
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rmt_rx_start( dht_rmt.channel, true ); // arm RX channel
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gpio_set_level( gpio_num, 1 ); // release wire
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// wait for incoming bit stream
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size_t rx_size;
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rmt_item32_t* rx_items = (rmt_item32_t *)xRingbufferReceive( dht_rmt.rb, &rx_size, pdMS_TO_TICKS( 100 ) );
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// default is "no error"
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// error conditions have to overwrite this with PLATFORM_ERR
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int res = PLATFORM_OK;
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if (rx_items) {
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#ifdef DHT_DEBUG
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ESP_LOGI("dht", "rx_items received: %d", rx_size);
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for (size_t i = 0; i < rx_size / 4; i++) {
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ESP_LOGI("dht", "level: %d, duration %d", rx_items[i].level0, rx_items[i].duration0);
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ESP_LOGI("dht", "level: %d, duration %d", rx_items[i].level1, rx_items[i].duration1);
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}
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#endif
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// we expect 40 bits of payload plus a response bit and two edges for start and stop signals
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// each bit on the wire consumes 2 rmt samples (and 2 rmt samples stretch over 4 bytes)
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if (rx_size >= (5*8 + 1+1) * 4) {
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// check framing
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if (rx_items[ 0].level0 == 1 && // rising edge of the start signal
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rx_items[ 0].level1 == 0 && rx_items[1].level0 == 1 && // response signal
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rx_items[41].level1 == 0) { // falling edge of stop signal
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// run through the bytes
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for (size_t byte = 0; byte < 5 && res == PLATFORM_OK; byte++) {
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size_t bit_pos = 1 + byte*8;
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data[byte] = 0;
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// decode the bits inside a byte
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for (size_t bit = 0; bit < 8; bit++, bit_pos++) {
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if (rx_items[bit_pos].level1 != 0) {
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// not a falling edge, terminate decoding
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res = PLATFORM_ERR;
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break;
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}
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// ignore duration of low level
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// data is sent MSB first
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data[byte] <<= 1;
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if (rx_items[bit_pos + 1].level0 == 1 && rx_items[bit_pos + 1].duration0 > DHT_DURATION_ZERO)
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data[byte] |= 1;
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}
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#ifdef DHT_DEBUG
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ESP_LOGI("dht", "data 0x%02x", data[byte]);
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#endif
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}
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// all done
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} else {
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// framing mismatch on start, response, or stop signals
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res = PLATFORM_ERR;
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}
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} else {
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// too few bits received
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res = PLATFORM_ERR;
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}
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vRingbufferReturnItem( dht_rmt.rb, (void *)rx_items );
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} else {
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// time out occurred, this indicates an unconnected / misconfigured bus
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res = PLATFORM_ERR;
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}
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dht_deinit();
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return res;
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}
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