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