ESP32 Peripheral Drivers built with ESP-IDF
This top-level driver collection provide high-level functions to operate the peripherals. If you are using ESP-IDF and cmake, clone it into the components directory of your project.
The MAX6675 is a SPI temperature sensor interface for K-type thermocouples. It measures from 0°C to 1023°C in 0.25°C increments. This driver can read and return Celsius, Fahrenheit and the raw data produced by the sensor.
The DHT22 is a temperature and humidity sensor that runs off 3V-5V and uses single-wire signaling to initiate and transmit its readings along with a checksum, with one reading being available up to one every two seconds.
This driver uses the ESP32 RMT device to capture the input from the DHT22. It uses a single RMT device and one RMT memory block only (i.e. it can use any one RMT device, even #7). By pulling the GPIO low this driver causes the DHT22 to signal a start pulse and following 40 data bits which are captured by the RMT and processed into five bytes. The start pulse is typically low 80µs + high 80µs, while each data bit pulse is low 50-70µs followed by a high of 25-30µs for 0 or a high of 70-80µs for 1.
The processed data status, the temperature (Celsius) and humidity (percent) can be read from the API, as can the raw 40 bit signal data. Looking for prior art for the RMT approach, jcollie's repo provided proof of concept.
The DS18B20 is a temperature sensor that uses the Dallas 1Wire bus for signaling and communication, and either runs off a 3V-5V supply or off power from the signaling wire parasistically. It measures from -55°C to +125°C and has selectable accuracy, from 9 to 12 bits. Multiple devices can run off the Dallas 1Wire bus as each is uniquely addressed. Upper and Lower temperature limits can be configured in each DS18B20 which if met will set the devices alarm state: A controller on the Dallas 1Wire bus can search the bus for devices with alarm states using an Alarm Search command, and without having to interogate each device on the bus.
#include <esp_system.h>
#include <freertos/FreeRTOS.h>
#include <freertos/task.h>
#include <math.h>
#include "MAX6675.h"
void app_main()
{
epd::MAX6675* max6675 = new epd::DS18B20(epd::MAX6675::SPI2);
while (true)
{
printf("temp R=%u\n", max6675->getRaw().temperature_reading);
printf("temp C=%f\n", max6675->getCelsius(false));
printf("temp F=%f\n", max6675->getFahrenheit(false));
vTaskDelay(20);
}
}ESP32-Peripheral-Drivers - Copyright 2019 technosf [http://github.com/technosf]
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