78 lines
3.1 KiB
C
78 lines
3.1 KiB
C
/* ds18b20_onewire.c - Retrieves readings from one or more DS18B20 temperature
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* sensors, and prints the results to stdout.
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*
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* This sample code is in the public domain.,
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*/
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#include "FreeRTOS.h"
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#include "task.h"
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#include "esp/uart.h"
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#include "ds18b20/ds18b20.h"
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#define SENSOR_GPIO 13
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#define MAX_SENSORS 8
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#define RESCAN_INTERVAL 8
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#define LOOP_DELAY_MS 250
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void print_temperature(void *pvParameters) {
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ds18b20_addr_t addrs[MAX_SENSORS];
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float temps[MAX_SENSORS];
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int sensor_count;
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// There is no special initialization required before using the ds18b20
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// routines. However, we make sure that the internal pull-up resistor is
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// enabled on the GPIO pin so that one can connect up a sensor without
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// needing an external pull-up (Note: The internal (~47k) pull-ups of the
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// ESP8266 do appear to work, at least for simple setups (one or two sensors
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// connected with short leads), but do not technically meet the pull-up
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// requirements from the DS18B20 datasheet and may not always be reliable.
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// For a real application, a proper 4.7k external pull-up resistor is
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// recommended instead!)
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gpio_set_pullup(SENSOR_GPIO, true, true);
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while(1) {
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// Every RESCAN_INTERVAL samples, check to see if the sensors connected
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// to our bus have changed.
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sensor_count = ds18b20_scan_devices(SENSOR_GPIO, addrs, MAX_SENSORS);
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if (sensor_count < 1) {
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printf("\nNo sensors detected!\n");
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} else {
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printf("\n%d sensors detected:\n", sensor_count);
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// If there were more sensors found than we have space to handle,
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// just report the first MAX_SENSORS..
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if (sensor_count > MAX_SENSORS) sensor_count = MAX_SENSORS;
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// Do a number of temperature samples, and print the results.
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for (int i = 0; i < RESCAN_INTERVAL; i++) {
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ds18b20_measure_and_read_multi(SENSOR_GPIO, addrs, sensor_count, temps);
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for (int j = 0; j < sensor_count; j++) {
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// The DS18B20 address is a 64-bit integer, but newlib-nano
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// printf does not support printing 64-bit values, so we
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// split it up into two 32-bit integers and print them
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// back-to-back to make it look like one big hex number.
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uint32_t addr0 = addrs[j] >> 32;
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uint32_t addr1 = addrs[j];
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float temp_c = temps[j];
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float temp_f = (temp_c * 1.8) + 32;
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printf(" Sensor %08x%08x reports %f deg C (%f deg F)\n", addr0, addr1, temp_c, temp_f);
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}
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printf("\n");
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// Wait for a little bit between each sample (note that the
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// ds18b20_measure_and_read_multi operation already takes at
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// least 750ms to run, so this is on top of that delay).
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vTaskDelay(LOOP_DELAY_MS / portTICK_RATE_MS);
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}
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}
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}
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}
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void user_init(void) {
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uart_set_baud(0, 115200);
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xTaskCreate(&print_temperature, "print_temperature", 256, NULL, 2, NULL);
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}
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