yryz / ds18b20

Golang get temperature from ds18b20 sensor connected to a Raspberry PI (GPIO w1 pin).

ds18b20

Get sensor data from ds18b20 connected to the Raspberry (GPIO w1 pin).

Usage

Connect DS18B20

On the Raspberry Pi, you will need to add dtoverlay=w1-gpio" (for regular connection) or dtoverlay=w1-gpio,pullup="y" (for parasitic connection) to your /boot/config.txt. The default data pin is GPIO4 (RaspPi connector pin 7), but that can be changed from 4 to x with dtoverlay=w1-gpio,gpiopin=x.

Here's what I did:

sudo echo dtoverlay=w1-gpio-pullup,gpiopin=4 >> /boot/config.txt
sudo modprobe w1_gpio && sudo modprobe w1_therm

Drivers

1-Wire drivers need to be loaded in order to create the connection between the physical sensor and the rPI. You can load them from the terminal (or from the bin/modules.sh script).

sudo modprobe wire
sudo modprobe w1-gpio
sudo modprobe w1-therm

Install

go get github.com/yryz/ds18b20

Code

package main

import (
    "fmt"

    "github.com/yryz/ds18b20"
)

func main() {
    sensors, err := ds18b20.Sensors()
    if err != nil {
        panic(err)
    }

    fmt.Printf("sensor IDs: %v\n", sensors)

    for _, sensor := range sensors {
        t, err := ds18b20.Temperature(sensor)
        if err == nil {
            fmt.Printf("sensor: %s temperature: %.2f°C\n", sensor, t)
        }
    }
}

ds18b20's Issues

Result for case 'f'?

With all due respect, while I agree (FWIW) with the code in case '0', I question case 'f'.
To try to help, the 2 hex strings (data) I get back from 2 DSs are:
dd ff 4b 46 7f ff 03 10 25 : crc=25 YES
16 00 4b 46 7f ff 0a 10 a5 : crc=a5 YES
The temp is hovering around 0C and have used several DSs, all of which provide reasonably accurate results once the temps rise above about .5 thru 1.5C (w/in variances and compared against other HTU21D and AM2315 probes, as well as WeatherUnderground).

Validate temperature data on read

Summary:
This library does not validate that a correct temperature was obtained. Note this is only to validate that the 1Wire communication was successful; the DS18b20 sensor does not have self-test.

Observed behavior:
The first line of the w1 "file" is a CRC validation of the temperature value.
At this moment, the yryz/ds18b20 library does not validate that the CRC is valid before returning a temperature reading.

Desired behavior:
Expect the CRC tag to be present and "YES" immediately after.
Should this condition fail, return an error.