I might have a faulty SHT25

Hardware
1

I’ve plugged the MCP23008 , ADC121C021, and SHT25 into my Pi2 via the i2c-shield.

Google Photos

The MCP23008 is powered by it’s power adaptor.

The red power lights for each device comes on.

and on my Pi2 i have rasbian with node-red installed, the I2C communications have been enabled via the raspi-config

However with the following node-red flow to report the discovered I2C devices addresses :

[{“id”:“7a2e4ed3.4bba1”,“type”:“tab”,“label”:“Flow 1”,“disabled”:false,“info”:""},{“id”:“373d2416.edca24”,“type”:“inject”,“z”:“7a2e4ed3.4bba1”,“name”:"",“topic”:"",“payload”:"",“payloadType”:“date”,“repeat”:"",“crontab”:"",“once”:false,“onceDelay”:0.1,“x”:100,“y”:220,“wires”:[[“f3c122a1.aaa9a8”]]},{“id”:“556dd833.88f618”,“type”:“debug”,“z”:“7a2e4ed3.4bba1”,“name”:"",“active”:true,“tosidebar”:true,“console”:false,“tostatus”:false,“complete”:“false”,“x”:190,“y”:340,“wires”:[]},{“id”:“f3c122a1.aaa9a8”,“type”:“i2c scan”,“z”:“7a2e4ed3.4bba1”,“x”:140,“y”:280,“wires”:[[“556dd833.88f618”],[“556dd833.88f618”]]}]

This is the flow without the SHT25 attached:
https://i.imgur.com/NBUWhmZ.gifv

This is the same flow, with the SHT25 attached:
https://i.imgur.com/2JMOqih.gifv

Shouldn’t I expect to see the address 40 in that list ?

2

Running a few things on the ssh terminal:

pi@red:~ $ ls /dev/*i2c*
/dev/i2c-1  /dev/i2c-3

pi@red:~ $ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: 20 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: 40 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

So it seems all my i2c devices are there and responding… but differently inside node-red.

./confused

3

Looks like hardware is connected correctly and responding to the i2c scan command. You might look into your node red setup.
@Trey Might have node red lib for sht25?

4

Its possible that Node Red is using a general call to request everything check in and the SHT25 doesn’t respond whereas the in the command line it runs through every channel specifically.

5

Yeah definitely something to do with node-red.

i tried the python script here out: https://github.com/ControlEverythingCommunity/SHT25

Works fine.

Now i just need to get it working in node-red

6

Good news:

installed the 12c node package and created a function node with:

const i2c = global.get('i2c');

const deviceAddress = 0x40;
const temperatureCommand = 0xF3;
const humidityCommand = 0xF5;

const wire = new i2c(deviceAddress, {device: '/dev/i2c-1'}); // point to your i2c address, debug provides REPL interface


function getTemperature () {
    return new Promise((resolve, reject) => {
        wire.writeByte(temperatureCommand, () => {
            setTimeout(() => {
                wire.read(2, function(err, response) {
                    const [msb, lsb] = response;
                    const temp = (msb * 256 + lsb);
                    resolve(-46.85 + ((temp * 175.72) / 65536.0))
                });
          }, 500);
        })
    });
}

function getHumidity () {
    return new Promise((resolve) => {
        resolve();
    })
}


Promise.all([
    getTemperature(),
    getHumidity()
])
    .then(([temperature, humidity]) => {
       node.send({
           payload: {temperature, humidity}
       });
    });
   
return;

Is getting me temperature readings!

7

Nice! Glad you got it working and thanks for sharing your code.