Adafruit STEMMA Soil Sensor driver

[FaithRaven]

I wonder if it's possible to use the Adafruit STEMMA Soil Sensor with an ESP32 board running MicroPython.

Any tips to steer me in the right direction will be greatly appreciated.

[MostlyHarmless]

Possible for sure, it is just another I2C device.

I would start by connecting it and then using machine.I2C's scan() method. That should reveal the device's I2C address.

A quick Google search told me that the thing produces a "moisture level" value between 200 and 2000. That value can be found at memory address 0x10, representing touch pin 1. There is also a temperature sensor. My guess is that the reading of that can be found in Celsius at some other memory location.

You should not be able to damage an I2C device by reading from it. So unless you can find a datasheet, start poking around.


Regards, Jan

[pythoncoder]

Adafruit have a CircuitPython driver for it here. I've only glanced at it but it seems rather heavyweight.

[FaithRaven]

Thank you both for steering me in the right direction. I've managed to strip Adafruit's drivers down to the essentials and this is what works for me:

I've published the code and usage instructions at https://github.com/mihai-dinculescu/mic ... ter/seesaw.

[pythoncoder]

Well done! I've ported drivers from CircuitPython to MicroPython. Adafruit's approach to coding prioritises ease of use by beginners over performance and code complexity. The upshot is that porting drivers from CircuitPython can be tougher than porting them from C.

[dhust]

Thank you both for steering me in the right direction. I've managed to strip Adafruit's drivers down to the essentials and this is what works for me:

I've published the code and usage instructions at https://github.com/mihai-dinculescu/mic ... ter/seesaw.

Couldn't get this to work. Not sure what's wrong. Using a Wemos D1 Mini.
Here is my code:

Code: Select all

import stemma_soil_sensor

SDA_PIN = 4 # update this
SCL_PIN = 5 # update this

i2c = machine.I2C(sda=machine.Pin(SDA_PIN), scl=machine.Pin(SCL_PIN), freq=400000)
seesaw = stemma_soil_sensor.StemmaSoilSensor(i2c)

# get moisture
moisture = seesaw.get_moisture()

# get temperature
temperature = seesaw.get_temp()

Here is my error:

ampy.pyboard.PyboardError: ('exception', b'', b'Traceback (most recent call last):\r\n File "<stdin>", line 47, in <module>\r\n File "stemma_soil_sensor.py", line 62, in __init__\r\n File "seesaw.py", line 64, in __init__\r\n File "seesaw.py", line 68, in sw_reset\r\n File "seesaw.py", line 79, in _write8\r\n File "seesaw.py", line 98, in _write\r\nOSError: [Errno 110] ETIMEDOUT\r\n')

Thoughts on how to fix this or what I'm missing?

[marcidy]

That probably means the i2c bus can't find the sensor.

can you see your devices when scanning the i2c bus on the repl?

[dhust]

It looks like you are correct. Here is what I ran and the results

Code: Select all

import machine

i2c = machine.I2C(scl=machine.Pin(5), sda=machine.Pin(4))
print('Scan i2c bus...')
devices = i2c.scan()
print(devices)

if len(devices) == 0:
  print("No i2c device !")
else:
  print('i2c devices found:',len(devices))

  for device in devices:  
    print("Decimal address: ",device," | Hexa address: ",hex(device))

Code: Select all

Scan i2c bus...
[]
No i2c device !

What does that mean? What are some next steps?

[marcidy]

you need to check the connections and make sure they correspond correctly to the pin declarations. is sda connected to sda? is that pin declared as sda in the code? etc.

post the schematic you are using and confirm you have connected everything according to the schematic

if the connection is correct, it's possible the sensor is broken, and so test with another sensor.

[dhust]

you need to check the connections and make sure they correspond correctly to the pin declarations. is sda connected to sda? is that pin declared as sda in the code? etc.

post the schematic you are using and confirm you have connected everything according to the schematic

if the connection is correct, it's possible the sensor is broken, and so test with another sensor.

That's unfortunate. I've checked the connections a few times. It's good there. There are no schematics to post. I just connected ground to ground, vin to 5V or 3.3V, SDA to D2 (GPIO4: SDA), and SCL to D1 (GPIO5: SCL). I'll have to swap out the ESP8266 later to see if that's the issue. Shouldn't be because it's brand new but we'll see.