Pigpio issues

Targets Raspberry Pi
1

Just been playing with the pigpio module as wiringpi is no longer flavour of the month…

I have followed the code examples from Eugene’s book on setting up I2C.
Using the following code snippet:
pi = New pigpio
Call pi.gpioInitialise()
pi.Handle = pi.pigpio_start(nil, nil)
bus = 1

//init ADC1
ADCHandle = pi.i2c_open(bus, ADC1Address)
Listbox1.AddRow "MyHandle = " + ADCHandle.ToText
If ADCHandle < 0 then
Listbox1.AddRow "Error with address - use i2cdetect -y 1 to find it. Error: " + ADCHandle.ToString
End If
System.DebugLog "pi.handle: " + pi.Handle.ToString
System.DebugLog "ADChandle: " + ADCHandle.ToString

I always get 0 for pi.handle and ADCHandle, even if the ADC chip is not on the I2C bus.

I would assume that if the ADC chip is not on the bus, then when “ADCHandle = pi.i2c_open(bus, ADC1Address)” is run I should get an error, but the code carries on happily and reports 0.

Also having a bit of fun with i2c_write_device:
Data = pi.i2c_write_device(ADCHandle,buf, 3)
buf points to a memory block where I have 3 bytes to send. The count variable - should it be 2 (as in 0 to 2, that is 3 bytes), or 3 (as in 1 to 3)? Assuming the former - same as an array.

I had all of this working fine with the old wiringpi and GPIO module. I am trying to talk to an ADS1115 ADC.

I’m using a Pi Compute Module 4, latest OS.
All I2C devices are IDed when using suso i2cdetect -y 1

2

Solved it myself! Always good when that happens. :grinning:

The ADS1115 sends its 16 bit data back LSB first. I forgot about this.
In my old code, I was swapping the Bytes around, then presenting the result.
This is how to do it:

Var MyVal as UInt16 //Read conversation register (0)
MyVal = pi.i2c_read_word_data(ADC2Handle,0)
mb.UInt16Value(3) = MyVal
mb.LittleEndian = not mb.LittleEndian //Swap the bytes around
MyVal = mb.UInt16Value(3)
Listbox1.AddRow "ADC ch2 = " + Cstr(MyVal)

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