Fastrack I2C for PCF8574A

[awneil]

Cross-posted from wavecom.com/modules/movie/sc … =5279#5279

@I

I am trying to use the Fastrack’s GPIO4&5 as a soft I2C bus to talk to a PCF8574A IO expander.

With no I2C device attached, adl_busSubscribe returns 0, and adl_busRead and adl_busWrite both return -31; ie, WM_BUS_NOT_CONNECTED_ON_I2C - which makes sense!

When I first attached my PCF8574A, with no pullups, I still got WM_BUS_NOT_CONNECTED_ON_I2C.
(the use of pullups is undocumented - see wavecom.com/modules/movie/sc … =4535#4535 )

So I added 1k pullups (to 3V), and now adl_busRead and adl_busWrite both return -1; ie, WM_BUS_MODE_UNKNOWN_TYPE - what does this indicate?

Using AT+WBR just returns “ERROR” - is there any way to get additional error details from this command?