I don't have any MCP23S17 chips to test and debug them, however it would be nice to see what data are you sending to the chip. You can also disconnect SO pin from carambola2, attach a pullup resistor to it and measure it then (preferably with a new MCP23S17 chip).

Thank you Giedrius for the quick reply.

I am also concerned about this post

If the SPI is 2.5V, and the MCP23S17 is powered off 3.3v, the "Input High" volatge is specified as 0.8 VDD (0.8 x 3.3v = 2.64v). Is it possible that the MCP23S17 is not listening to my commands because the Carambola 2 SPI voltage is too low?

I have tried sending all sorts of commands listed in many "spidev" example which are mainly written for the Raspberry Pi and can confirm them with the logic analyzer as being sent, but still no response..



This is also a nice reference but on a completely different platform



These examples didn't work for me, it makes sense to me that you have setup the device first. So now I'm just doing:

0x40 0x0A 0x18 // write IOCON with 0x18
0x41 0x0A // read IOCON back

I will try Giedrius's test of disconnecting the MCP23S17's SO pin and pulling it high and anaylze it there.

I have changed VDD to 2.7V on the MCP23S17 and pulled SO high and probed again. No luck still no data output from the MCP23S17. There are a lot of variables here so this may be a bust for me.

Giedrius, You are developing the caramiot-dist package. Can you speak to some of the loew-level configuration involved? I do not want a python interface but I'm very interested in the lower-level configuration.

Well, the (software) SPI in caramiot is just a bitbanged GPIOs and that's really what there is to it.