PCF8574 Emulator

localroger

Here is something a little different I needed for a job at work. There are plenty of I2C objects floating around, including drivers for the PCF8574 8-bit parallel I/O expander. But I needed a propeller to pretend to be a PCF8574 to fake out another I2C host. This turned out to be a bit tricky, since the host ran at pretty high speed and Spin wasn't fast enough. I figured it might be useful to someone else since it provides the backbone for emulating any other I2C slave device.

I'd put it in the obex along with a couple of other things I have waiting, except that I still can't login or reset my password.

JonnyMac

I've been wanting to experiment with I2C slave code -- you just saved me some time. Thank you!

localroger

Glad to be of help JonnyMac, I was thinking someone else might be able to use it. If you're emulating anything other than a PCF8574 you can drop the code that sets the interrupt flag and replace it with a WAITPEQ or PNE.

Bill Henning

Very cool, and very useful!

I wonder how long before there are many little I2C device emulations embedded in it?

localroger wrote: »

Here is something a little different I needed for a job at work. There are plenty of I2C objects floating around, including drivers for the PCF8574 8-bit parallel I/O expander. But I needed a propeller to pretend to be a PCF8574 to fake out another I2C host. This turned out to be a bit tricky, since the host ran at pretty high speed and Spin wasn't fast enough. I figured it might be useful to someone else since it provides the backbone for emulating any other I2C slave device.

I'd put it in the obex along with a couple of other things I have waiting, except that I still can't login or reset my password.