Grafting PCF8574A onto SR V9, for external filter switching.
Getting back into this after a long while away.
I'm working (still) to use the SR V9 RX with Faros/Omnirig for multi band HF beacon monitoring. I have the basic control of the Si570 working, so the RX does work OK, but, it get's hammered at night here in the UK with large out of band signals that produce all sorts of crud that causes Faros to misidentify things, a filter is needed.
To that end, I've built one of the G6LBQ 9 band filters.
The 5 bands of interst so far have tuned up nicely arround the 5 spot frequencies, but I need to switch them in/out of circuit as needed.
Don't worry about developing the diode switch drive signals, that's easy peasy. What's got me going in circles, is trying to get control of a Philips PCF8574A, grafted onto the i2c bus from the AtTiny85.
The chip is a good'un (came out of a working Velman K8000 external I/O kit) but though I still have full control of the Si570, the faded grey cell can't figure its way through the maze of uncommented and inapropriately named variables in the source code for the Si570 USB Test program, at this low level.
I've successfully added a Com port driver, and extra code to take a "tune" command and parameter from Omnirig via com0com, do the nesesary (+or- IF Offset, then multiply by 4) fill in the appropriate dialog, and hit the button to send the result to the Si570, that works well with the help of com0com. So I now have control of the Si570 itself from Faros/Omnirig, that was fairly easy!
As I think others have been here before, what does one need to send to the AtTiny85, just to communicate with the PCF8574A?
I just need to send a byte to the port, and maybe read one back at some point. (I have the data sheet for the PCF8574A.) Again, I'll handle what bit pattern to send and when, I just need a route to that chip.
The info I'm lacking I think, is exactly how the AtTiny85 firmware interacts with the code in the Si7570 USNB test program, I don't do C very well (but I was happy in Delphi.) In any case, what little I've seen of that code (unable to locate an example just now) it's even more inscrutable than that in the Si570 USB test program!
Hints and pointers welcome. Please....