Holidays this week and a sudden bust of summer so not much done in the shack.
Since my student finishes next week I needed to let her have the hardware as well so only did simulations. Current status is that I have a working "simulation" of a full duplex sound system over the USB. The single bit PWM D/A converter works well and is very simple to code.
My student has her Wolfson A/D to USB to PortAudio fully working (written in VHDL) and has full stereo audio playing, sample graphs look good and audio sounds fine.
In order to help with the inevitable debugging of the full duplex audio I decided to add an RS232 port to the Xylo. That way we can send debug data to the serial port of a PC to help the coding process.
I found that I didn't have to write any Verilog code to do this since there is a very nice RS232 Tx/Rx example that comes with the Xylo board ( see \Projects\SerialRxTx). Not only that but if you hit 'Control T' when the FPGAconf program is running then up pops a full duplex terminal program. This seems to run from COM1 at 115kb. I made up a RS232 to 5v converter using a MAX232 chip and connected it to the secondary connector ( the one next to the I2C) on the Xylo. Try compiling and running the code - any key you send from the PC comes back with one added e.g. send 'A' and 'B' comes back etc.
I'll add RS232 to my full duplex code and then start the debug process! And just to set the record straight - I had a bug in my Verilog code and one in my C code, they cancelled each other out and was the reason I was getting nice audio from PortAudio. Perhaps a case of 'two wrongs actually making a right"!
73's Phil... VK6APH
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