[hpsdr] FX2 / I2C multi-master

[Phil Harman]

Chris et al,

At the moment we are using the I2C capabilities of the FX2 chip to set up
the A/D and D/A converters plus an I/O expander. This is all provided as
part of the development tools that come with the Xylo board. At the moment
we can set up the A/D/A's then send digitised audio over the USB
bi-directionally and send commands to the I/O expander at the same time.

The I2C  operates over a separate pipe in the PC code to the A/D/A code. For
the time being this works fine and saves writing/borrowing other code.

I did look at adding an I2C master to the FPGA and sending the commands/data
via the USB - the number of LE's is not great and there is a open source I2C
core that is very well documented we could use (but see comments below).

The core will allow multiple masters on the same bus so no problems there.
Since I found that the Xylo code did what we needed initially I did not go
any further with an FPGA master.  Fame and glory awaits anyone who would
like to tackle this for the group - go for it Chris!

We will need to move away from the Xylo drivers in the not too distant
future (i.e. when we move to the Lionheart FPGA + USB board) and utilising
the great work and experience of the GNU project would be terrific.

In fact, even more  fame and glory is available to anyone who would like to
start porting this to the Xylo board since we are not going to be able to
use XyloUSB.inf and XyloUSB.sys with Lionheart.

73's Phil...VK6APH



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