Further DATVExpress Update

I now have some proper comms between the Linux host
and the PCB. EP1 is being used to download the FPGA
code and then for sending I2C commands to the various
chips on the board.

EP2 is being used in slave asynchronous mode with quad
buffering to communicate between the USB interface and
the FPGA.

I am getting more consistent samples across the USB
interface but am still dropping samples. It seems to have more
to do with the libusb-1.0 library than the FX2 firmware as
the buffer sizes seem to cause a behaviour that I was not expecting.
I think I need to know a bit more of how best to use the USB libraries.

UPDATE

It seems as if the sample dropping issue is being caused by how

my code internally queues it's samples, in other words the problem

can be fixed. Phew!!!

DATVExpress Update

I have had the DATVExpress board for a while now.
So far a small number of minor mistakes have been
found and fixed. The one outstanding problem is the
PLL for the modulator is not locking. This is due to a
misunderstanding about the circuitry around the chip
and is being fixed.

On the software side I have added code to my Linux
DATV transmitter program which allows me to download
the FX2 firmware to the board, start it running and then
download the FPGA code. All appears fine at the moment.
The next stage is for me to actually output something.

The first version of the FPGA code will simply write to the DACs
samples sent to it over the USB interface by the P.C. This will
be a very thorough test of the system. The final version of the

FPGA will not work that way (to reduce the USB load).

I hope the initial raw mode works as I would like to use the
board for DVB-T and DVB-T2 which will require use of the
a raw interface.

The modulator does produce output at 1.3 GHz but because
it is unlocked it drifts about the band. When that is fixed I
am hoping to be able to transmit some DATV with the board.

That is all for now, hopefully some news in the new year.

DATVExpress world exclusive!

This is the very first DATVExpress board in the entire universe.
Now the real work for me starts getting the software to work!