[hpsdr] FW: hpsdr] [FPGA_USB] Review/Comments FPGA_USB Board -April 5, 2006

[pvharman at arach.net.au]

Hi Chris,

I did manage to get the 10 bit A/D converter on the 18F4550 to act as a mic 
input and send it over the USB interface to the PC. Bill, KD5TFD wrote some 
Java code that read from the PC side (the 18F4550 looks like an additional COM 
port) and allowed me to view the data. 

It was very obvious then that the Full Speed USB was not going to be fast 
enough for all the functions we wanted in the HPSDR. 

The 18F4550 needs its USB port to be continually polled so your code becomes a 
state machine. I wrote quite a lot of test code for the chip and I think it is 
fine for a project were you want to replace an RS232 interface with USB. 

The FED C compiler, which at the time we started was the only one that 
supported the USB on the 18F4550, was and is full of bugs, even for a hobby 
project I would not use it. That's a shame since the concept is very good and 
the simulation facilities, if they always worked, would be a great help.

I've written quite a lot of C code for the PIC in the past and have always 
used the CCS compiler - also has plenty of bugs but you could usually find a 
stable release and resist the urge to take the next upgrade - not sure if they 
support USB on the 4550 as yet. 

Let me know if you want my sample code for the FED compiler. 

73's  Phil...VK6APH 


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