[Usbpicprog-technical] Portable programmer

[Charles K. <cha...@fr...>]

Hi Frans

My aim is to modify the usbpicprog into a portable programmer so that I 
can download my code into an external eeprom, remove the usbpicprog from 
the pc, then program my target using the usbpicprog as a stand alone 
programmer.

I have added an eeprom (24LC64) to the usbpicprog board (I did forget 
the 2 x 10k pull up resistors on the SCL and SDA lines but have added 
them as a mod on the board), a pushbutton switch and a 5v regulator. As 
you can see from the schematic I used the pic sda and scl lines for the 
eeprom and changed the pgd and pgc lines to pins 17 and 18 respectively. 
I changed the firmware to use rc6 and rc7 and can program external pics 
with no problem.

Unfortunately I can not seem to program an external eeprom (connected to 
pgd and pgc) or the on board eeprom (using sda and scl). monitoring with 
a scope I am getting activily on the clock and data lines but I suspect 
my timing is out. I have tried software and hardware I2C routines with 
no luck.

I was thinking that if the usbpic prog did not detect an external pic, 
(or one could have an option in the pc programming software) it could 
dump the program memory, data memory and config bits to the eeprom. when 
the pushutton is pressed, to read the data from the eprom as though it 
were coming from the usb port and program the target.

Unfortunately I am stuck and not too sure how to proceed.

Do you have any advise and could you help with the firmware modifications.

Kind Regards


Charles Kerr
ch...@cr...

Cape Town
South Africa