Re: [Usbpicprog-technical] Raspberry Pi PIC Programmer Help?

[Will M. <wm-...@sw...>]

Hi Frans,

Thanks for you interest!

The raspberry Pi output is 3.3V (according to 
http://elinux.org/RPi_Low-level_peripherals, and confirmed with 
oscilloscope if I recall correctly)

 From my reading of the Programming spec, I can't find any mention of a 
12V VPP, just a 3.3V on 'VDD during programming' in the table in section 
7.0. The chip also has an internal voltage regulator to ramp the 3.3V on 
VDD to 2.5V needed on 'VDDcore' with an extra tantalum capacitor.

Programming Spec:
http://ww1.microchip.com/downloads/en/DeviceDoc/39934b.pdf

I'm quoting sources not because I want to prove my point, but because I 
don't know what's wrong and you may be able to explain - if one of my 
sources is inaccurate that would explain a lot!

Those two bits put together made me think it would be very easy to use a 
Pi for this project - almost no extra components required.

Will.

P.S. In case you want to read more, here is a link to the Microchip page 
for this Pic. ;)
http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en536119#documentation

P.P.S. If you would like me to try and compile USB PIC Prog on the Pi, I 
shall try it some evening this week, but unfortunately I don't have a 
programmer to test it with.




On 29/01/13 16:33, Frans Schreuder wrote:
> Hi Will McElderry,
>
> It sounds nice, but how do you plan to convert the voltages (5V -> 3.3V)
> and how do you supply the 12V programming voltage?
> I guess you will need some additional hardware.
> It is possible though to run usbpicprog on the raspberry pi.
>
> Regards,
>
> Frans
> On 01/29/2013 01:33 PM, Will McElderry wrote:
>> Hi All,
>>
>> I'm attempting to use the GPIO pins on the Raspberry Pi to program a
>> PIC24FJ32GB004, and struggling.
>>
>> I've had some success, but I can only clock out 0's from the Visi
>> register (see note below).
>>
>> I am hoping that someone on here may be interested in my goal enough to
>> lend me their knowledge and perhaps try running the code on their Pi to
>> program a chip?
>>
>> Any comments on what may be wrong or ways to test further would be
>> appreciated!
>>
>> The code is very basic and hacked together, it's C++ and easy enough to
>> read.  I've compared with the usbpicprog code and I can't see any
>> noticeable differences.
>>
>> I'll post more details if there's anyone interested.
>>
>> Thanks,
>>
>> Will McElderry.
>>
>> NB: I *believe* I am clocking out zeros from the register as PGD seems
>> to accept current when the PIC should be transmitting data - indicating
>> the PIC is intentionally holding the ping low.
>> This was a fortuitous discovery thanks to only having access to an
>> oscilloscope with one channel, and using a r/2r ladder to allow
>> monitoring 3 pins at the same time. When PGD is not connected to either
>> zero or one the output voltage on the channel changes noticeably, a
>> state I have been able to induce intentionally by sending invalid
>> commands to the PIC, or not requesting clocking out of the Visi
>> register, but asking the Pi to try and read from the PGD pin.
>>
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