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 Post subject: JDM Programmer for PIC18F2550 28-DIP
PostPosted: Tue Jun 27, 2017 5:33 pm 
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Joined: Tue Jun 27, 2017 4:43 pm
Posts: 3
I built the JDM programmer shown at http://picpgm.picprojects.net/hardware. ... PROGRAMMER. This schematic is for a PIC with only 18 pins, so I tried my best to adapt it for the PIC18F2550, which has the pinout shown below.

I basically connected every pin that isn't specified in the schematic to VSS to keep it from floating.

PICPgm doesn't recognize my programmer. Can anyone explain what I might have done wrong? I'll be happy to provide more details if necessary.

Thanks.


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 Post subject: Re: JDM Programmer for PIC18F2550 28-DIP
PostPosted: Tue Jun 27, 2017 8:46 pm 
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Joined: Tue Jun 27, 2017 4:43 pm
Posts: 3
I've gone over the hardware with a DMM, and it looks like the build is ok. Here's some node voltages I thought would be of use.

Serial pin voltages relative to GND, not connected to circuit
TxD:-10.7V
GND:0V
CTS:0.08 (probably floating since it's an output)
DTR:-10.7V
RTS:-10.7V

It doesn't seem like my serial port is too underpowered, as is the case on some laptops.

Q1 voltages relative to AGND (lowest node on the schematic: C2-)
C: 4.74V
B: -0.72V
E: -0.44V

It seems to me like TxD isn't doing what it's supposed to be doing, namely, switching the transistor for charge pumping to get MCLR* to 12V. But maybe that isn't necessary for the programmer detection? If anyone knows how detection works and what I can test to see what's wrong, please let me know. I'll try to see if I can observe a signal with my oscilloscope upon PICPgm startup, rather than the DC values that seem to be on the serial cable right now.

I've also noticed that if I let PICPgm autodetect the port, it'll try and fail to get parallel port I/O drivers, despite my computer not having a parallel port. There's no such error message when I specify COM1, only "Error! PIC Programmer not found! Check connection!"


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 Post subject: Re: JDM Programmer for PIC18F2550 28-DIP
PostPosted: Wed Jun 28, 2017 11:04 pm 
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Joined: Tue Jun 27, 2017 4:43 pm
Posts: 3
Solved. It was a hardware problem. I think GND was shorting to something it shouldn't have been, and one of my diodes was going to the wrong serial pin.


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