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Step 7For my fellow PIC-heads: Breadboard with built in ICSP
Microcontrollers are being incorporated in a growing number of DIY projects. During the development process, a chip may have to be reprogrammed many times.
I don't know if the same thing applies to AVR's, but most every 8 and 14-pin PIC (as well as many of the 20 pin ones) share the same pinout for the programming lines. So I have dedicated a breadboard just for development of these PIC's.
The technique here is the same as that used to connect the power/ground buses. After peeling away some of the backing, you can permanently wire your programming connections and port them out to a standard header. You can also connect your power and ground pins to the appropriate rails and add a chip capacitor while you're in there.
You'll also notice some extra circuitry next to the programming header. Well, the same pins that are used for ICSP can also be used by the micro as normal input/output pins or other functions. If you are using those pins in your project, then you may very well have to connect/disconnect your programming cable each and every time you change and update your code. I have found, for instance, that the PICKit2 programmer holds the programming lines low when the programmer is inactive. Rather than put up with this, I have connected the data and clock lines through signal relays which are only closed when the programmer supplies power to the Vdd rail. The power goes through a rectifier diode so that when only external power is used the relays remain open. The HVP line doesn't get a relay to itself. Instead it is simply diode rectified, so that when it is not active it does not pull the MCLR line low. There is also a programming button at the top left of the board. This simple Instructable shows how I did that: http://www.instructables.com/id/PICKIT2-programming-button-mod/
*Edit: Since publishing this, I've been informed and have also personally confirmed that the Vpp line on a PICKit2 becomes high impedance when inactive, so it does not actually need to be diode-rectified for circuit-isolation; all I have achieved is to remove the ability of the programmer to do a hardware reset of the MCLR line (which hasn't bothered me so far). Oh, well.. I needed a jumper for my pcb, anyway, and the diode was the perfect size. :P
**update: wow, that method of clock/data isolation is sooo last year. Check out the latest pic.
I don't know if the same thing applies to AVR's, but most every 8 and 14-pin PIC (as well as many of the 20 pin ones) share the same pinout for the programming lines. So I have dedicated a breadboard just for development of these PIC's.
The technique here is the same as that used to connect the power/ground buses. After peeling away some of the backing, you can permanently wire your programming connections and port them out to a standard header. You can also connect your power and ground pins to the appropriate rails and add a chip capacitor while you're in there.
You'll also notice some extra circuitry next to the programming header. Well, the same pins that are used for ICSP can also be used by the micro as normal input/output pins or other functions. If you are using those pins in your project, then you may very well have to connect/disconnect your programming cable each and every time you change and update your code. I have found, for instance, that the PICKit2 programmer holds the programming lines low when the programmer is inactive. Rather than put up with this, I have connected the data and clock lines through signal relays which are only closed when the programmer supplies power to the Vdd rail. The power goes through a rectifier diode so that when only external power is used the relays remain open. The HVP line doesn't get a relay to itself. Instead it is simply diode rectified, so that when it is not active it does not pull the MCLR line low. There is also a programming button at the top left of the board. This simple Instructable shows how I did that: http://www.instructables.com/id/PICKIT2-programming-button-mod/
*Edit: Since publishing this, I've been informed and have also personally confirmed that the Vpp line on a PICKit2 becomes high impedance when inactive, so it does not actually need to be diode-rectified for circuit-isolation; all I have achieved is to remove the ability of the programmer to do a hardware reset of the MCLR line (which hasn't bothered me so far). Oh, well.. I needed a jumper for my pcb, anyway, and the diode was the perfect size. :P
**update: wow, that method of clock/data isolation is sooo last year. Check out the latest pic.
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