check out this site
check out this site
But its not easy to build, lots of designs are much easier, its too big for whats needed for most ppl.
All you need to program 90% of the time are f88's etc, few resistors and a diode or two etc, no circuit board etching / drilling / soldering
Sorry the title description does not hold true.
look up com84.gif - now thats an easy to buld pic programmer.
And lpt port programming has caused lots of headaches due to port mode and timing issues of fast cpu's
Serial has none of those problems.
I wouldn't be so harsh. For starters, you certainly don't need to make a circuit board, that's plenty simple to make on a perfboard.
I use a similar parallel port programmer, but even simpler:
The com84 is very simple, but doesn't support the 18Fs I needed.
I've not used the 18f's, but I am interested in why simple serial wont support it.
Don't know why, but I've never really looked into it too much either. The com84 programmer only supports 16F84s (thus the name, I imagine). There are certainly serial programmers that support the 18Fs, such as the JDM programmer, which isn't all that complex but not quite in the same league in terms of simplicity.
I started with D-Tait programmer years back. Heckshaer, com84, then built the EL-Cheapo after realising I needed more features. Then realised I needed to start coding so I bought the PICKIT1, this wasnt enough as it only support 16-pins. Went for the velleman PIC programmer, used it for 6 months or so...it doesnt support the newer PICs and dont integrate with MPLAB.
In the end I built a decent one, an ICD2 clone. Have been happy with it from the day I powered it up. So happy with it that Im considering buying the original.
For those who dont know, I have posted a PCB diagram for it.
Was it a waste of money building all those? well it wasnt as those where the only build it yourself circuit I can find then. It did the job ok back then.
Since theres plenty of good circuit around the net now, my advice is...build a decent programmer that support many chips while you are at it. Unless you are not planning to do more with it.
Simple serial will work if you do it right. Powering off txd is wrong unless you provide a GOOD filter. 10uf isn't enough. Use a power block instead for power.Quote:
Originally Posted by lez
Also, never trust the serial port voltages and edge rates. Always buffer with a proper rs232 transceiver like the max232 (has the charge pumps internal and only requires 5V).
Also, the PICs use software to emulate a uart. The problem is if the internal osc has a frequency that is slightly out of range, then you will not be able to find a baudrate that will work reliably. Remember that the PIC is using a small bootstrap to program itself.
Originally Posted by widower
Most PIC have a built in HW UART these days. Only the old ones and the really low end PICs dont have them built in such as the 12C508s and 16F84s.
The PIC can only be programed via the UART (HW or SW) only if the bootloader had been loaded. Bootloader code is normally used for maintenance reason and it is optional.
The PGC,PGD and MCLR are the pins that are used to program the blank PICs and no OSC or what so ever is needed at this stage, just a 5V supply.
I think you are getting confused with programming the PIC with a bootloader via serial port. The serial programmer being mentioned uses the proper programming pins of the PIC.
A decent serial programmer can be found here
http://www.sparkfun.com/shop/index.p...=400325&cat=3& then scroll down to the PIC-PG2C. Works fine on a desktop, just not on a laptop. Also has links to free programming software.