I made a simple programmer that is basicaly identical to the one found here:
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I can sucessfully program the 16F688 using WinPic but not the 18F4431. I setup the pins(since they are not the same) and grounded the LVP pin on the
4431 but no matter what I do(trying many different settings in WinPic) I cannot get anything programmed on it. From reading the programmign specs for it I figured they are the exact same(using ICSP method)? Is there something I'm missing???
I am using the LF version so maybe that makes a difference? What could be the potential problems(remember, it works for the 16F688 with no problems...) that I should look at? Maybe not enough juice?(should be ok... one thing I have noticed is that the clock and data lines seem to be a little lower than the 688....)
no, these both PICs are not identical in the programing algorithm. But WinPIC comes along with a configuration for the 18F4431. Did you get the latest version?
yes. What I mean by identical is the hardware side of it... that is, they are virtually identical in that you can use the same method and ic's to do both and one doesn't require any more "hardware" than the other.
Now I hope to understand you. I just take a look at the programmer you build, and I think in general, this isn't a good choise. There is no switch for Vdd on the PIC, but for some PICs you need explicit a Vpp-first sequence to ensure, that you can enter the programming mode, and some other chips (like 16F688) need this sequence in some cases of configuration. From the programming specification there should be no needing for the 18F4431, but sometimes a test could help.
An other problem can be the voltage of the low level on Vpp. On my practical experience some chips need a low level that is much lower than
0.8V (12F629/675 for example). So check your circuit.
I build this programmer (is also supported by WinPIC):
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For some chips I placed a diode in the line to MCLR, if can't enter programming mode.
So far with my ideas, because I don't have a 18F4431 here, I can't say anymore about the problem.
Winpic handles that though... you can tell it to raise the Vdd before the Vpp or after.
Well, would you have any idea why the PIC18F2455 can be programmed and the PIC16F688 but neither the PIC184431 or the PIC18F4680 can be programmed? The only difference is there physical size but by the FLASH programming documents they all give the same method of programming them(hardware wise atleast) so I can't understand why the 2455 works but the other 2 don't(the
688 is a little different but)... The documents don't state there is any programming different and lumps them all together, therefor I can't understand why it isn't working... I assume winpic can handle them since it says it can but I can't find anything wrong with my circuit either....
I would assume, if say, the larger IC's needed more current or something like that then the docs would mention that... yet it treats them as being identical, except for pin layout, to the 2455 and others...
If you have a 16F876 or 16F877, this could be an option for you:
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It is a sipmle clone of the Microchip ICD2 with RS232 port only. I build it because WinPIC at this time could not programm 18F* and I interestend in debugguing the chips directly, and because simulation in MPLab is a little buggy. The "A" types of the chips (16F876A or 16F877A) works too, but the firmware must be patched therfore.
huh? This makes no sense? The programmer is indepedent of what you call Vdd or Vpp so it doesn't matter which one is raised first(you could just swap them).... so I have no clue what you are talking about.
I might try it but it still doesn't explain why I can program the 18F2455 but not the 18F4431/4680 and your response above doesn't jive with that.
If you read the programming specs from different PICs sometimes, it may help to understand this.
In short: On "Byron Jeff's Trivial HVP Programmer" there is nothing to switch the Vdd for the PIC separate (by the programming SW). But, for some PICs e.g. 12F629 you need this in any case, and for some PICs e.g.
16F688 in some cases, to reset these chips by raise Vpp before Vdd! Otherwise, the chip will not enter programming mode and looks like a damanged.
This should be only an additional information to you, because you use
16F688.
I gave this suggestion, because I can't see any problem from here. There may be an problem in WinPIC (not all 18F chips configurations are testet) or something ohter. So it may be a option, to have an other programmer.
? The software can assert the Vdd high or low and can assert the Vpp high or low... it can do this in any order it wants.... Vdd is ran from a parallel port i/o just like Vpp... You can raise either one first because they are controlled by the parallel port.
ok. I see what you are talking about. I'm not using that exact programmer. Sorry I wasn't paying to much attention... lol. In my programmer I can control the Vdd on and off using winpic. I'm not sure why he didn't add that ability though. In winpic you can get a parallel port i/o to act as Vdd just as you can with Vpp and then you can tell winpic which order it should use. Basicaly, with his THVP he doesn't use D3/Q3 pair but you could use it to control the Vdd. I think this is cause he uses a serial interface while I use the parallel port.
In any case I don't have the issue you pointed out with his programmer since I don't use that exact method(but it was based off it when I talked to him in another NG about it).
Well, actually I'm trying to use the other PIC's. I have only gotten the
16F688 and 18F2455 working but not the other two(18F4431 and 18F4680). I still cannot understand why I can program the 2455 but not the 4431... the flash programming spec is suppose to cover all of them(i.e., the method is the same for the 2455, 4431, and the 4680). This might point out that there is a problem with winpic or my circuit.... maybe it has to do with the clock speeds and stuff... maybe the programmer method I'm using(very similar to the THVP) is not working well and it just is "coincidence" that I can program the first two but not the second two...
Again though, what really confuses me is why it works for the 18F24555 but not the 18F4431/4680.... the only difference I can see is that the last two have a greater number of pins and is physically larger but I don't see how this would affect its programming method.
(i.e., it would be nice if someone could tell me why a programmer would work for the 2455 but not the 4431 so I'd have some idea if it could be the programmer or not.... cause reading the specs implies they are identical w.r.t programming and this then leads me to believe that it must be winpics problem... but surely its much more likely that its my circuit)
Well, I assume I did. The pin configuration is almost the exact same for the 2455 as the 4431 and I've tried it several times from scratch... possible that I kept making the same mistakes but not likely.
Well, I was just hoping that someone either had a similar problem or knew of a difference that would cause it not to work right. I'd imagine that the PIC18 series is a popular pic but seems not ;/ Or maybe just no one has had any problems with it ;/ In any cause seems like I'll have to figure it out myself ;/
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