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Help with circuit(programming pics)

That's right, you FIRST get a real programmer that works and then you can compare your circuit's behavior to one that works.

I'm not the one hollering for help continuously. You can think I'm a horn-tooting dick if you want, but I've been programming PICs for over six years. You are but one individual in a long list of people that I've seen trod down this path at the beginning of their PIC experiences. I suggest you sign up at

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if you haven't already.

Ok, but do you know why it works now and it didn't before?

Long skinny power leads will definitely give you headaches with a PIC. The datasheet is very clear about Vdd rise times, if you violate them the PIC will not come out of RESET. Also decoupling across the power pins is necessary on the "nanowatt" parts.

It's not rocket science, but then it's not a piece of cake either. If you don't like my opinions, go ask the 3000 people at

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I'm sure Olin would be more than happy to help clear this up.

It's a tad more complicated than that. As people have already told you, rise times and timing in general are very important. Also some PICs require Vpp BEFORE Vdd, some require it afterwards. Then there is LVP and all it entails. Even revision 'A' parts can have major differences in the programming algorhythm.

Reply to
Anthony Fremont
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Seems to be the DMM ;/ I have a cheap one that I used(cost like 2$) and it seems to somehow be interfering with the signals. When not used I can program a pic chip and but when I hook it up I can't program ;/

My other DMM, which is a much better one doesn't seem to have that problem. (well, its measuring the power supply current so not sure if it would cause the same problem with when used on the parallel port)

Reply to
Jon Slaughter

It's loading the pins down thru low-impedance and/or capacitance and screwing up the shape/amplitude of the signal.

Reply to
Anthony Fremont

Ok, It seems to mainly be the resistors in the circuit. 2K and below work but above that it doesn't seem to. I'm not sure why such a low resistance is required unless the capacitance of the pins is quite high. (slowing down the transfer rate doesn't seem to help)

It seems that using mosfets are ok except that the when the pic is not being programmed and if there is no shutoff method then it uses an excess amount of current(about 30mA when not programming and 3-4mA when programming).

Reply to
Jon Slaughter

There's L in the wires too, not just C. The capacitance of the pin itself is on the order of about 5pF. I keeps tellin' ya, it's all about the rise times. :-)

If the PIC is unpowered and you apply voltage to any pin besides /MCLR (it's special), then current will flow thru the protection diodes and onto the Vcc rail of the PIC (and likely it's associated circuitry). If you're pushing

30mA thru the protection diodes, then you are risking serious damage to the PIC.
Reply to
Anthony Fremont

FYI: A Pickit2 programmer is 35 bux from Microchip.

Reply to
Tom2000

On a sunny day (Tue, 30 Oct 2007 17:55:45 -0700) it happened Tom2000 wrote in :

Lots of people have been saying this, but to the defense of the OP, I think it is good to write your own prog soft, and build your own hardware. Anyways I went that way too, the experience obtained has more value then 35$. And it was fun to do.

Reply to
Jan Panteltje

Totally agree. Besides, it is much better to learn by fixing the mistakes of your own rather then live with the bugs and the inconveniences created by somebody else.

VLV

Reply to
Vladimir Vassilevsky

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