any way to test a PIC IC? / inchworm debugging

[montreal assembly]

Hi

i am trying to setup an inchworm+ but i cannot get any programs to connect to the IC. I have tried MPLAB and Tiny PIC bootloader and neither will see the chip i have that came with the kit from blueroom. The PIC is 16F877A. I checked the voltages on the serial port of my computer and i think it is working ok.

I had a problem with the inchworm board originally where the MAX232 chip was pulling excessive current so i replaced it and it seems to be ok now but is it possible the PIC was damaged at this point as well?

so what im wondering is if there a way i could throw the chip on a bread board and take some measurements of something to see if it is functional or not?

i have never had it working so i am not entirely sure it is the chip but i *think* everything else is setup correctly. (yes i disabled the fifo buffer in windows and read and reread the instructions included AND i did a continuity test on every pin of my serial cable, it looks good)

any help is much appreciated.

scott.

 

[blueroomelectronics]

The 16F877A is pretty robust. Do you have a oscilloscope? Is the crystal running?
It takes very little for the communications mode to work. This may seem like a dumb question but do you have access to a PIC programmer? The firmware for the 16F877A can be found in the download section of my site.

 

[August Treubig]

Experience Says

Like Bill says, if you have power and ground, the oscillator should run. If it is running, the pic should fire up fine.

Silly question, but valid, as I once put a pic in wrong in an FM transmitter.

Is the 16F877A plugged in in the correct direction. The notched end should be closer to the serial port.

 

[montreal assembly]

hmm no i dont think there is a clock happening. on pin 13 i have a voltage of a bit less than 1 and on 14 about 2 volts on the scope and no square wave.

i do not have access to a pic programmer unfortuantely.

but maybe we have found the problem.

scott.

also yes i have double checked the direction as well but that is always a good suggestion. sometimes i solder sockets in backwards even. and then it looks like the right way but really...


also i dont know if this is relevant but the led beside the clock silk screen (busy) is never on. but i dont know if it should or shouldnt be at any time.

 

[August Treubig]

Busy LED

The only time it is on is when the Inchworm+ goes to do something with the attached PIC. So, no it won't be on when you power it up. But the other one should be.
Make sure that pin 1 MCLR is not grounded.

 

[montreal assembly]

ah ok isee. actually i was wrong about the clock i think. i was thinking i was looking for a nice square wave but i wasn't thinking about that it is a crystal and will be a much smaller wave. which seems to be there.

but your suggestion about pin 1...

when i dont have the serial cable plugged in its 5 volts but when i plug it in it goes to -.7 volts. so maybe my computer port is not ok after all? or is this what should happen?

 

[August Treubig]

Voltages ok

That is what happens when I rip the Unicorn off and plug it in serial. Powered up by itself pin 1 = 5v. Plug in the serial cable = -.7 or so. Bring up MPLAB and set communications up to serial and connect = 5 v plus, in my case, it decided to download a new OS to it, so the red led lit up.

 

[montreal assembly]

HI

thanks for the help.

heres what happens. when i connect with mplab the voltage goes to 5.6 but then fails and i get some error msgs. if i try to connect again manually it just stays low.

umm i tried to post a link to some screen shots but it wont let me post for some reason if i do.

but here is the url i guess copy and paste. it has the corresponding voltage at pin1 in the comments

**broken link removed**

 

[blueroomelectronics]

Hmm, can you try to download OS?
Are you using COM1 or COM2? Did you reboot after changing the FIFO buffers?

Pin #1 on the 18F877A is diode clamped so in reset it's normal -0.7 the MPLAB toggles reset / run.

 

[montreal assembly]

yes i have been trying to play around with settings for about 2 days. i can get other error msgs like failed to open port as well but never a successful connection. i am using com1. in my bios on the pc the serial port is also set to com1. the serial port shows up in hardware manager.

my motherboard does not have a soldered on db9. it has just pins sticking out for a header. so i have a ribbon cable with a header going to a db9 male panel mount on a pci card bracket type thing. according to the manual i have the header oriented correctly but i have tried reversing it anyways and at that time it didnt seem to be working.

i checked the connection between the header and the panel mount connector for continuity a few days back and it seemed to be ok. maybe tomorrow i iwll go over everything again to be really really sure.

also i read about making a loopback connector to verify the port. i dont knwo how to run a test though but i could definitely make the connector without much trouble.