Inchworm not powering up

[Hedos]

Hi,
I just built my Inchworm.. after powering it up for the first time, nothing happens, no green LED lights up. My multimeter shows there's 0 volt across +5V and GND references, indicating the circuit must be shorted somewhere. So, I examined carefully each of my joints, making sure they were all good.. and I haven't found a problem.

Do you have suggestings on how to troubleshoot my Inchworm? What could have gone wrong?

Thanks a lot.

[Hedos]

Actually, if I check voltage between GND and the positive side of the power jack, I read the correct voltage (12.20 volts). Then, if I check just a little bit further, after the first power diode (D1), the voltage between this point and ground is 60 mV. Is this normal?

The voltage between ground and anywhere on the +5V segment on the PCB is 0 volts.

Voltage between the right or middle pins of the LM7805 and the ground is also 0 volts. (Left pin of the LM7805 is coonnected to D1, so 60mV too)

I also tested all diodes with my multimeter, they all seem fine (Block reverse current and otherwise allow current for >0.5V)

I also read 3.3kohms between +5V and GND references, so I think it's not a short circuit after all.

The LED has been tested and works fine too.

[Hedos]

I found the problem. It looks like that stupid universal adapter was outputting current in the wrong direction. (The interior of the plug was negative instead of positing)

The board works fine.. and that explains the diode thing.

[dipmicro]

You got it working ?

The green LED is powered directly from the Vcc so it should be on immediately after attaching proper power adapter.

Now that you have green LED on, it still only means that circuit is powered. Attach it to MPLAB, select proper serial port and have MPLAB reflash it with newest firmware.

Do not forget that the cable must be straight with all 8 wires, i.e. not just wires 2,3 and 5 (TX, RX and GND). I spent 2 hours troubleshooting my unit because I had only 3-wire serial cable and ICD2 requires control signals too.

[dipmicro]

Can you check if your cable is straight, i.e. Pin #1 -> Pin #1, Pin #2 -> Pin #2, etc. There should be 8 wires, pin #9 is unused if I remember correctly.

[Hedos]

Definitly not straight.. all mixed up.

Well, pin #1, #2, #3 etc. should be at the same (geometric) position on the male and the female ends, right?

And how come do they sell some straight cables and some not staight? Is there an obvious way to tell them apart?

[dipmicro]

Unfortunately there is no generic way to tell them apart only righ them through. Here is snip of the conversation I had with Bill, the author:

Quote:

Quote:What was the problem you're still having?

First problem was that I need the full straight cable. I had crossed and
simplified (RX, TX, GND). Secondly it did not work with MPLAB 7.20, or
it may have been that I did not restart Windows after disabling FIFOs on
RS232 port.

Btw. I got it working after restarting computer and updating to MPLAB 7.40. It may have just been one of those reasons (restart after disabling FIFOs or MPLAB version).

Also did not work with my USB/serial converter, must be native serial port, either built-in or extension card. Some models of USB attached serial port may work.

Here is Bill's answer:

Quote:The RS232 cable and or USB to Serial must be straight through.

I've seen PDA style USB / Serial that uses a female connector, this may not work. You need a male style RS232 just like your PCs serial port. Try hooking up your Microchip ICD2 to the serial port your testing.

Both the clone ICDs and genuine use 6 pins of the serial port.

GND, TX, RX, CTS, RTS & DTR.

DTR is important as it controls the 16F877s reset line.

[Hedos]

Ok, thanks a lot for the info.

It went a bit further now with a straight RS232 cable. I get a "Connected" message, then it keeps loading a bit and then tell me the connection has been lost. Here is the output:

"Connecting to MPLAB ICD 2
...Connected
ICDWarn0054: MPLAB IDE has lost communications with the MPLAB ICD 2. Would you like to attempt to reconnect?
Connecting to MPLAB ICD 2
...Connected
ICD0286: Unable to communicate with ICD
ICD0082: Failed MPLAB ICD 2 operation
MPLAB ICD 2 Ready"

What else could be the problem?

[Hedos]

I was playing around and tried "Download ICD2 Operating System".. it seems to have done it, it works now.

[Hedos]

Do you have some information on hooking up the Inchworm with me PIC? Do you know a web site or document that would explain well how this works?

I follow the Firefly designed and connected it that way:

PGC is connected to pin 12.
PGD is connected to pin 13.
+5V is connected to pin 14.
GND is connected to pin 5.
VPP is connected to pin 4, and also to +5V via a diode and 22K resistor. (Diode in the direction to less current pass from +5V to VPP of course).

But MPLAB still says: "Invalid target device id (expected=0x21, read=0x0)".