Still struggling to get mine working. I'm currently running USBmon but I'm struggling to understand it. Can someone take a look at this screenshot...
I think that tells me that the 4550 is talking to my PC, can someone confirm that please?
I did a data log but didn't see any packets from 0x82 but maybe I was doing something wrong?
Is there a way that you can send a specific message to the 4550 and look at the reply it gives?
I've been through the PCB under a BIG magnifying glass and tested for shorts. My thoughts are that maybe I can diagnose the issue from reading the USB data... with a little help from my friends
Added after 3 hours 6 minutes:
I've been doing some thorough checking around my non-working board (Potyo's Vn2) with many ICs removed.
I've had no more input yet but I think that the USB is communicating (see earlier post with screen capture from USBmon). Indications seem to suggest a hardware or software issue with the 877A.
Software Thoughts
Someone called Jim sent me a message saying
For me the problem was in the 877a in that it could not comunicate with the 4550 properly using the boot program, not sure of the exact file off the top of my head. Also not knowing any more about the boot issue I tried the 661.hex and it worked.
Hope this helps.
but I don't understand which file he's referring to when he says that he used the "661.hex file" to program his 877A.
Harware Thoughts
One thing that concerns me is to do with the 3 way jumper. Potyo says to set this so that it's nearest IC5, the 74HC4066 but that means that the full VPP (up to 14V) is sent into pins 5, 13, 12, and 6 of the 74HC4066 via CMOS-EN. I have used a 74HC4066E and I looked at the data sheet. The Max DC supply voltage for this device is 10.5 V so it looks like this IC may being sent too many Volts. Should I be concerned? Should I put a resistor from the 3-pin jumper to the 4066 input pins? Have I used the right device? Maybe there's a different version that handles the extra Volts?
I checked that the VPP inverter was running. I removed the digital pot chip and put a 10k pot between pins 5 and 6; watching VPP while I turned the pot, it ranged between 10.4 and 14.2 Volts - I think this is good. FYI I used a 150uH inductor (see picture of my board in earlier post).
I checked the operation of MCLR for the 877A via Q4 and it works fine - ranging between 0.6 and 4.89 V when you take Pin 36 of the 4550 to +5v or ground.
Also, there is no connection to Pin1 of J3 but, depending on the setup for a target board via the ICSP I believe that pin 6 might be needed. Is this correct?
Has someone reading this actually made the Potyo Vn2 board as shown on Page 28 of this thread and made it work? I downloaded the Eagle files and printed the PCB directly from Eagle CAD. I also ran the Electrical Rules Check and it seems to say that all is OK, at least the schematic and the board are consistent.
Once I have mine working, I will publish a full set of documentation on how to trouble shoot this puppy.[/quote]
Added after 1 hours 43 minutes:
OK, I now realize that this will likely get glued on the end of my previous post but I wanted to tell y'all that.....
I MADE IT WORK!!!!!
The problem was Q4 but there were several things wrong...
I must be going crazy in my old age, Q4 is a BC237, Q1-3 are BC327s but I got it into my tiny brain that they were all BC327s. BIG mistake as BC237 = NPN and BC327 = PNP.
As I said above
I checked the operation of MCLR for the 877A via Q4 and it works fine - ranging between 0.6 and 4.89 V when you take Pin 36 of the 4550 to +5v or ground.
Well that was true but only when there were no ICs in the sockets and I have no idea why it worked in that situation. By chance I tested Pin 1 of the 877A with a meter and found it was at 6.3 mV, clearly it needed to be at +5V. I removed the 4550 but left the 877A in place and tried to make Pin 1 MCLR go between 5 and 0 v by connecting Pin 36 of the 4550 IC socket to 0 and 5 v but Pin 1 of the 877A stayed low which started me looking very closely at Q4 and the surrounding components.
Anyway, I put a BC237 in as Q4 but in triple-checking everything I realized (as has been said earlier in this thread) that Q4 is shown in the wrong orientation in Potyo's V2 Eagle CAD board file; the flat side should face the 4550, not the 877A.
so... a
BIG THANKS to Potyo and all the others that made this possible. Here's a summary of my Output data....
Auto-connect not enabled - Not connecting (Try enabling auto-connect on the ICD2 settings pages.)
Connecting to MPLAB ICD 2
...Connected
ICD0082: Failed MPLAB ICD 2 operation
MPLAB ICD 2 Ready
Running ICD Self Test
ICD0082: Failed MPLAB ICD 2 operation
Running ICD Self Test
ICD0082: Failed MPLAB ICD 2 operation
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
Downloading Operating System
Connecting to MPLAB ICD 2
...Connected
Setting Vdd source to target
ICDWarn0020: Invalid target device id (expected=0x4D, read=0x0)
...Reading ICD Product ID
Running ICD Self Test
... Failed Self Test. See ICD2 Settings (status tab) for details.
...Download Operating System Succeeded
MPLAB ICD 2 Ready
Running ICD Self Test
... Failed Self Test. See ICD2 Settings (status tab) for details.
It says in the status window that the target MCLR Vdd is low but I think that's cos there's no target connected and I've set it so that the target supplies its own Vdd???
My question about the HC4066 voltage and the 3-pin jumper above still stands; Potyo???