Dangerous Prototypes Open Source Hardware

Logic Shrimp done, but having issues

June 10, 2011, 01:57:56 am

http://http://i.imgur.com/TBkcu.jpg

I built my Logic Shrimp (had flux this time for those who read my last post), but I am having issues.  When I plug the USB port in, the activity light stays on and I cannot get the Jawi client to connect to it. 

I programmed the bootloader with my Bus Pirate with no issues, then used the bootloader to program the 1.3 firmware, then later the 1.2 firmware for testing.  I also tried programming the entire dump with the Bus Pirate as well.  The COM port shows up in device manager when I use the inf provided by the package. I am not sure how to proceed with troubleshooting.  Any help would be appreciated.

Re: Logic Shrimp done, but having issues

Reply #1 – June 10, 2011, 03:41:58 am

first, check with some magnifying glass it looks like you have some solder bridges on the PIC.

If you are able to program the mcu, you need to first check if the usb data lines are properly connected and that there's no solder bridges.

Secondly, check if you get output from oscillator - on my board the oscillator output pin (diagonally from pin1 of the oscillator) was connected to ground. Use a multimeter and check if that pin is connected to ground if it is check the trace, it goes under the oscillator, trough that so23-5 IC6 and into pic. Make sure you have no solder joints on pic and that clock is not linked to the ground.

Those are only two things that will prevent the pic to enumerate if it is properly programmed.

Now, there is always the possibility that you didn't program it properly. If you programmed bootloader in to it you need to connect PGC+PGD pins before you attach it to USB and only then bootloader will kick in and your device will enumerate. On the other hand if you programmed the firmware hex into it, it should enumerate automatically.

Re: Logic Shrimp done, but having issues

Reply #2 – June 11, 2011, 05:17:08 pm

Got it working.  There were some bridges from the ground plane to the clock trace for the memory chips, similar to the way that your oscillator output was bridged to ground.  A couple small cuts and everything was fine.

Thanks for your help.

Re: Logic Shrimp done, but having issues

Reply #3 – June 11, 2011, 05:50:10 pm

great, glad it works :D

btw did your board had a "red mark" on any of the sides? (red mark means that board is "electrically checked" by the manufacturer so it's important to see if this type of errors ever happen on checked boards or only on unchecked ones)

Re: Logic Shrimp done, but having issues

Reply #4 – June 11, 2011, 11:00:48 pm

There are no red marks, so it wasn't electronically checked.

Re: Logic Shrimp done, but having issues

Reply #5 – June 11, 2011, 11:12:59 pm

[quote author="Segfault"]There are no red marks, so it wasn't electronically checked.[/quote]

that's good :)

btw have you checked for bridges on the pic where I circled them, I can't say from the pic it is maybe good but be sure to check them :). Cool to have it working :), I think it is the most useful tool on my desk attm :D

Re: Logic Shrimp done, but having issues

Reply #6 – June 12, 2011, 08:29:32 pm

I did look at what you pointed out and it was tiny pieces of cotton from cleaning up excess flux.

Re: Logic Shrimp done, but having issues

Reply #7 – June 12, 2011, 09:18:28 pm

:D I said I seen something :D :D :D

anyhow, important it works now ... hopefully others will learn from us and first inspect the board before they start soldering

Re: Logic Shrimp done, but having issues

Reply #8 – June 13, 2011, 02:19:38 pm

Thanks for writing up your problems -- I was assembling a logic shrimp PCB last night and (esp. after my problems with the IR Toy) it was good to have some things to check before all the parts were in the way.

But it turned out my board was fine (e-checked, and no unexpected shorts-to-ground).  I'll be posting by own pics soon, if I can get it working.

Re: Logic Shrimp done, but having issues

Reply #9 – June 14, 2011, 02:41:50 am

Here's a photo of the one I put together.  I managed to bridge *all* of the pins under the USB connector, and that was a major pain to clean up.  There's just so little room for getting the iron under there.

The cables I use for programming are tied up in another project (maybe I'll write that one up soon), so I can't program it at the moment, hopefully before the weekend.

Re: Logic Shrimp done, but having issues

Reply #10 – June 14, 2011, 02:42:40 am

I also wanted to gripe about TSSOP.  After some of that, SOIC is such a breeze!

Re: Logic Shrimp done, but having issues

Reply #11 – June 17, 2011, 02:19:38 pm

I'm trying to get xaught up. Did you all get new PCB codes?

Re: Logic Shrimp done, but having issues

Reply #12 – June 17, 2011, 03:44:28 pm

Not yet.  But no worries, you've had quite a lot going on.

I tried this one out a little last night, but I think there's a problem with my voltage regulator.  It was getting very hot and only putting out ~0.8V, so there may be a short or a bad connection in there somewhere.  MPLAB was also complaining when I tried to program it that MCLR was held in reset. 

I'm refinishing my basement, so I don't have a lot of time to look at it.  I want to make a USB power cable with breakouts I can hook my current meter up to, so I can test current draw when debugging USB devices (and so I can drive them from a separate supply when I'm working out the kinks, lest I smoke my USB ports...).

New forums seem very snappy, by the way.  I can definitely tell a difference.

Re: Logic Shrimp done, but having issues

Reply #13 – June 17, 2011, 05:05:22 pm

Sorry about that - coming at you via PM.

Re: Logic Shrimp done, but having issues

Reply #14 – June 20, 2011, 01:42:29 am

No code for me yet either.  Thanks Ian.