I let the smoke out of something :-(

I was a little tired and hooked up one of the bipolar steppers to start working on some interface stuff... I inadvertently hooked the +15v external power to the Din (0-3 or so I though) side (Vin/Grnd) that was jumpered to +3.3v off the board. The board came on and started running (without the USB plugged in or other power supplied) ran for a few seconds and started smoking... Some initial testing it looks like I only fried the buffer chip on the Din, however I am seeing some very odd behavior. Testing the Din pins 0-6 work fine, but pin 7 is on all the time. My best guess is that I fried the buffer chip, but that is not where the smoke appeared to have come from... Suggestions (other than not violate the theory of smoke encapsulation)? Does the collective wisdom agree that the buffer/opto-isolator chip is the likely fried? Thanks and best regards, EBo --

You don't happen to have the potentiometer jumper on the input 7 do you? Where'd the smoke come from?

I haven't used the potentiometer thus far, so I did not think so. Maybe it never worked I'll check later... I thought the smoke came from under the CPU or possibly U4 (Op amp buffer 1), but when I saw smoke I was dancing to pull the plug... That's why I started testing things. At this point the basic digital I'O and PWM for the servo's seem to work fine. There is a lot of functionality that I have not checked (such as CAN JTAG and 3.3v signals and output. I've never let the smoke out of something like that and still had it working. nice job on the buffering Cheers. EBo --

We agonized over whether to add the op amps on the input or not. Socketable protection is one advantage, but the best one is the high impedance input... measure anything while hardly influencing it at all.

Well, I purchased replacements for both the input and output buffers/drivers. Now when I read the digital out I get 4.65v (for logical 1) and 0.54v (for logical 0) when powered by the USB port. I seemed to remember, and thought, that the logical 0 value was much closer to 0v than 0.5. What values are other people measuring when powered via the USB? Thanks, EBo --

Well... it finally died and the controller no longer gives me it's little heartbeat. When I pulled the controller off the application board I found one of the chips that fried before -- D1 which is on the bottom of the controller board got so hot it fell off and was floating around... At this point everthing is DOA. Oh well. EBo -