| hauptuhrDotNet | Posted: 8 Apr 2018, 06:17 AM |
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 Member Posts: 1 Joined: 6-March 18 |
Hi, I've been very keen to build the Morse Code USB Keyboard Mk II so today I had a crack at it. I have run into a problem which I describe further below. Firstly, I am new to Atmel chips. I began today by getting the Hello World flashing LED working. Once that worked I set the low fuse to c1 as the instructions stated and then I successfully burnt the chip with the HEX file published on the project page. I used AVRdude. I have double and triple checked the wiring and found only one mistake which when corrected did not solve the problem. The one change I made to the published design was to leave out the Piezo. The device is recognised in Windows XP. Initially it comes up in the Device Manager as "Morse Key" with a " ! " icon but then quickly changes to a HID device, which it says is functioning properly and has been correctly installed. When I close the morse key (ground PB4) however, the "device removed" sound plays and the device disappears from Device Manager. This is as though I had removed it from the USB port. I can not get it to recognise the device again unless I change to a different USB port. I am able to change back to the original USB port and it appears again in the Device Manager. I am not able to 'type' any text. As soon as I close the key, the device disconnects. I measured the voltage at VCC with the key open and then closed and there is no voltage drop. I have not measured current draw. When I measure the voltage at PB4/Pin 3 (the key input pin) it reads 5V. However, once I close the key just once and then release it, the voltage at PB4/Pin 3 only gets back up to 0.12V and the device removed sound plays. The voltage at PB4/Pin 3 does not return to 5V until I change to a different USB port. I noticed some differences in component values between the circuit diagram and the photos of the finished product. Does anyone have any thoughts on the next step I should take to track down the issue? Cheers, Nick ------------- |
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| mit | Posted: 8 Apr 2018, 04:27 PM |
 yeah whatever Admin Posts: 538 Joined: 4-May 16 |
That's really strange. My first reaction is that there must be a wiring problem. Maybe the ground isn't connected properly, and it's using something else as the return path? Then when the key is shorted to it, it could be disrupting that... although, the PB4 pin should only be a weak pullup. The differences in part numbers probably doesn't matter, I think I used 100ohm resistors instead of 68 but that shouldn't make a difference. I'm wondering if there's a problem with the hex file I uploaded... hopefully not, I know that several people have built their own versions of this, but they might have all re-compiled the program, I'll double check it. I don't think I put the link on that page, but I did later upload the full source code to github here. edit: looking at the schematic, I think the 33uF is probably pointless, a 1uF should be fine. Sometimes having a power capacitor that's too big can cause inrush problems... but if that were happening, it wouldn't get as far as saying "morse key". Last edit by mit at 8 Apr 2018, 04:36 PM ------------- |
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| mit | Posted: 8 Apr 2018, 04:58 PM |
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yeah whatever Admin Posts: 538 Joined: 4-May 16 |
Well, OK, this is embarrassing. The hex file that's linked to on the project page might be corrupted. But I just tried out the hex file that I left on the github page, and it worked, so give that one a go. I'll update the link on the project page in a moment. ------------- |
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