cvoinescu wrote:USB is fine for small devices, but stuff with big power supplies causes problems. To me, this seems to be caused by ground problems more than anything else. Other systems either have galvanic separation (Ethernet), have very high noise immunity (RS232) or are much more tolerant to common mode noise (RS485). I've managed to get continuous uninterrupted prints via USB by using optoisolators. It is possible to isolate USB itself, but it's much cheaper to isolate the TTL-level serial signals between the USB-to-serial adapter and the microcontroller. I connected a cheap USB-to-TTL-serial adapter to two 6N137 optocouplers, with no electrical connections between the USB and the rest of the printer. That completely eliminated my random interruptions. I used an Arduino, which has resistors between its on-board USB-to-serial adapter and the respective pins, so an external adapter overrides the on-board one. I'm not sure what the situation is on the Azteeg; worst case, you may have to cut a trace.
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