Quote:
Originally Posted by geekmaster
Noise on the accessory port is probably caused by voltage fluctuations due to varying load during wifi or 3G transmission (which draws a lot of power), during eink updates, and during other power-hungry events. For PWM output that could be clipped with a resistor and a pair of back-to-back diodes (or LEDs). The ticks might actually be your output. You can time how fast your code runs to see if it matches the tick rate. Like I said, it can take a long time to return from the echo statements, depending on how the device driver handles that sysfs (proc) interface to the accessory port.
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Strange they haven't connected any power stabilizer to the port. They must have known about it when they made it that way. Yes, external lamp does not need it, but... And about that ticks - there are not any output. They appear after enabling power on the port and after that it ticks with interval like 5/sec. Unfortunately, this spoils the attempt to make some data port out of it. I'll try to connect it to the counter to see if it counts that ticks (definitely yes, but to be sure). Then it would be needed to clean them. Not sure if it drops to 0V, but if not, it should be sufficient to move voltage level.