wtf electronics
Alright, so I build this circuit up on a breadboard, get it all functional and stuff- translate it directly to a pcb and the thing behaves oddly and doesn't work.
I know I've done something wrong, but the design isn't that unstable that I'd expect it to completely crap out.
I'm perplexed.
This is the circuit in question.
On the left, it plugs to the car, open collector NPN. On the right it connects to an Arduino Uno R3, with the UART input pulled high internally from a 2k2 resistor, and brought down by the right hand NPN, acting as an open collector.
It is used to transmit a serial data stream at 62500 baud.
Hooked up it translates the output of my waveform generator making a square wave perfectly.
That's the trace at the uart pin, 1V/div vert, 50uS/div horz.
It's driving me crazy. The breadboard setup worked, this one... it doesn't even recognise any data unless I put my finger onto the collector pin of the 2N222A, and then it's scrambled.
Failure bites.
I know I've done something wrong, but the design isn't that unstable that I'd expect it to completely crap out.
I'm perplexed.
This is the circuit in question.
On the left, it plugs to the car, open collector NPN. On the right it connects to an Arduino Uno R3, with the UART input pulled high internally from a 2k2 resistor, and brought down by the right hand NPN, acting as an open collector.
It is used to transmit a serial data stream at 62500 baud.
Hooked up it translates the output of my waveform generator making a square wave perfectly.
That's the trace at the uart pin, 1V/div vert, 50uS/div horz.
It's driving me crazy. The breadboard setup worked, this one... it doesn't even recognise any data unless I put my finger onto the collector pin of the 2N222A, and then it's scrambled.
Failure bites.