2SIO silkscreen error

[TomL_12953]

Originally Posted by Geoff Harrison

If you're building one of Grant's 2SIO boards, be aware that the silkscreen is incorrect for D3, D6, D9, D12, D15 & D18. The cathode should be up toward the Molex connectors, instead of down as shown on the silkscreen.

This matters only if you are configuring the board for a current loop device, those diodes are not used if you are configuring it for RS232.

Geoff.

Does this mean my TTY would've worked???

Tom L

[Geoff Harrison]

Originally Posted by TomL_12953

Does this mean my TTY would've worked???

Tom L

Well, with the diodes installed as per the silkscreen, no input signals were getting through to the UART. After I rotated them, the input was getting through,

but...

the pulses arriving at the UART are very messy (see the scope trace below) and I'm not sure why. The UART can't handle it. I'll play with it a while longer, but I think it makes most sense to convert it to RS232. As you said elsewhere, it will make for a more versatile interface.




The bottom trace is the input to IC K pin 9, which is supposed to be more or less TTL, the top trace is the output from IC K pin 8, which should be a clean TTL square wave.

Geoff.

[TomL_12953]

Originally Posted by Geoff Harrison

The bottom trace is the input to IC K pin 9, which is supposed to be more or less TTL, the top trace is the output from IC K pin 8, which should be a clean TTL square wave.

Geoff.

So could IC K be bad?

Tom

[Geoff Harrison]

Originally Posted by TomL_12953

So could IC K be bad?

Tom

I changed it just to be sure, but that's not it. The problem is that the incoming data stream, after being converted from current loop to TTL voltage swings is not clean enough to drive the 7404 inverter properly. For all I know it may be a problem with the current loop/RS232 adapter I'm using to drive the board.

Did you verify that you can drive your asr33 with your adapter correctly? If so, then switching the 2SIO port to RS232 should get you up and running.

Geoff.

[TomL_12953]

Originally Posted by Geoff Harrison

Did you verify that you can drive your asr33 with your adapter correctly? If so, then switching the 2SIO port to RS232 should get you up and running.

Geoff.

Yes. I was running the TTY on port 2 with my converter sucessfully so if you could just change port 1 to RS-232 (still 110 baud of course!) I'd be all set.

Thanks!
Tom