Serial output not seen

Support forum for the mightyohm.com Geiger Counter.
http://mightyohm.com/geiger
Post Reply
rvh
Posts: 4
Joined: Sat Nov 12, 2011 12:25 am

Serial output not seen

Post by rvh »

I had a lot of fun building the kit and everything seems to be working normally except for the serial output. Does anyone see any reason why the cable linked below wouldn't work with the unit?

http://www.serialstuff.com/products/USB ... eader.html

I've tried swapping the tx and rx lines with no effect. I'm fairly new to this stuff so I imagine I'm missing something fairly obvious. Any help would be appreciated.

Edit: I did a loopback test with the cable and it echos back what I type to the terminal just fine, so there's that.
User avatar
mightyohm
Site Admin
Posts: 1064
Joined: Fri Apr 03, 2009 10:29 pm
Location: Seattle, WA
Contact:

Re: Serial output not seen

Post by mightyohm »

Have you checked to see if the pinout of your cable matches the FTDI cable?
rvh
Posts: 4
Joined: Sat Nov 12, 2011 12:25 am

Re: Serial output not seen

Post by rvh »

The site gives this as the pinout:

Pin 1 GND
Pin 2 CTS
Pin 3 VCC
Pin 4 TXD
Pin 5 RXD
Pin 6 RTS

which looks correct to me. The cable colors also seem to match the pinouts.
User avatar
mightyohm
Site Admin
Posts: 1064
Joined: Fri Apr 03, 2009 10:29 pm
Location: Seattle, WA
Contact:

Re: Serial output not seen

Post by mightyohm »

The pinout looks ok. Make sure you plug the connector in with the black wire closest to the "blk" label on the PCB.

Are you setting yout serial terminal to 9600 baud, 8N1?

Are your batteries fresh? Some USB-serial converters might be less tolerant of low voltage levels than the FTDI cable is.

Have you double-checked that the serial connector pins are all soldered well and there are no shorts between them?
rvh
Posts: 4
Joined: Sat Nov 12, 2011 12:25 am

Re: Serial output not seen

Post by rvh »

Solder joints are good, confirmed all the way up to the IC socket. Two sets of batteries tried with same result. Terminal settings confirmed on two platforms (win, linux).

The only thing I can think of is that this FTDI cable is somehow not to standard even though it uses the same chip and design. As a last resort, I have ordered the cable that most people seem to be having success with.
User avatar
mightyohm
Site Admin
Posts: 1064
Joined: Fri Apr 03, 2009 10:29 pm
Location: Seattle, WA
Contact:

Re: Serial output not seen

Post by mightyohm »

The FTDI cable will certainly help us troubleshoot the problem. Sorry you're having so much trouble with the serial connection. Please post again when you get the FTDI 3.3V cable and let us know if that fixes things.
rvh
Posts: 4
Joined: Sat Nov 12, 2011 12:25 am

Re: Serial output not seen

Post by rvh »

The replacement FTDI cable from sparkfun worked immediately. I can only guess that the other cable must have been mislabeled upon shipping as a 3.3v version when it is actually 5v. Thanks for your guidance and patience.
User avatar
mightyohm
Site Admin
Posts: 1064
Joined: Fri Apr 03, 2009 10:29 pm
Location: Seattle, WA
Contact:

Re: Serial output not seen

Post by mightyohm »

This is good information, I'll have to add "use a genuine FTDI cable" to the instructions.

Thanks for sharing the fix.
Post Reply