SDC2130 TTL Serial Communication

Do you have an oscilloscope that you can use on the TTL lines to see if any activity is being seen on the TTL lines?

Yes. I mentioned this above actually.

I have a Tektronix TBS 1022 Digital Storage OScope. A fully featured scope.

I can capture bytes on the RS232 lines, but can't get anything at all on the TTL lines. They are a constant 3.3 V with no serial activity.

Again: RS232 pins have activity I can capture. TTL pins: nada.

Are these pins normally operative on SDC2130?

Sorry about that.

They should be operative. Let me see if I can find any other information that might help.

Just to confirm... RS232 and TTL share the same ground pins, and the two ground pins are tied together?

I've tried my scope grounding probe on both ground pins. I've tried TTL Tx and Rx with the + probe. (Both are the same 3.3V steady).

I've tried both falling and rising edge triggers. (I assume it's falling since it's inverted TTL.)

Yes, the grounds on the controller are all internally connected.

Sanity Check:

I set the Roboteq aside for a moment, and connected my serial display to my PC via an RS232/TTL converter board.

I wanted to see if I could capture the TTL signal with my scope, which I was able to do easily when I sent the display a command byte.

Now back to the Roboteq!

Try using a hyper terminal program and connect that to the ttl lines. The hyper terminal should also display the FID uponpower up and connection.

If your oscilloscope is connected to the TTL output, you should see the signal on the line when the controller powers up as it sends the ?trn and ?fid.

I've connected my PC to the TTL pins via my RS232/TTL converter.

I used RealTerm, which I have on my W7 machine.

Each time I reboot, I do get the "FID=Roboteq v1.3 RCB100 03/11/2014" along with a variety of stray garbage, perhaps from noise on the line? I get the FID once, and it is the only thing readable.

I've tried sending commands such as ^RWD 0 or ?FID but I get no response.

So it looks like the TTL is working, but the data received isn't coming in clean.


115200 bits/s
8-bit data
1 Start bit
1 Stop bit
No Parity
No flow control

I downloaded and installed the same software.

To get it to work via serial I had to set the following.

Under display tab,

display as ascii.
Half duplex


Under port

115200 bits/s
8-bit data
1 Start bit
1 Stop bit
No Parity
No flow control

See screenshot of my results.

I don't have anything on hand for the TTL yet.