Laser Range finder on Roboard RB100

[ading12 offline]

Hi,

I have the RoBoard RB100 and was trying to interface the laser range finder from parallax to it but to no avail.
Currently I have Lubuntu installed on the micro SD, and done all the setup procedures as posted on the Roboard website. I also have an ultrasonic range finder connected to COM1 of the roboard and it works. I can read the values from the sensor.

But when I tried using COM3 on the board, as it is TTL same as the laser range finder, it didnt do anything. (tested on cutecom).
I would really appreciate if anyone could suggest anything i could do to fix this.

[limor]

have you managed to interface with any other computer ?

[ading12 offline]

have you managed to interface with any other computer ?

I have tested it with an arduino uno and it worked.

[PedroR]

Hi Adding

On certain Linux distros you'll need some additional procedures to enable COM3 and COM4.

Please refer to one of these links depending on your Distribution:

http://www.roboard.com/Files/RB-100/Ins ... oBoard.zip
http://www.roboard.com/Files/RB-100/Ins ... oBoard.zip


In the Zip file you'll find instructions about enabling Com3 and COM4.

Regards
Pedro

[ading12 offline]

Hi PedroR

I have enabled them and i tested that they indeed are enabled. I connected rx to tx on com3 and what i send was received. But when i tried using the laser range finder it did not seem to work. help

[PedroR]

If COM3 and COM4 are enabled then it's most likely an issue with the signal levels between the two boards.

I believe the signal level on Roboard is 5V TTL.

I'd recommend that you check the following:
1) Check if your Ultrasonic range finder is outputting TTL at 5V or at 3.3V

If it's outputting at 3.3V you'll probably need to use a logic level converter (see here http://robosavvy.com/store/logic+level ) to boost the signal to 5V on arrival at the Robot.

What happens most of the times is that 5V systems can't always see incoming data when it's at 3.3V.

Arduino's can cope with this very well but I believe Roboard doesn't. You should make sure the signal levels match.


If you have access to an oscilloscope you should be able to analyse the input/output levels on the serial port on Roboard and compare them to what's going on with the serial on Arduino.


2) Make sure you have the baud rate and handshake settings all set correctly.
This is a bit obvious but it's a good idea to double check.


Pedro.

[ading12 offline]

These are what I had done so far.

1) Check the signals of the COM3 port on the roboard using oscilloscope. I cant remember the voltages but it is lower than the laser range finder signals.

2) connect using the level converter. still no response

3) using a USB to TTL cable to connect the COM3 port to another computer. with both running cutecom, I can communicate between the two. I even tested with the level converter between the two and it still work.

4) also using the USB to TTL cable to connect the laser range finder to the computer. This also works.

Am I missing something here.

[PedroR]

Hi Adding

To be honest I'm also out of suggestions here.

You've established:
1) Roboard is able to communicate with other devices

2) The Rangefinder is also able to communicate with other devices.

They just don't talk to each other.

My only suggestion here would be to use an oscilloscope or a logic analyses to see what's happening there.

It's most likely something related to the signals (or something so obvious it's being overlooked - which can be quite frustrating I might add from experience).

Kind Regards
Pedro.

[ading12 offline]

Hi PedroR

Ive finally figured out the problem. Indeed it was something being overlooked. It turns out I have to change permission to the ports so that I can actually read and write from the port. A friend helped me debug and now it works even without the level converter. Obviously i need to learn more on linux. Thank you for helping me out.