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Communicating with rs232


i recently purchased a wixel to control a cameras higher functions, have trie various terminal apps, and still nothing, any help would be great


Hello, infraredtech.

Did you visit us yesterday? Have you tried using the Wixel’s USB-to-Serial App in conjunction with the Pololu Serial Transmitter as I suggested?

We want to help, but your first post doesn’t contain enough details for anyone to actually help. Please read Read Before You Post: General Advice for Getting Help.




Please note that RS-232 is a protocol that involves/specifies +/-12V signals. The Wixel can absolutely not handle these voltage levels.

- Ryan


David - Yes, we have done what you recommended us doing and we get some HEX code bad back from the camera, but it is not doing what we want it to do. The camera is in working order and nothing is wrong with the camera and we know that for a fact. We have all of our connection connected properly, we have gone through and checked them over like 10 times and we know that those are correct. We just don’t understand why the USB-to-Serial in conjuction with the Pololu Serial Transmitter is not getting the desired results that we need.

Ryan - “The camera is capable of being controlled remotely through an asynchronous serial interface consisting of the signals named RX, TX and GND using 3.3 volt signal levels” that is directly from our cameras user manual.

flir.com/uploadedFiles/Tau_3 … 110607.pdf

that is the user manual for this camera. In it has all the HEX function codes to make it do higher function but we are unable to get them to work.

We have checked all of our Serial Port Settings and have made sure that is all correct and it is by default.

now if we bring in the camera and everything we have or would need is there someone that can sit down with us for a little while to help us work on this and make it at least do one thing!


Hello, infraredtech.

There is a note in section B.1 of the camera’s user’s guide that says:

Unforunately, RS-232 uses inverted serial (high voltage means 0) but the Wixel only supports doing non-inverted serial. Unfortunately I did not notice that note yesterday, but I did tell you at a late stage that we hadn’t confirmed whether the camera uses inverted or non-inverted serial and this could be an issue. I wish I had warned you more clearly that this might be an issue.

I think that to make the Wixel work with this camera, you will need some way of inverting the signals. You need a circuit that outputs 3.3 V when given an input of 0 V and outputs 0 V when given an input of 3.3 V. You need two of them in order to do bidirectional communication. You can make such an inverter using a MOSFET and a pull-up resistor. We have two MOSFETs built into the Wixel Shield that you could use to make the inverters. Alternatively you could get an IC that has 2 or more inverters in it, such as this part from digikey:
I think that IC would work for you but I haven’t read the datasheet thoroughly enough to be absolutely sure.

You said you have an Arduino Uno. The NewSoftSerial library for the Arduino supports inversion, so you could try to use that to communicate with the camera. Please remember that unless you find out that the camera’s RX line can tolerate 5 V, you will need to have a voltage divider between the Arduino’s TX line and the camera’s RX line.

I think you should bring all your stuff in to LVBots next Thursday. If it’s working by then, you can show us what you’ve done. If it’s not working, we can probably help you figure out what is going wrong.



can you give us a diagram for the wixel shield, we have the wixel sheild but dont know where the MOSFETs are on it.



From the very top of the “Read before you post” thread that David linked to you in his first response to you:

Have you tried looking at the product web page for the Wixel Shield?

- Ben


yes, we have looked at the wixel shield webpage and looked under the resources and was unable to find a diagram that will show us how to invert the serial with the wixel.


You’re shifting the goal posts here. Your original statement amounted to “we can’t find the MOSFETs; do you have a diagram of the Wixel?” This is definitely covered in the user’s guide:


Now you’re acting as if you were asking for a more specific diagram of how to invert serial signals. You would basically want to connect your camera’s serial output to one of the MOSFET circuit LV pins and connect the corresponding HV pin to your Wixel’s serial input. Similarly, you would connect your Wixel serial output to the LV pin of the other MOSFET circuit and the corresponding HV pin to the serial input of your camera. You probably also need an external pull-up on this HV pin.

- Ben


is there a diagram, to invert the signal out?


I do not have a complete diagram to give you. Can you tell me what part of my previous post is unclear? If you try to draw up a diagram based on the connections I described, I can tell you if it looks correct.

- Ben


according to the docs on the wixel, it already output an inverted signal, so which is it, inverted or non inverted?
the camera im trying to talk to, requires inverted


I just checked the Wixel User’s Guide and there is no place where we say that the serial data lines are inverted. They are non-inverted. Could you provide a link to the sentence that made you think the serial data lines are inverted? Remember that in our apps the control lines like DTR and RTS can be inverted, but those are not the same as the serial data lines (TX and RX).



I cant find it now, my mistake David, been reading so much, trying to get this to work, thanks for your help