Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: Sensor Guy on May 11, 2010, 09:51:41 PM

Title: Axon II and SDI-12
Post by: Sensor Guy on May 11, 2010, 09:51:41 PM
Would the Axon II be able to work with SDI-12 products
(SDI-12 stands for serial data interface at 1200 baud. It is a standard to interface battery powered data recorders with micro-processor based sensors designed for environmental data acquisition)
Title: Re: Axon II and SDI-12
Post by: Admin on May 11, 2010, 10:18:55 PM
Yeap, just use the UART and set it to the desired baud. Sending out data requires a single line of code with WebbotLib.

Receiving data will require a bit more thought, but there are lots of examples available.
Title: Re: Axon II and SDI-12
Post by: Sensor Guy on May 14, 2010, 10:52:29 AM
Hi;

Would I still need a level shifter with the SDI-12?
also when using the UART (serial), do I need a level shifter for each?

Thank you
Title: Re: Axon II and SDI-12
Post by: GearMotion on May 14, 2010, 11:04:44 AM
Hi;

Would I still need a level shifter with the SDI-12?
also when using the UART (serial), do I need a level shifter for each?

Thank you

SDI-12 uses a single bi-directional data line that runs at 5V. You certainly would not want to use an RS-232-type level shifter. If the micro runs at 3.3V, you would need to shift the levels to 5V.
Title: Re: Axon II and SDI-12
Post by: Sensor Guy on May 14, 2010, 11:15:10 AM
Would it make any difference that the sensors on the SDI-12 are 3.6V?
Title: Re: Axon II and SDI-12
Post by: GearMotion on May 14, 2010, 11:22:36 AM
Would it make any difference that the sensors on the SDI-12 are 3.6V?

Interesting. I knew of SDI-12 as having a 5V data line - the spec then refers to 3.5V as the threshold for high. But I understood the sensors to run on 12V.

That is the nice thing about standards. There are so many to pick from. :LOL:


Title: Re: Axon II and SDI-12
Post by: Admin on May 14, 2010, 11:26:33 AM
The Axon has protection resisters on the UART lines, so in theory it should be fine. I operate the 3.3V Blackfin camera with the Axon all the time no problem.

But if you don't want to risk it, you should use a level shifter on the Tx line of the 5V device.