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tuzzer
09-26-2009, 05:17 PM
On the rule and guideline of Mech Warfare. It said that we should use Wifi camera because RF camera won't work in such noisy environment. Then what about remote control? Should we use those that use RF?
Would something like this work? http://www.trossenrobotics.com/bioloid-zigbee-wireless-module-set.aspx

If not, does anyone have any recommandation?


Thanks!


matthew

Adrenalynn
09-26-2009, 05:23 PM
Zigbee/Xbee is similar to WiFi in that it's a much more robust band. That said - some even had apparent issues with their XBee - which is pretty rare.

tuzzer
09-26-2009, 05:26 PM
Zigbee/Xbee is similar to WiFi in that it's a much more robust band. That said - some even had apparent issues with their XBee - which is pretty rare.


It is similar to Wifi? What is that make this RF connection more robust??


Matthew

lnxfergy
09-26-2009, 06:52 PM
Any wireless link is going to loose some data -- it's how you handle the losses that decides your outcome. A solid packet structure is essential. The first task is to create a coding scheme using a checksum. Those zigbee units you pointed out do just this, for every byte of data you want to transfer, it sends the original byte + a checksum byte (which is just ~byte). After applying a checksum, you'll be able to know if a packet is corrupted, there are then 2 schools of thought here:


Send data only when it updates, but implement a handshake so that you know that data got through. This is essential if you have to transmit your entire pose or whatnot (an implementation I would not recommend).
Send all parameters in every transmission, and send it frequently. This avoids handshaking of any kind (which can speed stuff up a bunch, and simplify code). Issy took this approach, a frame of data was sent 30 times per second, each frame containing the forward walking speed, turning speed, gun tilt position, and gun status (fire or no-fire). If a packet got corrupted, he just dropped it, as even if we lost 2/3 of our packets, we'd have something around a 10hz update rate -- more than enough for a mech.

EDIT: unless you are using those bioloid zigbee radios with a BIOLOID kit, I'd suggest avoiding them. They have some special stuff for the bioloid CM-5, and you'd be much better off with a regular XBEE radio.

-Fergs

tuzzer
09-26-2009, 08:09 PM
Thanks for your explanation.
I chose this because the XBee wireless module in here (http://www.trossenrobotics.com/c/xbee-zigbee-wireless-robotics.aspx) doesn't work with TTL. I will be having it to talk with a dsPIC33F. The ZigBee one seems like it can be easily hooked up to the PIC serially. I am actually new to this, not sure how this would work. But the XBee ones has the weird interface that I am not familiar with, while the ZigBee one has like TxD and RxD. It would be great if you can let me know which wireless module can give me the easiest time if I will have a PIC talking to a computer (planning to use a RS-232 to TTL converter on the computer side)


Matthew

jes1510
09-26-2009, 08:35 PM
Assuming your PIC is 5v then this will work connecting to the PIC:
http://www.trossenrobotics.com/store/p/5977-XBee-Explorer-Regulated.aspx

This board will let you connect the XBEE to a compuer via USB:
http://www.trossenrobotics.com/store/p/5828-XBee-Explorer-USB.aspx

Note that neither of the above boards come with the XBEE's. If you want a complete kit this this should probably work:
http://www.trossenrobotics.com/p/Xbee-Communication-Starter-Kit.aspx

lnxfergy
09-26-2009, 09:26 PM
Thanks for your explanation.
I chose this because the XBee wireless module in here (http://www.trossenrobotics.com/c/xbee-zigbee-wireless-robotics.aspx) doesn't work with TTL. I will be having it to talk with a dsPIC33F. The ZigBee one seems like it can be easily hooked up to the PIC serially. I am actually new to this, not sure how this would work. But the XBee ones has the weird interface that I am not familiar with, while the ZigBee one has like TxD and RxD. It would be great if you can let me know which wireless module can give me the easiest time if I will have a PIC talking to a computer (planning to use a RS-232 to TTL converter on the computer side)

XBEE modules are just 3.3V RX/TX serial. All you need is a 3.3V->5V converter to do TTL (Although as most of us have found, while not recommended by Digi, the regular series 1 XBEE devices work fine with TTL serial)

-Fergs

tuzzer
09-26-2009, 09:31 PM
XBEE modules are just 3.3V RX/TX serial. All you need is a 3.3V->5V converter to do TTL (Although as most of us have found, while not recommended by Digi, the XBEE devices work fine with TTL serial)

-Fergs


Hi Fergs,


I use dsPIC33F which is 3.3V already.
And if I am using the Xbee wireless module (http://www.trossenrobotics.com/store/p/5827-Xbee-Pro-60mW-with-Wire-Antenna.aspx), how do I interface it with my PIC?
Don't I need an adapter of some sort?
Thanks... (I am jsut starting to be more familiar with how serial in PIC works)

Matthew

Adrenalynn
09-26-2009, 09:34 PM
As memory serves - pin 2 is tx on the XBee and needs to go to rx on your mc. pin 3 is rx on the XBee and goes to TX on your mc. VCC is pin 1, 10 is GND. From there, it's just like a serial cable.