wireless questions

[apc3161]

I was reading through a bunch of threads, such as this one

http://www.societyofrobots.com/robotforum/index.php?topic=104.0

but it seems my questions are still up in the air.

Here are my basic questions, if you guys could guide me in the right direction I'd be grateful

1) Whats the best/easiest method to use UART between a an AVR MCU and a laptop (using a USB port). I just want sensor values to print out to something like hyper terminal.

Any good recommendations for a TTL -> USB conversion? Any hardware you can recommend?

2) Whats the best/easiest way to do the said above wirelessly? Bluetooth, easy radio, what?

3) Whats the best/easiest to program an AVR wirelessly and to communicate values

TTL -> USB -> Bluetooth? -> USB ?

4) Whats the best/easiest way to get to AVR chips to communicate wirelessly. For this one, I only want one AVR chip to send a updating value to another AVR. Example, the voltage that the transmitting AVR is reading on one of its ADC channels.

TTL -> bluetooth? -> TTL

I've read the UART/bluetooth tutorials, but they don't into much detail about hardware it seems. I was hoping some of you will have some experience behind you to answer my questions.

Thanks for any guidance, links that anyone can provide.

-edit

Does anyone have any experiences with using AVR integrated wireless chips?

http://www.atmel.com/products/zigbee/default.asp

http://www.atmel.com/dyn/products/devices.asp?family_id=676

Are they good? I'm trying to decide between using general RF or trying ATMEL's solution. So far I've been really happy with their products.

[SmAsH]

1. you could use a rs232 shifter to make it communicate between your laptops usb and rx/tx lines, alternativly you could just get a usb-serial cable and use a simpler setup.
something like a combination of these two may work: http://www.sparkfun.com/commerce/product_info.php?products_id=133 http://www.sparkfun.com/commerce/product_info.php?products_id=8580
also have a look at wifly...

2. i would suggest two things: bluesmirf or xbee wireless modules, they seem to be the most popular around here.
you could also look into smaller transmitter/receiver pairs.

3. i wouldn't have a clue it may work if you have a serial programmer to put a wireless tx/rx where the cable normally goes?

4. you could use a number of things, such as small infrared led on one end and an appropriate phototransistor on the other end. you could also use more expensive things like bluetooth, xbee etc...

a note to all of the wireless questions, different solutions are for different applications, all of the above will depend on how far you need to transmit (an inch or a mile), what you will be transmitting through (water, open flats, walls, a forest) and how fast you need it to transmit.

[apc3161]

Thanks Smash.

For the wireless distance, I would like to transmit through air up to 100m.

I read that there was a class of bluetooth devices that can go that far. Is bluetooth the cheapest option? All the modules I see cost around $50+. I doubt then that bluetooth is the cheapest option because remote control cars/toys cost less than $50 and are RF controlled...

[SmAsH]

well, definitely take a look at sparkfuns site, there are small pairs like these:
transmitter http://www.sparkfun.com/commerce/product_info.php?products_id=8945
receiver http://www.sparkfun.com/commerce/product_info.php?products_id=8948
that cost very little, under $9 a set that claim 500ft in open space...

the main reason rc cars dont use bluetooth is the simple reason they don't need it! and theres the price factor...
anyway, check here http://www.sparkfun.com/commerce/categories.php?c=16

[apc3161]

Thanks Smash!

So basically, Bluetooth is "overload" for the majority of simple applications? I guess if all I need to do in transmit a single 8 bit number I dont need anything that complicated! So those items you showed can handle simple TTL transmissions? I'm going to go and read more about them now. Thanks

[SmAsH]

yeap, from the description, transmitting that should be fine!
check out this to give you an idea on the setup: http://winavr.scienceprog.com/example-avr-projects/running-tx433-and-rx433-rf-modules-with-avr-microcontrollers.html

[kpmcgurk]

I prefer bluetooth like I have said before... Chicks dig wireless

[apc3161]

Does anyone know, for AVR to AVR communication

Do I have to go from TTL -> serial -> wireless -> serial -> TTL

Or can I just go TTl -> wireless -> TTL?

[apc3161]

Hey SMASH,

On that link you sent me, do you have any idea what those capacitors do in his circuits on the left side of both the transmitter and receiver? I've only seen capacitors in parallel before, when they are used to level out voltage supplies. But I'm not sure what their function in this case is.

[SmAsH]

well, the two that are with the crystal are there because you need them to have with a crystal.
the one next to the switch resistor has something to do with the switch...
i personally don't ever put a capacitor on the reset switch, it just eliminates all the noise....
this thread has more info on it http://www.societyofrobots.com/robotforum/index.php?topic=3903.0

[apc3161]

Does anyone have any experiences with using AVR integrated wireless chips?

http://www.atmel.com/products/zigbee/default.asp

http://www.atmel.com/dyn/products/devices.asp?family_id=676

Are they good? I'm trying to decide between using general RF or trying ATMEL's solution. So far I've been really happy with their products.