I am interested in getting some wireless networks working for remotely controlling a robot w/ arduino from another arduino. Before you say Xbees, I have a mac and therefore can't config them.
I'm not really interested in extreme speed, but I want something that is cheap and easy to use. Any suggestions?
Well, the vast majority of xBee configuration can be done with just a terminal program, so you can do almost everything you'd need on a Mac. Only thing you need a PC for is to install the firmware onto the xBee in the 1st place, so if you can occasionally borrow a friend's PC, you should be ok.
That being said, here's a good summary of what's out there:
But Xbees will be overkill. Some of them have a freakin' 1 MILE range! I'm talking about ~20ft maximum. Do the General TX/RX (from sparkfun, cheap) work well if I use the virtual wire library?
Thanks!
Do the General TX/RX (from sparkfun, cheap)
If you mean the ones I think you mean, I don't think they can do what I think you think they can.
The JeeNode uses this. Has anyone used it? Is it easy to use/reliable? It is smd, but the pin spacing is 2mm.
Thanks!
I've used these cheap RFs successfully.
RF Link Transmitter - 434MHz
http://proto-pic.co.uk/products/RF-Link-Transmitter-%252d-434MHz.html
The VirtualWire library makes programming it easy.
http://www.open.com.au/mikem/arduino/
The simple TXRX pairs work in line with what you pay for them, the virtualwire library is a software fudge to get around some of the issues with such primitive radio gear (in theory it should work with plain old serial). Theres no error detection/correction as there there is with the bluetooth/wifi based kit, you write it yourself and live with the limitations.
But all I want to do is to send two integers- joystick y axis and joystick x axis. I should be able to send this with good enough speed and reliability as there is no noticeable errors or lag, right?
I ran mine at 1000 bits / second to get the errors down. It worked but it wasn't fast. I used a checksum system for error detecting and ignored the stuff that didn't pass the checksum. Its one way only, so you need a pair to get a back channel. I would have doubts about running a TX and RX together on similar frequencies in close proximity. Its crude ASK modulation which is just on/off keying, the limitations of the simple AGC on the receiver is what the virtualwire library is supposed to help out with.
If one way and two values will do, its probably worth a stab for the low cost.
You're probably limited to checksums as error detection and there is no back channel to request a resend.
Just don't expect too much
What about the Hope RFM12 or 22 modules? are those any good? There only $2 or $3 more expensive.
And I don't need 2-way: just sending 8 bit integers in 1 direction.
No direct experience with them, but FSK has to be an improvement on ASK. Its still just on/off keying though.
What would you do for single direction, cheap RF?
I used mine to avoid the need to run wires on a fixed installation, I abandoned wireless and just ran a cable in the end. I suspect the Hope kit using FSK would work better than the cheap ASK type, due to the AGC situation with FM modulation rather than AM, I reckon using the virtualwire library wouldn't give you any advantages over straight serial. I'd certainly look at it. FM/FSK is much less prone to interference than AM/ASK.
Or how about a nordic module such as this one? They are as expensive as xbee's, but you need minimal supporting hardware.
I haven't tried these... but if price is the problem, these are around eBay for almost half the price of the XBees...