Cheap wireless interface for Pic/AVR? - Page 1
Forum section: electronics / general

author: FenderBender
author_rank: Super Contributor
timestamp: April 25, 2012, 11:03:41 pm
content: Hello,I'm working on designing a simple(ish) RC car and although I'm still in the planning stages, the one thing that really bugs me is the cost of some of these wireless modules. I know Xbee is pretty easy to use but it gets a bit pricey. I remember taking apart an RC car once. I think it had some sort of cheap looking DIP Realtek chip, but now that I think of it... it also had some fancy RF circuitry that only dark magicians can understand.Anyway, it doesn't have to be for Arduino or any of those in particular. I probably won't be using a dev board for the project.But does anyone have any simple and cheap ways to do wireless? I guess a good range would be around 50m. I am fairly certain that Xbee is a one-way street, as in- transmitter and receiver. I was wondering if there is any module that can transmit and receive or use two separate ones if they are cheap enough.Sorry for sounding like a newbie...because I am one, atleast to wireless.Thanks.

author: FenderBender
author_rank: Super Contributor
timestamp: April 25, 2012, 11:32:27 pm
content: Anyone have experience with the Hope RF RFM12 transceiver modules? $7 bucks a pop on Sparkfun.

author: vxp036000
author_rank: Regular Contributor
timestamp: April 25, 2012, 11:50:07 pm
content: It's really not that difficult to homebrew your own transmitter. A simple Colpitt's oscillator and several amplifier stages work like a charm. I'm using this architecture for an ASK transmitter as part of a wireless audio transmitter.Quote from: FenderBender on April 25, 2012, 11:03:41 pm

author: benemorius
author_rank: Regular Contributor
timestamp: April 25, 2012, 11:59:06 pm
content: Quote from: FenderBender on April 25, 2012, 11:32:27 pmI was about to recommend exactly that. I haven't done anything with it beyond checking to see that it would work well with my car alarm transceiver. It's cheap and pretty versatile. For $7 bucks a pop I'd say give it a go if it means getting your project off the ground sooner. They come configured for 433MHz which is ideal for attempting a 50m link without continuous line of sight.

author: FenderBender
author_rank: Super Contributor
timestamp: April 26, 2012, 12:17:09 am
content: Quote from: vxp036000 on April 25, 2012, 11:50:07 pmWould this work for digital transmission? It would seem that it might work fine with analog, just not sure of reliability with digital packets.Am I wrong about this? I definitely could be.

author: FenderBender
author_rank: Super Contributor
timestamp: April 26, 2012, 12:20:48 am
content: Quote from: benemorius on April 25, 2012, 11:59:06 pmPerhaps I will give it a try. I'm still in the beginning stages so I don't know what I will be thinking later, but the RFM seems easy enough to figure out. I haven't looked at it in depth though.

author: jgmcc
author_rank: Newbie
timestamp: April 26, 2012, 01:12:46 am
content: I like the Nordic Semiconductor nRF24L01+ series. It's a 2.4Ghz packet radio with a SPI interface. Sparkfun has $20 chip antenna and SMA breakout boards, and a $36 USB to SMA version to connect to a PC.Cheers, John McC.

author: jpelczar
author_rank: Contributor
timestamp: April 26, 2012, 10:25:27 am
content: You can use e.g. the CC1000 wireless modules (working at 433MHz and several others), but this will require to port the driver and add some extra code for detecting the transmission/preparing packet to send. You could also use for example BTM331 Bluetooth module (or any other) - they usually supply the serial interface which you can hook directly to the microcontroller. Depending on the range you'd want to use.You could also probably add basic radio transmitter/receiver and handle FSK in software.

author: FenderBender
author_rank: Super Contributor
timestamp: April 26, 2012, 08:21:49 pm
content: Quote from: jpelczar on April 26, 2012, 10:25:27 amThat one also looks pretty decent. Still better than Xbee IMO. Not sure how Xbee got so popular tbh.

author: westfw
author_rank: Super Contributor
timestamp: April 26, 2012, 10:16:11 pm
content: >> homebrew your own transmitter.You may want to pay attention to legal issues. In theory, a pre-built module has passed appropriate RF-related certifications. (Though it's hard to say with those very inexpensive imports.) Whatever you homebrew will not have passed. On the third hand, even a homebrew is unlikely to fail so badly as to attract attention.