Wireless RF module - Bit bashing

[Spadez]

Hi,

I need a RF module for my project and ive been trying to find ones which are simple to use and code in assembly. Ive been told to look for ones that use "bit bashing" and have a two line connection, one for data and one to "clock in" the data (i.e tell it when to look at the data line).

Ive tried searching for RF bit bashing and other relevant terms but havent had any luck. Would anyone be kind of enough to recommend a RF module that also make it as easy as possible to achieve wireless communication?

Thank you!

James

P.S The range doesnt need to be more than 20M

 

[magnatro]

a simple rf module if 434 mhz will do it

 

[Nigel Goodwin]

Check out my PIC RF tutorial.

 

[Spadez]

I can only see I2C RF tutorials on your site. Ive been told these are more difficult that bit bashing RF modules.

Magnatro, ill look at 434Hz designs.

 

[Spadez]

This one seems really good. Can I get your opinion please?

SparkFun Electronics - RF Link Transmitter - 434MHz

 

[bee]

Spadez
I have done a project with similar Transmitters an Recievers and they work well
They are fairly cheap so give them a go
Nigels tutorial no 12 was invaluable for me "licence free modules"

cheers
Bernie

 

[DirtyLude]

Don't bother with those ancient RF link modules. They are terrible. The RFM12B's or out of stock on Sparkfun, but the RFM22's are in stock. For only a tiny bit more than a transmitter/receiver pair in those basic RF modules the RFM22 transceiver does full encoding and queuing for you. You can talk to it over SPI, which is simple to "bit bang".
SparkFun Electronics - RFM22-S2 SMD Wireless Transceiver

If you didn't mind doing a bit of simple encoding, I would say save your money and get the RFM12B's, which is a full transceiver cheaper than a transmitter/receiver pair. It just doesn't have encoding built in like the RFM22.
SparkFun Electronics - RFM12B-S2 Wireless Transceiver

The only problem here is that it sounds like you are really a beginner and though it's pretty basic you'd actually have to do some research to get this going.

 

[Spadez]

Hi.

Damn I already brought that first one, is it really that aweful? It was only 8 pounds anyway.

How difficult is it likely to be for me to get this rfm22 module working? Is this the easiest and smiliest way to create a reliable wireless data connection.

 

[DirtyLude]

I have no idea what your level of experience is, so I can't tell you how easy it would be. You would need to interface with it using SPI, which can be done with a hardware block, or it's simple enough to bit bang. There is an IRQ pin that tells you when data is received or ready to send, but it's a nice to have rather than a need to have as you can always poll the module to find out if there's data waiting. I do not have experience with the RFM22, just the RFM12B, but more stuff is done for you on the RFM22. You'll need to send some setup info to the module at the start and it should be as much as sending your data. It automatically packets it up for you and encodes it, but you still need to send the preamble.

HopeRF gives some sample code to use it and I'm sure if you googled around for it, you could find some info from other users.

 

[bee]

Spadez

What are you trying to control with these things

Bernie

 

[Nigel Goodwin]

I can only see I2C RF tutorials on your site. Ive been told these are more difficult that bit bashing RF modules.

Magnatro, ill look at 434Hz designs.

No, my RF tutorial is fully 'bit bashing', and certainly isn't I2C - I suspect your definition of what you imagine 'bit bashing' is, is actually incorrect?.

My tutorial uses software for Manchester coding, if you want an easier method you need to buy modules (more expensive ones) that provide this on-board, but in that case you don't need 'bit bashing' as you just need a standard serial connection and can use the UART.

 

[Spadez]

Im litterally just trying to do three things.

Unit one controls a pump with a temp sensor. Unit two has an LCD and speaker and two switches.

Im trying to send the temperature from unit one to unit two so I can display it on the LCD. I also want unit one to be able to tell unit two when to turn the speaker on. Finally unit two needs to be able to send a signal to unit one to turn the pump on.

Im not even sure what SPI is so I will need to look into that. Ive also been recommended this module:

SparkFun Electronics - Transceiver nRF24L01+ Module with Chip Antenna

 

[Nigel Goodwin]

Im litterally just trying to do three things.

Unit one controls a pump with a temp sensor. Unit two has an LCD and speaker and two switches.

Im trying to send the temperature from unit one to unit two so I can display it on the LCD. I also want unit one to be able to tell unit two when to turn the speaker on. Finally unit two needs to be able to send a signal to unit one to turn the pump on.

Im not even sure what SPI is so I will need to look into that. Ive also been recommended this module:

SparkFun Electronics - Transceiver nRF24L01+ Module with Chip Antenna

Looks like massive overkill for what you want, but should do the job fine.

 

[Spadez]

Hi.

Im sorry for pushing my luck here but im narrowing it down with your help. Here is my last issue:

My teacher has used this module before:
RoboSavvy UK - Store

It also has a little bit of example ASM code on the website that will help with the coding side of things. The issue is that it runs off 3.3V and everything else runs off 5V. This means I need a logic converter and another voltage regulator, which is just more things to go wrong.

However, sparkfun also do this module:
SparkFun Electronics - Transceiver nRF24L01+ Module with Chip Antenna

This looks exactly the same and seems to have the same components apart from added voltage regulators, allowing it to receive 5V PSU and signal. However it doesnt come with example ASM code. I called sparkfun and they said the ASM code from the first module wont work on the second module because the pin outs are different but I couldnt find out any more. Im not sure if it will be easily enough to program the second one, or even if the ASM from the first product will work with this one with a very minor adjustment.

I appologise for all the info / questions, but this is starting to stress me out.

EDIT: I found this post which contains some PIC assembly code for the nRF24L01 - perhaps this will be a better route to go down?
http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=72375

 

[DirtyLude]

It sounds like you are really starting from level zero. Take the modules you bought and go through Nigel's tutorials.

 

[Spadez]

Afraid so. Is using these modules that I purchased actually going to cause me a lot of headaches though? The impression I got was that they are extremely unreliable.

 

[wannaBinventor]

The RFM12B modules are cheap -- but can be a little bit complicated with all the different configurations. At times the datasheets are somewhat confusing. I say "datasheets" because the RFM12B module uses a chip that is compatible with MichroChip's MRF49XA and Silicon Lab's Si4421.

If you look around you can still find them in stock at other places --- probably for less than $7 per transceiver. I have some that I got direct from Hope RF that I would perhaps part with -- pm me if interested. Understand that these may be a little over the beginners head. I know it took me A LOT of time reading datasheets and troubleshooting before I got a link running with my PIC ASM program.

An LM317 variable regulator and a PIC with "LF" in the part number will let you run it down to it's required voltage range.

How much ASM PIC programming experience do you have?

Why are you set on a two wire interface? Pins are cheap -- and a PIC with hardware SPI could probably make the process easier.

 

[DirtyLude]

Afraid so. Is using these modules that I purchased actually going to cause me a lot of headaches though? The impression I got was that they are extremely unreliable.

It would be easier for you to use the modules you bought, because it looks like learning to program is one of your requirements and Nigels tutorials step through the programming and setup.

There are really nice libraries and tutorials for setting up transmitter/receiver pairs with Arduino, but that doesn't sound like an option for you.

 

[Spadez]

Unfortunatly not. Ill give these a go, the trouble iseven the people at Sparkfun dont seem to like those modules much.

How about using this assembly code as a starting point:
View topic - nRF24L01 Assembly Code :: AVR Freaks

With this transceiver:
SparkFun Electronics - Transceiver nRF24L01+ Module with RP-SMA

This gives me a strong transceiver with a lump of assembly code to build upon, plus I get this in the UK.

 

[Spadez]

Sorry I just saw your reply wannaBinventor.

I have plenty of pins but I was told bit bashing was an easy method. Ive found some code that deals with SPI which helps a lot but im not sure which modules will work with that. My assembly is very basic, but id rather have something more complicated that I can build upon than nothing at all.