Alpha modules from RF Solutions

[gbbickerton]

Hi has anyone had any success with the alpha modules? I am using bit bang SPI on an plain 18 but so far I have not been able to change anything on the transmitter module. I have checked and double checked that the right signals are going to the right pins with an oscilloscope but the alpha module never shows any change (I have tried to change the clock output frequency so that I can monitor if it changes).

Barry

 

[hippy]

Not used them, but presume these are the modules ...

http://www.rfsolutions.co.uk/acatalog/Alpha_TX_RX_Modules.html

The best approach for getting SPI comms to work I find is to read something known and get that right but it can be a haul when you need to have everything right or nothing happens.

Perhaps post your circuit and program so people can check if it matches their interpretation of the datasheets. A Google search can also turn up example code and other peoples' experience which can help point to what's not quite right.

 

[srnet]

Yep, post a circuit diagram.

I can think of a couple of things that stop SPI working on a PICAXE .......

 

[gbbickerton]

They are the ones

They are manufactured by Hope, type RFM02 for the transmitter, I have data sheets from RF solutions from hope and from silicon labs who make the chips in the module while they are good in the detail none of them give much idea how the fetures interact or how to use them for a simple fsk link.

Also if anyone has had trouble with the quasar quasi am/fm modules I have found that anything under 50M is to close together without coiling up the antenna to reduce sensitivity.

Of interest to others, may be the way most modules dynamically set the level to differentiate a high from a low (bit slicing), and this has a short time constant so sending raw serial data results in the level moving up and down with data containing many '0's or '1's which ends up as corrupt data, so manchester encoding which contains equal numbers of 1's and 0's solves this, I am using the encoders and decoders from rev ed with good success.

 

[manuka]

There are numerous 433 MHz modules that are far easier to use than these (ALPHA) HopeRF RFM02 offerings. Do NOT be deceived by their lean looks & cheapness-previous Forum postings indicate that they're quite a handful!

What exactly are you wishing to achieve? Range needs? Interference likely? Budget? Data rates?

 

[hippy]

These modules do seem more complicated to setup and use but it should be within a PICAXE's capability. The concerns for me would be what configuration to use ( some RF experience there and with the devices themselves would be handy though POR values may be good enough ), and whether a PICAXE can pull data from the receiver quickly enough before FIFO overflow.

 

[gbbickerton]

Problem solved

I have found an error in the 'shiftout MSB first' routine which is in the basic command help file and the shiftin_out.bas example file the 'low sdata' and 'high sdata' are the wrong way around and invert the data, the alpha modules modules work fine now that I have corrected that. The modules do require a bit of setting up and require a dedicated picaxe to set them up every time they are switched on but once the code is set up it is easy to change the parameters sent to the modules, I havn't got them talking to each other yet but I have fsk data coming out of the transmitter on the right frequency, so its time to get the reciever going tomorrow.

 

[gbbickerton]

The power on values are with the modules in sleep mode for low power consumption so they will not work off the shelf, also i am not planning to use the fifo buffer for now, I thought I would try to get FSK working to keep things simple. I bought them just to see if I could make them work and maybe provide a solution to other picaxe users If I am sucessful I will post the code here, so far the programming code only uses about 75 bytes so there is plenty of room left for a program

 

[manuka]

I've NOT personally used these modules, so thanks for posting this discovery! In spite of my general enthusiasm for HopeRF's products,their "Chinglish" manuals are indeed confusing.

 

[hippy]

I have found an error in the 'shiftout MSB first' routine which is in the basic command help file and the shiftin_out.bas example file the 'low sdata' and 'high sdata' are the wrong way around and invert the data

It appears you are correct and please accept our apologies for that. I've made a note of the error.

 

[gbbickerton]

I have had these working sending text to a terminal program on my PC but after soldering another wire onto the rx it looks like i fried it (maybe i had the programming lead plugged in and got an earth loop or something)
I have found that the frequency read out on my frequency counter does not match the programmed frequency when the carrier is unmodulated, so do not do as i did and tweak the settings to get the carrier on the right frequency or they will not work

 

[manuka]

Such freq. "deviation" is yet another reason why a UHF scanner (or even a simple 433 MHz receiver) is handy.