The SCK is used in the SPI communications and is part of the SPI standard. The SCK is provided by the MCU, not the RFM12.

The on-board Crystal can provide a CLK output to drive a MCU or anything else that requires an oscillator and can be controlled up to 10MHZ. I use this to test my SPI communications between the MCU and the RFM12. i.e. I put a frequency counter or oscilloscope onto the CLK pin of the RFM12 and then send through a command to the to change the frequency.

Yes more than likely, that header file was written a few years a go and Hope have released some revisions to the original document I was then working from.

Stephen…

I was looking at the RFM12.H header file you have created and found a mysterious RFM12_PLL_LPX in the PLL setting command definitions. In the latest data sheet this location is a fixed 1. Is this a throwback to an old version of silicon?

Colin

I am sorry, I just couldn’t let go. Still working on RFM12B communication and I found out that in my case I get better results transmitting using a slightly different method then I have seen in Hope and other code. For writing the data I use:
void rf_write_data( BYTE data )
{
WORD status;

status = rf_write_cmd( 0x0000 );
if( (status&0x8000) == 0x8000 )
rf_write_cmd( 0xB800 + data );
}

This is, as you can see, very similar to the way I receive data:
BYTE rf_read_data( void )
{
WORD status;
WORD data;

return (data&0x00FF);
}


Willem

In the meantime, I did manage to get it working though. Both RFM01 and RFM02 and RFM12B. In 868 and 433 frequencies and mixing them as well. Once you get the hang of it they are great and seem to be pretty robust as well.

I received a lot of support from Hope (and some help). But using a logic analyzer is the thing that really helped me progress this.

Thanks and all the best for the new year!

I am trying to get the RFM12 to work with the PIC16F877A, but I am totally lost about how to get the rf module configured. I got my two pic devices working fine in SPI, wired up. But when I try to integrate the rf module, it doesn’t seem to work at all. I’ve got a couple of questions baffling me, hope you can answer them for me.
1. How should the rfm12 module be connected to the pic? according to the rf12 programming guide example 2, it used RB7 – 4, but the SPI interface uses RC5 – 3.
2. How are the rf module parameters configured? I understand the configuration commands are given in the programming guide, but I don’t know how they are sent to the rf module, but using the code in the programming guide?
3. If I get the rf module setup, how do I send data out, do I write to SSPBUF or do I have to use some other function?

Thanks in advance

you are correct the SCK is provided by the MCU, bu tyou don’t have to use the MCU SCK port, the SCK is used to clock in (and out) the bits that make up the command being sent to the RFMxx. you can bit bang the spi quite easily, I initially did this on the PICs as I couldn’t get the onboard SPI working, AVR the onboard SPI works a treat. below is what I did to bitbang the SPI
/*

CMD<<=1; // Shift left for next bit to send
RESULT<<=1; // Shift left for next bit to receive
if(SDI) // Check if we received a high on SDI
RESULT |= 0x0001; // RESULT LSB = 1
}
SCK=0; // SCK LOW
rfm12_cs = 1; // CS HIGH - Finished Sending Command
}


the bit banging is done in these


// Bitbang binary 1 via SPI
void Write1(void)
{
SDO=1;
SCK=0;
nop();
nop();
nop();
nop();
nop();
nop();
nop();
nop();
nop();
nop();
nop();
nop();
nop();
nop();
nop();
nop();

nop();
}


I´v read your blogs with interest. I too have been struggling with these. As a matter of fact with their little brother and sister: RFM01 and RTX02 I believe they are called. The chips are actually made (or sold) by Silicon Labs and they do have a lot of extra information on them. Including an application that lets you define all your parameters and it will then create a header file for you to use.
However, I am puzzled by a few things. They claim to have a proper SPI interface but I don’t think they do. For one their data send protocol doesn’t match which is something they even mention in their datasheets.
But what I do not understand is how the SCK pin works. As far as I can see they do need a clock from the master. If the master is your MCU then I don’t know how you could do that without actually using your MCU’s SCK port?! Well, you could actually generate the clock yourself by using a timer. However in all the sample code I have seen floating around including yours, the SCK is just an outport pin that is pulled low and released again. Am I wrong in this?

Thanks
Willem

P.S. Sorry for bumping this thread…