Computing stuff tied to the physical world

RFM12 vs RFM12B – revisited

In AVR, Hardware on May 6, 2009 at 00:01

Now that the RFM12 is working, here’s the list of differences between RFM12 and RFM12B I’ve come across:

  • The RFM12 works up to 5V, the RFM12B only up to 3.8V (but it won’t be damaged by 5V).
  • The RFM12 needs a pull-up resistor of 10..100 KΩ on the FSK/DATA/nFFS pin, the RFM12B doesn’t.
  • The RFM12 can only sync on the hex “2DD4” 2-byte pattern, the RFM12B can sync on any value for the second byte, not just D4.

More differences, found by Reinhard Max:

  • The B version can be set to a single sync byte.
  • The “PLL setting command” (CCxx), which only exists on the RFM12B.
  • Different values for RX sensitivity and TX output power.
  • A slightly different formula to calculate the time of the Wake-Up Timer.

Here is the back of the module, RFM12 on the left, RFM12B on the right:

RFM12 vs RFM12B

(these also happen to be for different frequency bands, as you can see)

And here is the front view, with RFM12 on the right and RFM12B on the left this time:

RFM12 vs RFM12B

The RFM12 unit on the right has a pull-up resistor added on top – note also the exposed pads at the top.

Note how the alignment of the solder pads on the JeeNode PCB is a bit off – these are v1 PCB’s, the v2 PCB’s have better alignment.