My sample order of the RFM22 were waiting for me when I arrived home late last night.
Here is a picture of the RFM22 (Left) next to the RFM12B (Right). Pretty much the same physical size, but more pins, and a lot of very small discrete components.
So What’s New?
These new transceiver modules from HopeRF appear to be based on Silicon Labs Si4431 and Si4432 RF Chips. Silicon Labs purchased Integration, from where the RFM12B were based on their EzRadio Series of transceiver chips.
It looks like there are a heap of new feature available, (too many to list here), including some onboard lower MAC smarts called EzyMac, while not as nice as the 802.15.4 MAC layer it looks like it can simplify things such as:
- Automatically adding pre-amble and sync bytes.
- Automatic packet size – you just push bytes into the Tx FIFO and it will create the packets of a fixed size and send for you.
- Built in basic frequency hopping.
- Built in Data Whitening, Manchester Encoding, and CRC
Some more niceties:
- 64Byte FIFO.
- Onboard A/D, allows access to read such things as an onboard Temperature Sensors, Voltage buses.
- x2 configurable GPIO ports.
- More Rx Sensitivity than the RFM12B.
- More Tx power than the RFM12B
- Lower Operating voltage.
- 8bit RSSI value.
- Three different modulation schemes to select from.
Some not so niceties:
- More current draw on Rx than the RFM12B.
- More current draw on Tx than the RFM12B (understandable seeing it also has a higher Tx Power).
- Costs about twice as much as the RFM12B ~ $USD6.00 in sample quantities direct from HopeRf vs ~$USD3.00 for the RFM12B.
- Heaps more commands/Registers to learn.
- No onboard encryption.
|Max Data Rate||115.2kbps||1-128Kbps||1-128Kbps|
|Max Power Output (Tx)||5dBm@433MHz
|Max Supply current (Tx)||22mA@433MHz
|Max Supply Current (Rx)||11mA@433MHz
|Low Battery Detect||Yes||Yes||Yes|
|Frequency Hopping Capable||Yes||Yes||Yes|
|Wideband or Narrow Band Design||Wideband||Wideband or Narrowband||Wideband or Narrowband|