RFM42B Datasheet, PDF (26/51 Pages) List of Unclassifed Manufacturers – ISM TRANSMITTER

RFM42B/43B
4.2.2.3. Direct Mode using SPI or nIRQ Pins
In certain applications it may be desirable to minimize the connections to the microcontroller or to preserve the
GPIOs for other uses. For these cases it is possible to use the SPI pins and nIRQ as the modulation clock and
data. The SDO pin can be configured to be the data clock by programming trclk = 10. If the nSEL pin is LOW then
the function of the pin will be SPI data output. If the pin is high and trclk[1:0] is 10 then during TX mode the data
clock will be available on the SDO pin. If trclk[1:0] is set to 11 and no interrupts are enabled in registers 05 or 06h,
then the nIRQ pin can also be used as the TX data clock.
The SDI pin can be configured to be the data source in TX mode if dtmod[1:0] = 01. In a similar fashion, if nSEL is
LOW the pin will function as SPI data-in. If nSEL is HIGH then in TX mode it will be the data to be modulated and
transmitted. Figure 9 demonstrates using SDI and SDO as the TX data and clock:
TX on
command
TX mode
TX off
command
TX on
command
TX mode
TX off
command
nSEL
SDI
SPI input
don’t care
SPI input
MOD input
SPI input don’t care SPI input
MOD output
SPI input
SDO
SPI output
don’t care
SPI output
Data CLK
Output
SPI output don’t care SPI output
Data CLK
Output
SPI output
Figure 9. Microcontroller Connections
If the SDO pin is not used for data clock then it may be programmed to be the interrupt function (nIRQ) by
programming Reg 0Eh bit 3.
4.2.3. PN9 Mode
In this mode the TX Data is generated internally using a pseudorandom (PN9 sequence) bit generator. The primary
purpose of this mode is for use as a test mode to observe the modulated spectrum without having to provide data.
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