RFM22
8.8. GPIO Configuration
Three general purpose IOs (GPIOs) are available. Numerous functions such as specific interrupts, TRSW control,
Microcontroller Output, etc. can be routed to the GPIO pins as shown in the tables below. When in Shutdown mode
all the GPIO pads are pulled low.
Note: The ADC should not be selected as an input to the GPIO in Standby or Sleep Modes and will cause excess current
consumption.
POR
Def.
Function/D
escription
GPIO0
D7
D6
D5
D4
D3
D2
D1
D0
Add R/W
gpio0
gpio0dr
v[0]
R/W
pup0
Pup1
Pup2
gpio0[4] gpio0[3] gpio0[2] gpio0[1] gpio0[0]
gpio1[4] gpio1[3] gpio1[2] gpio1[1] gpio1[0]
gpio2[4] gpio2[3] gpio2[2] gpio2[1] gpio2[0]
00h
00h
00h
00h
0B
Configuration drv[1]
GPIO1 Gpio1
Configuration drv[1]
GPIO2 Gpio2
gpio1dr
v[0]
R/W
0C
gpio2dr
v[0]
R/W
0D
Configuration drv[1]
I/O Port
extitst[
1]
R/W
extitst[2]
extitst[0]
itsdo
dio2
dio1
dio0
0E
Configuration
The GPIO settings for GPIO1 and GPIO2 are the same as for GPIO0 with the exception of the 00000 default
setting. The default settings for each GPIO are listed below:
GPIO
00000—Default Setting
POR
GPIO0
GPIO1
GPIO2
POR Inverted
Microcontroller Clock
The diagrams in Figure 30 show two different configurations/usage of the GPIO. In Configuration A an external
sensor is used and the GPIO is configured as an input with the 00101 External Interrupt, Rising Edge setting.
When the sensor is triggered the nIRQ pin will go high and the microcontroller will be able to read the interrupt
register and know that an event occurred on the sensor. The advantage of this configuration is that it saves a
microcontroller pin. This application utilizes the high output power so a TRSW is required.
In Configuration B, the module is configured to provide the System Clock output to the microcontroller so that only
one crystal is needed in the system, therefore reducing the BOM cost. For the TX Data Source, Direct Mode is used
because long packets are desired with a unique packet handling format already implemented in the microcontroller.
In this configuration the TX Data Clock is configured onto GPIO0, the TX Data is configured onto GPIO1, and the
Microcontroller System Clock output is configured onto GPIO2. In this application only the lowest output power
setting is required so no TRSW is needed.
For a complete list of the available GPIO's see ―Register 0Ch. GPIO Configuration 1,‖ ,―Register 0Dh.
GPIO Configuration 2,‖, and ―Register 0Eh. I/O Port Configuration,‖.
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