User Manual

MRF24J40MC
DS00000A-page 8 Preliminary © 2011 Microchip Technology Inc.
1.3.2 ENERGY DETECTION (ED)
Before performing an energy detection (see Section
3.6.1 “RSSI Firmware Request (RSSI Mode 1)” in the
“MRF24J40 Data Sheet” (DS39776)), perform the
following steps:
1. Configure the internal RF state machine to normal
operation (TESTMODE (0x22F<2:0>)
= 000).
2. Configure GPIO2 and GPIO1 direction for
output (TRISGP2 (0x34<2>) = 1 and TRISGP1
(0x34<1>) = 1).
3. Set GPIO2 (0x33<2>) = 1 and GPIO1
(0x32<1>) = 0. This enables the LNA and
disables the PA.
4. Perform the energy detection following the steps
in Section 3.6.1 “RSSI Firmware Request (RSSI
Mode 1)” in the “MRF24J40 Data Sheet”
(DS39776).
1.3.3 SLEEP
To get the lowest power consumption from the
MRF24J40MC module during Sleep, it is necessary to
disable the PA, PA voltage regulator and LNA. To do
this, perform the following steps:
1. Configure the internal RF state machine to normal
operation (TESTMODE (0x22F<2:0>) = 000).
2. Configure the GPIO3, GPIO2 and GPIO1
direction for output (TRISGP3 (0x34<3>) = 1,
TRISGP2 (0x34<2>) = 1 and TRISGP1
(0x34<1>) = 1).
3. Set GPIO2 (0x33<2>) = 0 and GPIO1 (0x32<1>)
= 0. This disables the LNA and the PA.
4. Set GPIO3 (0x33<3>) = 0. This shuts down the
voltage regulator U5 that supplies 2.2 volts to
the PA.
5. Put the MRF24J40 to Sleep following the steps
in the “MRF24J40 Data Sheet” (DS39776).
When waking the module, re-enable the PA/LNA mode.
Note: The LNA will amplify the received signal.
The RSSI value will include the receive
signal strength plus the LNA amplification.