Routing RF core signals to physical pins

The various hardware units on the RF core provide 12 internal hardware signals that indicate various events. These signals are defined in Table 8.. Not all signals are documented, though.

Table 8. Internal signals of different functional units on the RF core.

Index	Signal identifier	Default mapping	Description
0	CPE_GPO0	RFC_GPO0	Controls an external LNA front-end. High when the LNA must be enabled, otherwise low.
1	CPE_GPO1	RFC_GPO1	Controls an external PA. High when the PA must be enabled and otherwise low.
2	CPE_GPO2	RFC_GPO2	Goes high when the synthesizer calibration starts and low when the calibration is done.
3	CPE_GPO3		n/a
4	MCE_GPO0		Binary data signal that goes to the modulator when sending.
5	MCE_GPO1		Binary data signal that comes from the demodulator when receiving.
6	MCE_GPO2		n/a
7	MCE_GPO3		n/a
8	RAT_GPO0	RFC_GPO3	Goes high when a transmission is initiated and low when the transmission is done. Can be used for accurate timing synchronization.
9	RAT_GPO1		Goes high when sync word is detected and low either when the packet has been received or reception has been aborted. Not available for IEEE 802.15.4 RX commands. Requires an additional override (uint32_t)0x008F88B3
10	RAT_GPO2		General purpose RAT output. Configurable via CMD_SET_RAT_OUTPUT.
11	RAT_GPO3		General purpose RAT output. Configurable via CMD_SET_RAT_OUTPUT.

Each of those 12 signals can be routed to any physical GPIO pin via the RF core doorbell register SYSGPOCTL. The doorbell register provides 4 outputs: RFC_GPO0 .. RFC_GPO3. This means that at most 4 output signals from Table 8. can be used at the same time. The signals RFC_GPO0 .. RFC_GPO3 have a default mapping on power up.

In addition, the RF core provides two input signals: RFC_GPI0 and RFC_GPI1. These are tied to the radio timer on the RF core and can be used, for instance, to trigger an RF operation command. For a usage example, please refer to External triggers TRIG_EXTERNAL.

Routing internal signals to the doorbell register

The default mapping from Table 8. can be changed by writing to the SYSGPOCTL register. For instance, to map RAT_GPO2 => RFC_GPO0 and MCE_GPO0 => RFC_GPO1, use the following code snippet:

#include <ti/devices/${DEVICE_FAMILY}/inc/hw_rfc_dbell.h>

// Map RAT_GPO2 to RFC_GPO0
// Map MCE_GPO0 to RFC_GPO1
HWREG(RFC_DBELL_BASE + RFC_DBELL_O_SYSGPOCTL) =
        RFC_DBELL_SYSGPOCTL_GPOCTL0_RATGPO2 | RFC_DBELL_SYSGPOCTL_GPOCTL1_MCEGPO0;

Please note that this can only be done when the RF core is powered up. The signal mapping on the RF core is reset on each power-up cycle. In order to apply a custom mapping automatically during power-up, apply the register change via an override instead:

#include <ti/devices/${DEVICE_FAMILY]/inc/hw_rfc_dbell.h>

// Overrides for CMD_PROP_RADIO_DIV_SETUP
static uint32_t pOverrides[] =
{
    // Set the SYSGPOCTL register
    HW_REG_OVERRIDE(0x1110, RFC_DBELL_SYSGPOCTL_GPOCTL0_RATGPO2 | RFC_DBELL_SYSGPOCTL_GPOCTL1_MCEGPO0),
    // ...
}

Routing doorbell signals to GPIO pins

After the signal mapping has been established on the RF core, the doorbell GPIO signal can be routed to a physical pin or vice versa by the help of the PIN driver:

#include <ti/drivers/pin/PINCC26XX.h>

// Map RFC_GPO0 to IO 23
PINCC26XX_setMux(pinHandle, IOID_23, PINCC26XX_MUX_RFC_GPO0);
// Map IO 26 to RFC_GPI1
PINCC26XX_setMux(pinHandle, IOID_26, PINCC26XX_MUX_RFC_GPI1);

This mapping is permanent as long as the GPIO driver is initialized correctly.