I/O line passing

You can configure XBee/XBee-PRO SX RF Modules to perform analog and digital line passing. When a device receives an RF I/O sample data packet, you can set up the receiving device to update any enabled outputs (PWM and DIO) based on the data it receives.

Digital I/O lines are mapped in pairs; pins configured as digital input on the transmitting device affect the corresponding digital output pin on the receiving device. For example: DI5 (pin 25) can only update DO5 (pin 25).

For Analog Line Passing, the XBee/XBee-PRO SX RF Module has two PWM output pins that simulate the voltage measured by the ADC lines AD0 and AD1. For example, when configured as an ADC, AD0 (pin 33) updates PWM0 (pin 7); AD1 (pin 32) updates PWM1 (pin 8).

The default setup is for outputs to not be updated. Instead, a device sends I/O sample data out the serial interface if the device is configured for API mode (AP = 1 or 2). You can use the IU command to disable sample data output.

To enable updating the outputs, set the IA (I/O Input Address) parameter with the address of the device that has the appropriate inputs enabled. This effectively binds the outputs to a particular device’s input. This does not affect the ability of the device to receive I/O line data from other devices - only its ability to update enabled outputs. Set the IA parameter to 0xFFFF (broadcast address) to set up the device to accept I/O data for output changes from any device on the network.

For line passing to function, the device configured with inputs must generate sample data. Refer to Pin configurations for information on how to configure digital and analog sampling.

When outputs are changed from their non-active state, the device can be setup to return the output level to its non-active state. The timers are set using the Tn (Dn Output Timer) and PT (PWM Output Timeout) commands. The timers are reset every time the device receives a valid I/O sample packet with a matching IA address. You can adjust the IC (Change Detect) and IR (Sample Rate) parameters on the transmitting device to keep the outputs set to their active output if the system needs more time than the timers can handle.