User Manual

Operation I/O support

XBee/XBee-PRO S2C 802.15.4 RF Module User Guide

neither based on the settings of the IA (I/O Input Address) and IU (I/O Output Enable) parameters.

For more information, see SO (Sleep Options) on page 77, IA (I/O Input Address) on page 91, and IU

(I/O Output Enable) on page 89.

Sample rate (interval)

The Sample Rate (Interval) feature allows enabled ADC and DIO pins to be read periodically on devices

that are not configured to operate in Sleep Mode. When one of the Sleep Modes is enabled and the IR

(Sample Rate) parameter is set, the device stays awake until IT (Samples before TX) samples have

been collected.

Once a particular pin is enabled, the appropriate sample rate must be chosen. The maximum sample

rate that can be achieved while using one A/D line is 1 sample/ms or 1 kHz. The device cannot keep up

with transmission when IR and IT are equal to 1 and we do not recommend configuring the device to

sample at rates greater than once every 20 ms.

I/O line passing

You can configure XBee/XBee-PRO S2C 802.15.4 RF Modules to perform analog and digital line

passing. When a device receives an RF I/O sample data packet, you can setup 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).

No I/O line passing occurs if the receiving device does not have the corresponding pins set for output.

For Analog Line Passing, the XBee/XBee-PRO S2C 802.15.4 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 in API mode, even if the destination node is not configured for API mode. 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

setup 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.

When outputs are changed from their configured state, the device can be setup to return the output

level to its configured state after a timer expires. 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 IT (Samples before TX) 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. Alternatively, the timers can be set to 0xFF,

which prevents them from expiring (in other words, the outputs remain in the state specified by the

input device indefinitely).

I/O line passing details

The same message is received for both I/O sampling and for I/O line passing. But I/O line passing only

occurs if IA matches the short or long address of the sending node or if IA is 0xFFFF to match a

sample from any node. The default value of IA is 0xFFFFFFFF, which prevents I/O line passing from

occurring on the node because no node has that address. Additionally, the receiving device must have