Legacy support
By default, the XBee 3 802.15.4 RF Module is configured to operate in a legacy configuration. This provides network and application compatibility with XBee S1 802.15.4 and XBee S2C 802.15.4 devices. AO (API Output Options) is used to determine:
- Which Digital I/O lines are sampled
- What sample frame type is used for outgoing transmissions
AO has no affect on received I/O sample data, but will determine the frame type emitted for received serial data.
Previous 802.15.4 firmwares on the XBee S1 and XBee S2C hardware had a limited set of I/O lines available. Valid DIO lines on these devices are from D0 through D8; I/O samples are transmitted over the air using a standard I/O sample packet using a Legacy data format. These platforms do not have an AO command and always output sample data in a legacy format if possible.
For the XBee 3 platform, digital I/O has been enhanced to be in parity with DigiMesh and Zigbee. You can now enable up to fourteen digital inputs for sampling: D0 through P4 as long as AO is not set to 2. In order to support these additional I/O lines, an enhanced I/O sample packet is sent over the air, which is not compatible with the S1 or S2C.
By default, the XBee 3 802.15.4 RF Module is configured to operate in a legacy configuration with AO set to 2. This allows you to sample D0 through D8. If you configure D9 through P4 as digital I/O, they are not sampled unless you set AO to 0 or 1.
For new designs, we recommend setting AO to 0 or 1 (Operate in API mode), which allows you to use additional I/O lines for sampling and easily allows you to switch to Zigbee or DigiMesh, as the API and I/O functionality are identical.
This table illustrates the various configuration combinations that are possible and the expected output:
|
Source |
Source AO value |
Destination |
Destination AO value |
Data format |
API frame on receiver |
|---|---|---|---|---|---|
|
XBee 3 |
0 or 1 |
XBee 3 |
0 or 1 |
Enhanced |
|
|
XBee 3 |
0 or 1 |
XBee 3 |
2 |
Enhanced |
|
|
XBee 3 |
0 or 1 |
S1 or S2C |
N/A |
N/A |
Legacy devices are unable to interpret the additional sample data and will discard the received packet. |
|
XBee 3 |
2 |
XBee 3 |
0 or 1 |
Legacy |
64-bit I/O Sample Indicator - 0x82 / 16-bit I/O Sample Indicator - 0x83 |
|
XBee 3 |
2 |
S1 or S2C |
N/A |
Legacy |
64-bit I/O Sample Indicator - 0x82 / 16-bit I/O Sample Indicator - 0x83 |
|
S1 or S2C |
N/A |
XBee 3 |
0 or 1 |
Legacy |
64-bit I/O Sample Indicator - 0x82 / 16-bit I/O Sample Indicator - 0x83 |
|
S1 or S2C |
N/A |
XBee 3 |
2 |
Legacy |
64-bit I/O Sample Indicator - 0x82 / 16-bit I/O Sample Indicator - 0x83 |
Refer to I/O sample data format for more information on the format of the incoming I/O sample data.
PDF
