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Advanced application features
Note
By default, all Digital I/O lines have internal pull-up resistors enabled with the PR command.
This causes inputs to float high. You can use the PD command to change the direction of the internal
pull-up/down resistors. The XBee SX 868 RF Module uses an internal reference voltage of 2.5 V for ADC
lines, but you can use the AV command to set it to 1.25 VDC.
General Purpose Flash Memory
XBee SX 868 RF Modules provides 61 2048-byte blocks of flash memory that an application can read
and write to. This memory provides a non-volatile data storage area that an application uses for many
purposes. Some common uses of this data storage include:
Storing logged sensor data
n
Buffering firmware update data for a host microcontroller
n
Storing and retrieving data tables needed for calculations performed by a host microcontroller
n
The General Purpose Memory (GPM) is also used to store a firmware update file for over-the-air
firmware updates of the device itself.
Access General Purpose Flash Memory
To access the GPM of a target node locally or over-the-air, send commands to the MEMORY_ACCESS
cluster ID (0x23) on the DIGI_DEVICE endpoint (0xE6) of the target node using explicit API frames. For a
description of Explicit API frames, see
To issue a GPM command, format the payload of an explicit API frame as follows:
Byte offset
in payload
0
1
2
4
6
8
* Specify multi-byte parameters with big-endian byte ordering.
When a device sends a GPM command to another device via a unicast, the receiving device sends a
unicast response back to the requesting device's source endpoint specified in the request packet. It
does not send a response for broadcast requests. If the source endpoint is set to the DIGI_DEVICE
endpoint (0xE6) or Explicit API mode is enabled on the requesting device, then the requesting node
outputs a GPM response as an explicit API RX indicator frame (assuming it has API mode enabled).
XBee® SX 868 RF Module User Guide
Operate in API
Number of
bytes
Field name
1
GPM_CMD_ID
1
GPM_OPTIONS
2*
GPM_BLOCK_NUM
2*
GPM_START_INDEX
2*
GPM_NUM_BYTES
varies
GPM_DATA
General Purpose Flash Memory
mode.
General field description
Specific GPM commands are
described in detail in the topics that
follow.
Command-specific options.
The block number addressed in the
GPM.
The byte index within the addressed
GPM block.
The number of bytes in the GPM_
DATA field, or in the case of a READ,
the number of bytes requested.
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