SWRU270
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procedure. To do this, you will first need to click the “Read / Write” tab in BTool. Select the option “Read
Using Characteristic UUID” under the “Sub-Procedure” option in the “Characteristic Read” section at the
top of the screen. Enter “F1:FF” (note that the LSB is entered first, and the MSB is entered last) in the
“Characteristic UUID” box, and click the “Read” button.
An attribute protocol Read by Type Request packet gets sent over the air from the dongle to the keyfob,
and an attribute protocol Read by Type Response packet gets sent back from the keyfob to the dongle. The
value “01” is displayed in the “Value” box, and “Success” is displayed in the “Status” box. In addition,
the message window will display information on the Read by Type Response packet that was received by
the dongle. The message includes not only the characteristic’s data value, but also the handle of the
characteristic value (0x0011 in this case).
Figure 21
4.3.2 Writing a Characteristic Value
In the previous section, the handle of the first characteristic in the SimpleGATTProfile was found to be
0x0011. Knowing this, and based on the fact that the characteristic has both read and write permissions,
it is possible for us to write a new value. Enter “0x0011” into the “Characteristic Value Handle” box in
the “Characteristic Write” section, and enter any 1-byte value in the “Value” section (the format can be
set to either “Decimal” or “Hex”). Click the “Write Value” button.
An attribute protocol Write Request packet gets sent over the air from the dongle to the keyfob, and an
attribute protocol Write Response packet gets sent back from the keyfob to the dongle. The status box will
display “Success”, indicating that the write was successful.
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