NXP Semiconductors
UM11038
OM27642 Smart Lock KIT
UM11038
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User manual
COMPANY PUBLIC
Rev. 1.1 — 11 October 2018
407611
16 of 38
9. Communication protocol between QN and PN
Communication between QN and PN is done using two GPIO lines and UART
communication (115200 bps and data format 8N1).
The GPIO lines are used to power the PN (in case a Bluetooth Low Energy client
connects) or to wake-up QN (in case a card or phone is presented to the PN via NFC).
The UART is used to transfer data for
•
Handshake
•
Data exchange
Data is transferred using a single character command, a 2-byte length indicator and the
data bytes. All data is sent using little endian format.
Only during the handshake phase the PN sends repeatedly a single character ‘P’ without
any additional bytes until QN responds.
Fig 15. Communication interface between QN and PN