User's Manual

10
6.7 RF Analog Multiplexor
The reader board switches the main RF channel to any one of the 12 available RF ports using Peregrine 4 SP4T PE42440 RF switches.
This part feature ESD protection as well low series resistance and insertion loss at the 13.56MHz carrier frequency. The RF switches
are the reflective type as absorptive are not required for this application.
The active channel is selected by the microcontroller per the following table:
Zone
Conn
MUX_SEL0
MUX_SEL1
MUX_SEL2
MUX_SEL3
1
J3
1
0
1
0
2
J9
1
1
1
0
3
J10
0
1
1
0
4
J4
0
0
1
0
5
J5
1
0
0
1
6
J11
1
1
0
1
7
J12
0
1
0
1
8
J6
0
0
0
1
9
J1
1
0
0
0
10
J7
1
1
0
0
11
J8
0
1
0
0
12
J2
0
0
0
0
6.8 Inductive Antenna Tuner
Each zone provides footprints to allow tuning for a wide range of custom antennas at each RF port. The technique of tuning a particular
antenna goes beyond this specification; however the goal of the tuning circuit is to convert the inherent impedance of the antenna
loop (@13.56MHz) to match the 50 Ohm impedance of the RFID transceiver circuit.
For example the VHC (Visual Holding Cabinet) RFID antenna measures 1.5uH@13.56MHz using a network analyzer. To convert the
impedance to 50Ohm, a 68pF series capacitor along with a 12pF parallel capacitor was used to allow the antenna to resonate at
13.56MHz. This results in a matched antenna with a read range of ~5 inches in air (no conductive metal near).
7. Software Description
7.1 Bootloader Support
The bootloader program is programmed in the auxiliary program flash memory and the microcontroller is configured to reset to
auxiliary flash reset location. The application is programmed to user program flash memory and the bootloader is used to write
application updates to user program flash memory in the field without using MCU programmer devices.
The bootloader is using the peripheral bus (P-BUS) to receive firmware update packets.
On power-up the bootloader checks if the user program memory has a valid application by calculating and comparing the application
CRC16 value. If a valid application is detected then the bootloader will jump to user program memory and start the main application.
If the user program memory application is not valid then the bootloader will not start the main application and wait for receiving
firmware update packets from the master device.