IA4420 Datasheet, PDF (26/29 Pages) List of Unclassifed Manufacturers – Universal ISM Band FSK Transceiver

IA4420
RX-TX ALIGNMENT PROCEDURES
RX-TX frequency offset can be caused only by the differences in the actual reference frequency. To minimize these errors it is suggested to use
the same crystal type and the same PCB layout for the crystal placement on the RX and TX PCBs.
To verify the possible RX-TX offset it is suggested to measure the CLK output of both chips with a high level of accuracy. Do not measure the
output at the XTL pin since the measurement process itself will change the reference frequency. Since the carrier frequencies are derived from
the reference frequency, having identical reference frequencies and nominal frequency settings at the TX and RX side there should be no
offset if the CLK signals have identical frequencies.
It is possible to monitor the actual RX-TX offset using the AFC status report included in the status byte of the receiver. By reading out the status
byte from the receiver the actual measured offset frequency will be reported. In order to get accurate values the AFC has to be disabled during
the read by clearing the "en" bit in the AFC Control Command (bit 0).
TYPICAL APPLICATIONS
REPEATER DEMO (915 MHZ)
Schematics
GND
SEL
CLK
IRQ
SCK
MISO
MOSI
FFS
FFE
INT/VDI
ARSSI
IC1
SJ1
2
1
P0.0
P0.1
1
2 28 _P0.2
27
TX 26
P0.3
P0.4
RX 25 _P0.5
24
23
P0.6
P0.7
P2.0
P2.1
P2.2
P2.3
P2.4
P2.5
P2.6
P2.7
14
13
12
11
10
9
8
7
22
21
20
19
P1.0
P1.1
P1.2
P1.3
P3.0/C2D
/RST/C2CK
6
5
18 _P1.4
17
16
15
P1.5
P1.6
P1.7
VDD ⁴
GND ³
C8051F311
1 SW1
4
5
3
6
R3 ^GND
820 R4
R5 820
820 R6
820 R7
VCC
1k
C1
100nF
GND
GND
3 TX
2 RX
1
J1
GND
3
2
1
DEBUG
GND
BATTERY
1
6V
2
C3
2,2uF
GND
IC3
1 _{IN OUT} 5
2 _GND
3 _{ON POK} 4
IA2112-3.3V
3,3V
C4
2,2uF
C5
C6
C7
1uF 100pF 10pF
GND
MOSI
SCK
SEL
MISO
IRQ
FFS
FFE
CLK
IC2
1 _SDI
NINT/VDI ^{16 INT/VDI}
2 _SCK
ARSSI ¹⁵
ARSSI
3 _NSEL
VDD ¹⁴
VCC
4 _SDO
RF1 ¹³
5 _NIRQ
RF2 ¹²
6 _{FSK/DATA/NFFS VSS} 11
7 _DCLK/CFIL
NRES ¹⁰
8 _CLK
XTL/REF ⁹
C2
IA4420-REVC
4,7nF
Q1
10MHz
GND
GND
X1
GND
26