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4.11 Dual SCI communication ports
The SCI0 is used by D-Bug12 or serial monitor for developing and debugging user programs.
The SCI1 can be used by user’s application programs. The receiver of the SCI1 can receive
signals from many different devices, but only from one device at a time, or it will cause a signal
collision. The main header J51 and auxiliary header J23 are used to select which device the
SCI1 will receive. The J51 selects a source from J23, VGA camera module and XBee module.
The J23 selects a source from USB interface via P1 (USB jack), Async serial communication in
TTL logic level via J43, RS232 via P2 (DB9 connector) and RS485 via T2 (2-postion terminal
block).
1. When a jumper is installed vertically on the two leftmost pins of the J51, the SCI1 will
receive signal from one of four sources decided by the jumper on the J23.
2. When a jumper is installed vertically on the two middle pins of the J51, the SCI1 will receive
signal from VGA camera module and the jumper on the J23 has no effect.
3. When a jumper is installed vertically on the two rightmost pins of the J51, the SCI1 will
receive signal from XBee module and the jumper on the J23 has no effect.
4.12 RS485 communication port
U5, SN75176, converts the TTL signal from SCI1 to RS485 differential signals and vice versa.
PJ0 (pin 22) of the MC9S12DG256 is used to control the direction of RS485 communication. If
PJ0=0, the RS485 port, U5 DS75176, is set as a receiver port. If PJ0=1, the RS485 port, U5
DS75176, is set as a transmitter port.
4.13 External SPI interface
SPI port (J10) pinouts are as follows:
SPI port (J10) pinouts are as follows:
Pin 1
Pin 3
Pin 5
MISO (PS4)
SPSLK (PS6)
/SS (PS7)
Pin 2
Pin 4
Pin 6
VCC (5V)
MOSI (PS5)
VSS (GND)
Pin 2
Pin 4
/IRQ
PJ6 (SDA )
4.14 External I2C interface
I2C port (J2) pinouts are as follows:
Pin 1
Pin 3
Pin 5
VCC (5V)
PJ7 (SCL)
VSS (GND)