PIC microcontroller. USB Control module.
They are two optional control modules available: USB and I2C Bus
The tiny SCR Preselector USB is located in a separate module board to avoid introducing
noise generated by the microprocessor itself and the noisy USB bus.
A 18F2455 PIC microcontroller is used. It incorporates a full speed (v2.0) USB port periph-
eral to communicate with the PC.
A four MHz quartz crystal is connected to the oscillator pins generating via internal PLL
circuitry, the 48MHz clock for the microcontroller core and the 96 MHz clock to the USB
peripheral.
In circuit serial programming (ICSP) connector is provided to let programming the microcon-
troller firmware without remove it from the PCB.
Two power drivers ULN 2803 ICs interface the PIC microcontroller output ports with the
relays on the Band Pass Filter module.
Connection to the Multi-band pass filter module is done with 16 ways ribbon cable and IDC connectors on both sides, carrying control
signals and power supply.
To suppress ESD and other transient over voltage events on the USB signals lines, an array of Avalanche Diode Array are connected to
them.
A carefully PCB design and strong decoupling avoid introduce noise on the filters board.
Standard 2.5mm diameter power jack and type B USB connector are used.
Power supply: 12V DC/250mA max.
I2C Bus control module
The tiny SCR Preselector I2C Bus control module, located in a separate module board, lets to handle
easily the Band pass Filter board from an existing control system on your radio project due the simple
implementation of the I2C protocol on any microcontroller.
It is based on the well know PCF8575 remote 16-bit I/O expander for I2C Bus. Two power drivers ULN
2803A interface the PCF8575 output ports with the relays. I2C addresses are configured through J4, J5
and J6 pin headers and J2 and J3 headers connect pull-up resistors to the I2C line if is needed.
Three auxiliary ports are provided for optional controls and/or signalling. J7 are Input/Output ports, 5volts
level and J8 are buffered ports at 12volts level.
J11 provides an open-drain interrupt output which can be connected to the interrupt logic of the microcon-
troller.
Connection to the Multi-band pass filter module is done with 16 ways ribbon cable and IDC connectors
on both sides, carrying control signals and power supply.
A carefully PCB design and strong decoupling avoid introduce noise on the filters board.
Features of the module are:
- 16 bits standard I2C serial bus interface.
- 100Kbits/s and 400kbits/s FAST I2C Bus.
- Three auxiliary Input/Output ports for optional controls and/or signalling.
- Open-drain interrupt output.
- Sixteen latched outputs with high current drive capability.
- Programmable address by 3 hardware address pins.
- Optional I2C Bus lines pull-up resistors.
- Up to eight modules can share the same I2C Bus.
- Compatible with most microcontrollers.
- Power Supply: 12V DC/250mA max.
- Dimensions: 62x47mm. (2.44x1.85 inch)
Manual
tiny SCR PRESELECTOR
PIC 18F2455
Control module diagram
Full speed USB v2
Plug and Play
Windows2K, XP, Vista, 7 OS
Control from PC
ICSP Service Coonnector
Six ports future features
expansion connector
Power Drivers
+12V DC/400mA max
© Heros Technology Ltd 2006. All rights reserved
