Schematics

Here you can download the schematics for the mainboard. Because the 80c552-board has to be mounted on the mainboard, the connectors are of course the same, here K1 and K2.

Display

On K3 you can connect a graphical display. In this case it is a display with 128x64 pixel and can be ordered from Conrad using the ordering number 187429. This is the display NLC-128x064 of the NanYa corporation, which is controlled by two KS0108 controllers.

All control- and datalines of the display are connected to I/O-ports of the microcontroller. P4 is used for the data transfer from and to the display. For the controllines I used so portpins, which were still unused by the controller board. The backlight can be switched on by a MOSFET, which is controlled by bit 6 on RAM-address 0x0000 (memory-mapped IO)

RS232-interface

Because the conversion to RS232 voltage levels is already done on the controller board, here only a 9-pin sub-D-connector is needed. The handshakelines are connected through.

EEPROM

To save configuration data there is a 1 kB EEPROM (IC3) on the mainboard. The EEPROM is controlled by I²C. It is possible to use other serial memory device instead of the 24C04.

Realtime Clock

The PCF8583 (IC6) is a RTC, which is also controlled by über I²C. Inaccuracy of the crystal can be adjusted by C8.

RC5 IR remote receiver

Around IC1 a receiver for an IR remote control, which supports the RC5-protocoll is drawn.

Keyboard input

Up to 6 keys can be connected to K6. Furthermore a LED can be connected, which can be switched by a portpin and which also serves as a status LED for the IR-receiver.

Opto-decoupled outputs

IC7 with the following part are used in my preamplifier to select the analog inputs. Because those have a symetrical power supply, the voltage levels have to be converted. To do this, two optocouplers (IC4/IC8) and a schmidt-trigger (IC9) are used. Aditionally a BCD-to-decimal-converter is needed.

Power supply

T4 and T5 switch the external power output and the analog power supply on the power module. Both transistors can be used for other purposed though.