LCD Extension Board
This board turns MyNOR into a "real" computer. It adds a display, keyboard,
sound, real-time clock and a temperature sensor to the MyNOR base board. With this board
you do no longer need the serial terminal to communicate with MyNOR. This board allows you
to use MyNOR alone, e.g. for simple games like Tic Tac Toe, Minesweeper or a
car driving game. MyNOR automatically detects the presence of the board
and displays a menu that allows you to load one of eight programs from the EEPROM.
The keypad is read out in a multiplexed manner to reduce the number of required I/O pins.
The LCD is controlled in 8-bit mode to increase the transfer speed. The real-time clock chip
and the temperature sensor are connected via I2C. The sound output is as simple as possible:
A D/A-converter (connected via SPI) controls a VCO chip that generates frequencies in the range
from 262 Hz to 2093 Hz (= three octaves).
As you can see, a small 32 Ohm speaker is mounted on the board. There is also an additional
IC (74HCT00) that is used as speaker driver and for muting. The right-angled header on the left
exposes the I2C and SPI bus, and enables the connection of other peripheral devices to the board.
The RTC (real-time clock) has three functions: First, it is a clock. Second, it is used to
generate a 1 Hz signal as time base for the MyNOR computer (MyNOR can use it to "simulate"
2 timer interrupts per second with it), and third, the clock chip is used to calibrate the
sound output because it can be configured as an event counter that is used by the calibration
software for frequency measurement.
Schematics and BOM
Click on the schematics to see it in full resolution (PDF).
You can get the design files in the download section.
All components can be sourced from
A great PCB manufacturer is JLCPCB (China).
All you have to do is upload the zip-file that contains the Gerber data to JLCPCB.
|BAT1||battery holder for CR2032|
|C1 C2 C4 C5||100nF|
|C3||optional, for RTC tuning|
|C6||10nF / 5%|
|C7 C8||10µF / 16V|
|C9||1µF / 16V|
|D1 D2 D3 D4 D5 D6 D7 D8||BAT41|
|J1 J2||Header 2x10 pin, 2.54mm|
|J3||Header 1x8 pin, 2.54mm, right angle|
|J4||USB type B mini connector|
|R2 R3||22 kOhm|
|SP1||Speaker 32 Ohm|
|SW1 - SW15 (15 pcs)||push button 6x4.3mm|
|TR1||250 Ohm, Piher PT6S|
|TR2 TR3||10 kOhm, multi-turn trimmer|
|TR4||10 kOhm, Piher PT6S|
|U3||TMP75AIDR (or LM75)|
|Y1||Crystal 32.768 kHz|