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CYBOT Remote Handset Technical Page

This page currently holds all of my handset information.
As time allows, This will become a section of multiple pages.
For now, you'll have to scan through it.

UC1 of Handset

UC1-of-Handset Schematic
OOPS! schematic changed - R1, R3 = 10 ohm, not 100 ohm - Thanks Nigel

This board has the resposibility for RS232 and IR communications.

There is a crude voltage level translator on-board for the RS232.
RS232 signals operate in the range of -12v to +12.
The microcontroller operates at 0v and 5v.

For the IR, The IR detector has it's own switched supply rail and decoupling.
This is required to ensure no noise on the supply rail corrupts the signals.
The IR LED has a simple transistor switch.

This board seems to be a hub for the I2C channel.
The I2C clock and data from the UC3 links to:
  • The on-board micro - another SPMC02 from Sun-Plus
  • A connector for the eeprom PCB
  • A connector to UC2

Also, the speaker, AUDCTR, power and reset signal are passed through.

One observation - there is no power supply decoupling on this PCB.
One 220uF capacitor is present, but no low value (nF range) are present.

I will be monitoring the I2C bus soon, adding an eeprom and probing the RS232.
I'll also be checking out what the jumpers do.
Look out for updates.


The microcontroller used is encapsulated in a blob of resin.
This is known as Chip-On-Board (COB) technology.
The microcontroller is driven using a 32.768KHz crystal.
I have not investigated if a low battery detection is present.
This may be an internal peripheral of the microcontroller.

UC3-of-Handset Schematic


The LCD display has a resolution of 32 columns by 20 rows
This is electronically driven as 16 backplanes by 40 rows
I will include more info when I've drawn up the pictures
This will include the connections for the LCD panel.


The keys are scanned as a 4 x 3 matrix
This comprises of 3 outputs by 4 inputs.
During the 'ON' time, one output remains high via a resistor.
The other two are pulsed high for 30 microseconds every 30 milliseconds.
During 'OFF', all outputs are high, any keypress waking the micro.
Also during off, the micro is in a HALT state, with the crystal oscillator stopped.
This is to ensure maximum battery life.

A schematic of the keyboard matrix will be uploaded soon.

LEFT keypad Schematic
RIGHT keypad Schematic


The sound output seems to be a rough sampling method.
I will detail possible methods soon that may be similar to the one used here.


Nothing special to say here, apart from its poor performance.


The clock and data are the expected I2C lines.
When the unit is first powered, the microcontroller send out a broadcast.
I am about to check this out with the analyser.