Hi Rauf,

I prefer also external ADC / DAC, since on a single chip, the digital section (CPU) can cause a lot of noise on the analog section.

Yes, you can use the CA3162. Then you need 6 lines to the micro.

With a multiplexer (e.g. 74HCT4051) you can select up to 8 inputs.

To convert 20mA to a voltage only a resistor was needed.

E.g. for the CA3162 input range of 1V you need:
1V / 20mA = 50R.

But you can use many others ADC. Some have already a multiplexer build in.
Ask your local salesman, which is available and cheap.

To reduce the connections to the micro, I suggest ADC with serial interface (e.g. SPI or I2C).

For display output I suggest also serial interfaces for easy wiring.
See at:
http://www.specs.de/~danni/ap.../index.htm
or:
http://www.specs.de/~danni/ap...ax7219.htm

To make the calculations easy, I suggest programming in C.
I think, it should fit into the 2kB of the AT89C2051.
So you can use the Keil evaluation version.
Don't worry about linking at 4000h, since the AT89C2051 ignores the upper address bits.


Peter