Help me create circuit that transmit values of 4 ADCs to a serial port

[thief_]

I'm looking for a circuit which will take the 12-bit output of an ADC and pump it down a serial cable to the PC.

What I then want to do is add another 3 more ADCs to the circuit. My aim is to transmit the values of the 4 ADCs down the serial cable as a continous stream in the following manner:

C1
XX1
YY1
C2
XX2
YY2
C3
XX3
YY3
C4
XX4
YY4

This "black box" will be used to convert 4 analogue signals (Channels) to digital values. It seems that there must not be too many ppl out there who know how to do this as I have not had any success in finding this information.

Regards

Thief_

 

[FoxyRick]

Re: ADC to Serial port

If you want to use a PIC, it's about as easy as it gets.

A PIC16C771 has 6 lines of 12-bit ADC and you could bit-bang the serial out, but it's a bit old.

The dsPIC30F2011 has 8 lines of 12-bit ADC and a UART to make the serial easier. Should be trivial to do it with this one, even if you've never programmed a PIC before.

Many other MCU's could do the same. Another alternative is a cheaper PIC connected to a quad ADC, again there are *many* to choose from.

You could even do it just with the ADC, a UART and some timing and glue logic, but it would probably end more complicated, bigger and costlier.

Trust me, there are *plenty* of people who know how to do this, you need to decide on exactly what you want (sampling rate, simultaneous or multiplexed sampling, signal conditioning etc) then decide which of the above methods is most appropriate, then try to implement it, at least on paper. People can help you more when you know how you want to acheive your goals.

A final thought: you could do it with just a ADC and a bit of logic, if you used the parallel port to control it all.

For some good ADC's, check these places:

**broken link removed**
**broken link removed**

Cheers,
FoxyRick.

 

[thief_]

Re: ADC to Serial port

Thanks FoxyRick,

I'm looking at using the **broken link removed**ADC which has 4 integrated analog inputs.

My question is, although the chip presents the data of each ADC to the PC's serial port, how will my application running on the PC know which port the data is referring to?

Looks like I'm going to have to find another chip which has a single ADC and a parallel digital output of 12 bits. Then hardwire 4 bits at the start othe 12 data bits to signal which port that particular ADC's data refers to.

Can anyone suggest a circuit which will take the 12 + 4 bits and serialise them? THANKS!

 

[thief_]

Re: ADC to Serial port

* BUMP *
?????????

 

[electronrancher]

Re: ADC to Serial port

i'd use the dspic, it already has a 12-bit adc muxed to 8 channels. write a routine that sends a two byte code to signal the start of a frame, then send the 16-bit channel + data info you described. let the uart take care of all the framing, etc - much easier than trying to glue-logic a discrete UART to a parallel out ADC.

PS - other than your 4 input pins, what part of this is analog? you should probably move this thread to digital or microcontroller.

 

[hifni]

Re: ADC to Serial port

for transmitting 12 bit data via serial port you can try with designing the communication protocol...
example :
You can build the protocol with frame of data in serial comm, just like :

command : frame1=address of ADC
frame2=command
frame3=parameter1

answer from serial device :
frame1=id of answering device
frame2=answer1 (first byte ADC data)
frame2=answer2 (second byte ADC data)

Above just an example of serial communication protocol... You can design it on your own isn't it?

se ya!