AVR Freaks

Hi all thankyou for your responses its good to get some ideas and help.
I can feed anything as Im not unfamiliar with electronics and op amps but it is single ended 0-5v analogue and ttl rs232 levels. I already have a 422 converter.

Does anyone have any ideas on which ADC and example interfacing?
I seem to see that most 16 bit adcs with 4 inputs I have seen are differential inputs or single adcs.

i cant use parallel as I dont really have enough pins.
Im also not good at this really starting again after years so Im trying to find examples and keep it simple in blocks

Hi,
Its a project to read some sensor voltages on a remote submersible.i wrote the control stuff with a friend for a colledge project years ago and I now want to mount some sensors on it for bearing (nmea) sonar altitude (NMEA)and some depth, magnetic sensor, other sonar sensors.
bits were chosen to be able to navigate to within cm of an object in bad vis and to detect metal objects from analoigue out of a detector to a certain range and size. Its to do with an archaeological survey project.
Bits were just calculated from the number of divisions of volts needed to be sensed giving the number of bits per milivolt or microvolt and thus resolution of depth, range to all sides and magnetic tesla. I have tried with 8 bits and the sensitivity is very poor.
I have a working system on USB but I cant run that to 80m/100m.

Laying out the PCB is easy Im good at that and well versed at it. schematic is easy, Its the code Im not as good at. Yes time is running out this autumn to try it before sea conditions worsen.
I wanted to make a sonar capture system too.
2 16 bit adcs sampling after a trigger pulse for a specific time and at a specific selectable rate.
bits here defines dynamic range as above and while I can shife the foltages around I cant it then saturates and you dont know anythign other than you have a reading.

Thanks BobGardner, your help is much appreciated.

OK A spec for all interested.

*Im looking to use an Atmel Mega 128 wth a software UART or a larger processor with 4 UARTS.
*Id like to interface a MAX11060GUU+ 16 bit 4 wire spi instantaneous sampling ADC to it.
*Ill design the hardware so nothing needed. I have a kanda STK 20 and 300 to start development with a 422 converter on it.

Operation flow will be

On reception of a start command STAR ascii from UART 1
?read a $dbbt from UART 2 and a $ bearing string from UART 3(I only need bearing in degrees and depth in meters)
Read 4 16 bit samples from adc and add to the above commands in one string - my own mabe $test, Analog 1, Analogue 2 , Analogue 3, Analogue 4, Bearing, Depth
Stream up UART 1 to PC.

Do this 10 or 20 times a second.
Eevntually Id like to sample say 10 samples for each one and average them to improve my accuracy.

How is that for a basic spec?
Thanks again. Im using this as a learning exercise thats useful for projects but trying to get some data while th eweather on this site allows.

Wow I didnt expect that and so soon. Thanks. Ill see what you have done, Understanding it will be the hardest bit but most of it is simple c.
The SPI adc was the bit I was unsure of and how to get adc data from it.
The UART is standard which I understand the case structures I assume are for a state machine.
Your good... I am indeed so rusty Im needing more than a refresher.

Thanks BobGardner, I read all your code an dput my own together using what I learned from it.
I dont have a menu but I have got ports working etc.

Im strugglin gto get a display project working now but after checking all th ehardware there isnt much otehr than the difference between the 128 it was tested on and the 1280 that could cause problems.
Im talking to it in memory mapped mode and th ecode works ton the STK 300 dev kit just not my board. The LCD interface was copied to prove things work.