Basic A/D question (newbie looking for help)

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Discussion Overview

The discussion revolves around a user's inquiry about interfacing an analog-to-digital (A/D) converter with a limited number of input/output (I/O) lines on a single board computer. The focus is on finding a suitable chip that can stream data over a single line while using another line for control, as well as exploring the options for serial versus parallel data transmission.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant describes a setup involving a data acquisition (DAQ) system and seeks a chip that can stream data over one line while using another for control, questioning how the control line should operate.
  • Another participant expresses uncertainty about the user's setup, asking for clarification on whether the A/D converter is a discrete chip or part of a card, and suggests that the user provide more details for better assistance.
  • A different participant mentions the need to use two data lines per A/D, proposing one as a control line and the other for data streaming.
  • One participant inquires about the specific A/D converters being used and whether they support serial interfaces like SPI or I2C, suggesting that a serial-to-parallel IO expander might be a solution if the A/Ds are only parallel.
  • Another participant lists several low-cost ADCs that utilize I2C and SPI protocols, asking for additional information about the user's application requirements such as sampling frequency, bandwidth, accuracy, power needs, and voltage levels to provide more tailored suggestions.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus, as there are multiple competing views on the best approach to interface the A/D converter, and the discussion remains unresolved regarding the specifics of the user's setup and requirements.

Contextual Notes

There are limitations in the information provided, including missing details about the specific A/D converters in use, their interface capabilities, and the user's exact application requirements, which may affect the feasibility of proposed solutions.

hertelbrian
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i'm a software guy trying to solve a little A/D problem i have...

i hve a daq that has a small number of I/O's and i have an A/D that i need to get data from. is there a chip in existence that can stream over one data line? my idea was to use one line to use as the data stream and the other line to step through the A/D value.

so if the output is 110101 i could change the state of a control line and when that state changes, the bit stream line would represent the next bit.

does this exist? and if so how does it work... does the control line listen for just a state change or only when it goes from low to high

thanks everyone in advnace!
 
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I'm not real clear on what you would like to do. It sounds like you have a DIO card for your PC with some number of digital IOs, and an A/D converter card also. And maybe a DAC card with an analog output capability too? Or is the ADC a discrete chip or board that you need to acquire data from to get it into your PC? And maybe your ADC chip has a parallel output that you want to serialize for some reason to get it into your PC via some DIO lines?

Maybe try painting the picture again so that we can help you understand your options.
 
what i have is a single board computer running linux. this is for an embedded systems application. the board has 8 I/Os on it and i need to use them sparingly i can hook up all 8 i/os to the A/D since i need to run 2 of them as well as a few other things...

so i was thinking use 2 data lines per A/D.. one as a control line and one as a data stream line..

any help is appreciated
 
What are the A/Ds? Do they have a serial interface mode like SPI or I2C? If they are only parallel (how wide? what interface?), then you might be able to use an SPI or I2C serial-to-parallel IO expander of some type to do what you want.
 
There are many low-cost ADCs which use I2C (a two-wire protocol) and SPI (generally a three-wire protocol).

Look into, for example, the AD7476, AD7477, and AD7478. If you want more specific suggestions, you will need to tell us some of following information about your application:

What sampling frequency, bandwidth, or accuracy (effective bits) do you need? Are there any power requirements? What voltages are you intending to sample? How fast can you toggle or read your I/O lines?

- Warren
 

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