Basic A/D question (newbie looking for help)

  • Thread starter hertelbrian
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In summary, the conversation is about a software guy trying to solve an A/D problem with a limited number of I/Os. They are discussing the possibility of using a chip that can stream data over one line to simplify the process. There are suggestions for using an ADC with a serial interface or an SPI or I2C serial-to-parallel IO expander. The conversation ends with a recommendation to look into low-cost ADCs such as the AD7476, AD7477, and AD7478, but more specific information about the application is needed.
  • #1
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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  • #2
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.
 
  • #3
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
 
  • #4
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.
 
  • #5
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
 

What is A/D conversion and why is it important?

A/D conversion, or analog-to-digital conversion, is the process of converting analog signals into digital signals. This is important because most modern electronic devices, such as computers and smartphones, use digital signals to process and transmit information. A/D conversion is necessary to convert the analog signals from the physical world (such as sound or temperature) into digital signals that can be understood and processed by these devices.

What is the difference between analog and digital signals?

An analog signal is continuous and has an infinite number of possible values. Examples of analog signals include sound waves and temperature readings. On the other hand, a digital signal is discrete and has a limited number of possible values. It is represented by binary digits (bits) of 0s and 1s. Digital signals are used in electronic devices because they are easier to manipulate and transmit, and they are less susceptible to noise and interference.

How does an A/D converter work?

An A/D converter works by sampling an analog signal at regular intervals and measuring its amplitude (or voltage) at each sample point. The amplitude is then converted into a digital value using a binary code, typically through a process called quantization. The resulting digital signal can then be processed by a microcontroller or computer.

What are the common types of A/D converters?

There are several types of A/D converters, including successive approximation, delta-sigma, dual slope, and flash. Each type has its own advantages and disadvantages, and the choice of which type to use depends on the specific application. For example, successive approximation converters are commonly used in microcontrollers, while flash converters are used in high-speed applications such as data acquisition systems.

How can I improve the accuracy of my A/D conversion?

There are several ways to improve the accuracy of an A/D conversion, including using a higher-resolution converter, using a low-pass filter to reduce noise, and using a stable power supply. It is also important to properly calibrate the A/D converter and compensate for any non-linearities. Additionally, the sampling rate and input signal range should be carefully considered for optimal accuracy.

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