ADC Pi and Digital Sensors


3 posts
by 0x0000 » Thu Oct 31, 2013 11:19 am
Hello,
I am planning to connect both the Analog and Digital Sensors to my Raspberry Pi.
For Analog Sensors I have to use some kind of Analog to Digital Converter while for Digital Sensors I have to directly connect them to GPIO Pins.

Now,

I have bought this ADC Pi chip,

http://www.briandorey.com/post/ADC-Pi-R ... nline.aspx

If I connect all its pins to the Raspberry Pi, how then I will connect digital sensors , since all pins will be consumed by the ADC Pi ?
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by DavidS » Thu Oct 31, 2013 8:19 pm
You are aware that a simple resistor lader and a 74HC244 is all you need for a custome high speed flash ADC, then it is only a mater of the sampling speed being limited by your software. Be careful on the HW config for the intended voltage range. With something like this you should be able to get around 20MS/s on a stock RPi. Should be able to go much higher, though the limits provided by the way that the GPIO is wouted and a few other factors limit us to a reliable rate of around 50nanoseconds. There is little that can be done to fix that issue.

If you only need a 2-bit dac then this would only use 4 GPIO. A 3bit DAC would take 8 GPIO, and a 4bit would take 16 GPIO.
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by DeeJay » Thu Oct 31, 2013 9:10 pm
0x0000 wrote:I have bought this ADC Pi chip,

http://www.briandorey.com/post/ADC-Pi-R ... nline.aspx

If I connect all its pins to the Raspberry Pi, how then I will connect digital sensors , since all pins will be consumed by the ADC Pi ?


The pins are not all "consumed by the ADC."

If you look at the schematic here, you can see that in addition to power and ground only 2 signal lines are connected to the ADC board.

Since the ADC board has stackable headers, all the other gpio pins on the RPi P1 header remain accessible for other uses.
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