Shoot me in the right direction.

sccoupe

I am looking to monitor a 0-5vdc analog signal and send back out a 0-5vdc analog signal based on a lookup table. 8bit resolution would be fine. I was thinking of using a serial ADC into a propellor and then back out of a propellor to a serial DAC. Is this basically it? Would a BS1 be just as good to handle this? What part numbers for the 8bit dac/adc should I use? I am experimenting with different mass air meters in an automotive application and need to adjust the 0-5vdc signal before it goes to the engine computer. Any thoughts?

Thanks

Jason

Nick Mueller

> Is this basically it?

Yes.

> Would a BS1 be just as good to handle this?

Don't know about BasicStamp. But the task doesn't sound like needing a lot of MIPS.

> What part numbers for the 8bit dac/adc should I use?

Many examples if you search for ADC or have a look at the objectExchange. There you'll find ready made building blocks for some ADC/DACs for a quick start.

> Any thoughts?

Well, the Propeller is quite an overkill for that task. Except you want to serve many meters at a time.
Anyhow, it will work on the Propeller. And you could connect a laptop to your converter and change the translation table online.


Nick

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deSilva

All depends on your performance requirements (bandwidth), and - as Nick pointed out - the algorithmic complexity of your task. Being a "lookup table" only, I should say the Propeller as such is about 500 times too fast for it. Even if you use SPIN it will have ample spare capacity for any other task..

I generally recommend a low-cost I2C ADC/DAC (4 Channel, 8 Bit, 10 kHz, $3) PCF 8591.
This will take two I/O lines. What do plan to do with the other 30 I/O lines?

Rayman

You could also do ADC and DAC directly with the Prop using 3 pins. Inputing 0 to 5 V is no problem. But, you'd need to boost the output from 3.3V up to 5V... Still, this could be done with one 5V rail-to-rail opamp...

Rayman

Another option for the output might be a digital pot. How well this would work probably depends on the output impedance you need. If the auto has a high enough input impedance, you should find a digital pot that can give you the output you need.

With that said, I'd probably recommend the I2C route that deSilva mentioned for overall simplicity...