6 years, 1 month ago.

Is it posible to have more than one analog output with the mbed LPC1768?

Hello,

I've several questions:

-Is it posible to have more than one analog output with the mbed LPC1768? If it's not possible directly, is there any trick to do it if I have other components (for example, I was thinking to use 2 digital ouputs of the card to address another electronic component to manage the analog output flow of the mbed card. But I don't know what I need to buy to fo this) - Is it possible to use another pin than the p18 for the analog output? (when I did it, the compilation worked well but the card did not the job and the leds were flashing) - Is it possible to use more than one analog input in the same program (I need to use five analog inputs) ?

Thank you in advance for your answer,

Quentin

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2 Answers

6 years, 1 month ago.

You can use PWM to generate a voltage,

It only need a resistor & a capacitor,

but be aware, it is unlikely to supply current, without a buffer amp.

Ceri

6 years, 1 month ago.

You can use an analogue multiplexer (mux) see http://www.maximintegrated.com/products/switches/5v. With a 2 input mux, you would need one digital select line, 4 input mux, two digital lines etc. I frequently use an 8 input mux to generate 8 Analogue output lines.

Thank you Mike, I thought about that. But when I switch the mbed output to one of the outputs of the demultiplexer, I would like to keep the output voltage of the demultiplexer until the next change of value. I've this idea but I don't know if it will work: put an OPA and a capacitor after the output of the demultiplexer in order to supply something. Can you tell me if it's a good solution or if I need to do something else?

posted by Quentin Vinckier 20 Sep 2013

Hi Quentin, You could use a sample and hold device. See: http://www.ti.com/lit/ds/symlink/lf398-n.pdf

posted by mike egan 20 Sep 2013