LouiseC LouiseC

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9 years, 10 months ago.

How to use the CAN ?

I would like to receive a voltage from 0 to 5V and then display it on the LCD screen. I can not use Analogin because they are used ​​by the lcd screen. So I would use pine 27, 28, 29, 30 of mbed NXP LPC1768. How?

Thank you

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Last updated: 30 Apr 2020

1 Answer

David Smart
9 years, 9 months ago.

You have a difficult challenge here. On the mbed, I think [nearly] every pin can be configured as DigitalIn or DigitalOut, but there are only a few that can be an AnalogIn.

The best recommendation is to move the display to other pins, in order to free the AnalogIn to measure the voltages.

Side note: The mbed can measure from 0 to 3.3v. Placing 5v on the pin is damaging. So, you will need to reduce the 5v down to 3.3v with a voltage divider (for example something a bit higher than 17K from your signal to the AnalogIn and then 33K from there to ground).

If you cannot move the display pins, there are a number of more complex possibilities for measuring an analog input.

  • Use another mbed (or other controller), connected via CAN or the Serial Port (on your referenced pins 27,28 or 29,30).
  • Use an external A/D converter, perhaps wired to these same pins.
  • Use an external voltage to frequency converter and then measure the frequency.

These create more complex solutions to your challenge. But for each you can search the web to find information and help to move your design forward.

Accepted Answer