ADC Test & Analog Mode

[lpcware]

Content originally posted in LPCWare by woodchuck on Fri Nov 30 15:38:21 MST 2012
In the LPCXpresso library for the LPC1114, there is an ADC.C file.  In the initialization function there is this comment:

[B]"Unlike some other pings, for ADC test, all the pins need to [be] set to analog mode."[/B]

Would anyone know what this means?  Even in the sample program, AD4 is being used as SWDIO, since the target uC is reporting values back to the host via JTAG.

I certainly hope it doesn't mean that to use any analog line, you have to use all of them!

[lpcware]

Content originally posted in LPCWare by woodchuck on Sat Dec 01 11:51:11 MST 2012
Okay.  I see.  ADC_TEST actually reads all available ADC lines.  That's why all are enabled.  I read too much into the comment that "...[B][I]all[/I][/B] pins [B][I]need to be[/I][/B] set..." as though it pertained to any use whatsoever of the ADC facility.

Thanks!

[lpcware]

Content originally posted in LPCWare by graynomad on Fri Nov 30 16:40:36 MST 2012

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Quote:
I certainly hope it doesn't mean that to use any analog line, you have to use all of them!

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No, you have to select the analogue function in the IOCON register for the pin you want to use analogue on.

On the 1227 that means clearing bit 7.

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Fri Nov 30 15:53:49 MST 2012
UM:

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Quote:

The ADC function must be selected via the IOCON registers in order to get accurate voltage readings on the monitored pin. For a pin hosting an ADC input, it is not possible to have a have a digital function selected and yet get valid ADC readings. An inside circuit disconnects ADC hardware from the associated pin whenever a digital function is selected on that pin.

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Of course you can switch each pin to ADC :eek: