EmbeddedRelated.com
Forums
   Forums    More Forums    comp.arch.embedded  

LPC2138 AD converters

Started by Frank van Eijkelenburg ●June 18, 2008
Hi,

I am using a LPC2138 in my project. From this microcontroller I use
both AD converters. The problem I have:

channel 6 and 7 from AD0 are not working (I read the value 0 from the
ADC).

Other channels (0 to 4 of AD0) are working properly. Also AD1 is
working properly. I checked the PINSEL registers and these are
correct. What could cause the problem? Any ideas

TIA,
Frank
Reply by Frank van Eijkelenburg ●June 26, 20082008-06-26
On Jun 18, 4:22 pm, Frank van Eijkelenburg
<fei.technolut...@gmail.com> wrote:

> Hi,
>
> I am using a LPC2138 in my project. From this microcontroller I use
> both AD converters. The problem I have:
>
> channel 6 and 7 from AD0 are not working (I read the value 0 from the
> ADC).
>
> Other channels (0 to 4 of AD0) are working properly. Also AD1 is
> working properly. I checked the PINSEL registers and these are
> correct. What could cause the problem? Any ideas
>
> TIA,
> Frank


Solution was to pull P0.31 high during reset. According to the manual
a low signal on this pin during reset will disable JTAG (which I don't
use). According to the errata a low signal on this pin during reset
will result in undetermined device behavior.
Reply by emeb ●June 26, 20082008-06-26
On Jun 26, 6:43 am, Frank van Eijkelenburg
<fei.technolut...@gmail.com> wrote:

> On Jun 18, 4:22 pm, Frank van Eijkelenburg
>
> <fei.technolut...@gmail.com> wrote:
> > Hi,
>
> > I am using a LPC2138 in my project. From this microcontroller I use
> > both AD converters. The problem I have:
>
> > channel 6 and 7 from AD0 are not working (I read the value 0 from the
> > ADC).
>
> > Other channels (0 to 4 of AD0) are working properly. Also AD1 is
> > working properly. I checked the PINSEL registers and these are
> > correct. What could cause the problem? Any ideas
>
> > TIA,
> > Frank
>
> Solution was to pull P0.31 high during reset. According to the manual
> a low signal on this pin during reset will disable JTAG (which I don't
> use). According to the errata a low signal on this pin during reset
> will result in undetermined device behavior.


Thanks for the follow-up. That's a curious little bit of undocumented
behavior.

Eric