analogRead doesn't allow to read all channels

[arnakke]

Currently wiring_analog.c only allows to read channel 0 through 7. However, the internal temperature sensor is located on channel 8.

Fix. Change line 69 in wiring_analog.c
From:
ADMUX = (analog_reference << 6) | (pin & 0x07);
To:
ADMUX = (analog_reference << 6) | (pin & 0x0F);

This will allow to read all channels without any drawbacks as far a I can tell.

[EternityForest]

We also need to define a constant so you can say

x = analogRead(INTERNAL_TEMP);

or such.

Are there any processors that use bit 4 of ADMUX for something besides channel selection? I don't know of any but I don't do a lot of AVR work.

[EternityForest]

This patch was implemented in 0017 but broke something. This is useful enough on account of the fact that you can generate random seeds from temp even when all IO is used, and the fact that there are other ADC channels(like the internal reference) that we might want to measure.

This needs a compile time switch to detect what avr is being used, and constants for the temp sense channel that are board specific.

Relevant thread:http://forum.arduino.cc/index.php/topic,38043.0.html#14