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Update for 15-11-21 16:00

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Tyler Perkins 2021-11-15 16:00:01 -05:00
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@ -236,4 +236,34 @@ NOTE to help with calculations, 0xFFFF is 65536 and 0xFF is 256
| 256 | 62500 |
| 1024 | 15625 |
=== Analog to Digital ===
The ATMega328P includes an [[ADC]] for reading analog inputs. The ADC, like
everything else, is controlled via several control registers.
The primary control register is the ADC Multiplexer Selection Register (ADMUX
0x7C). Bit 7 and 6 select the reference voltage for the ADC. Any updates to
this register do not take effect till after an ongoing ADC operations has
completed. The internal voltage reference may not be used if a voltage is
applied across the AREF pin. Below are valid values for bits 7 and 6
| Bits (7-6) | Description |
----------------------------
| 00 | AREF, internal reference voltage turned off |
| 01 | AV,,cc,,, with an external capactior on AREF |
| 10 | Reserved (non functioning) |
| 11 | Internal 1.1V reference used with capactior on AREF |
Bit 5 of ADMUX changes the presentation of the ADC result, and when set to one
(1) the value will be left adjusted, otherwise it will be right adjusted. This
change happens instantly, regardless of the actions in the ADC
Bits 3-0 set which ADC pin will be converted (NOTE these are the pins on PortC
on the Arduino Nano). For values 0 through 7 (binary values in bits 3-0), will
select the corresponding ADC pin. 0b1000 is a sepcial ADC, connected to the
internal temperture sensor. 0b1110 (10d14) is the internal reference voltage of
1.1V, and 0b1111 (10d15) is internal reference GND (0V). All non mentioned
values are not used
To control the ADC, the ADC control and Status Register A (ADCSRA 0x7A) and ADC
Control and Status Register B (ADCSRB 0x7B) are used.