This article explains how to use the A/D converter lines on your Acme board
The A/D converter input lines are available on the following pins:
|3.3V||3.3 volt power line||J4.5||D14.1||D4.1||J6.1|
|AVDD||Clean 3.24V out for A/D circuitry||D14.2||D4.2||J6.33|
|VREF||A/D voltage reference input||W19||D14.3||D4.3||J6.34|
|AD0||Analog input 0||J4.34||W20||D14.5||D4.5||J6.30|
|AD1||Analog input 1||J4.36||W21||D14.6||D4.6||J6.29|
|AD2||Analog input 2||J4.38||W22||D14.7||D4.7||J6.28|
|AD3||Analog input 3||J4.40||W23||D14.8||D4.8||J6.27|
On Arietta G25 the VREF line is wired internally to the 3V3 volt so is not possible to change it.
By wiring the VREF pin to AVDD or VDD (max 3.3 volt) it's possible to read a max voltage of 3.24 volt with a resolution of 10 bit (1024 samples). In this way the max sample resolution we obtain is about 3.24V/1024 ~= 3mV.
On VREF no voltage higher than 3.3 Volt can be applied. If you need to read a higher signal use a schematic like this:
A module called DAISY-20 is available to use these lines in the range of 0 to 10 volts. Elsewhere use this schematic to test quickly the A/D lines:
A detailed description of the Atmel AT91 ADC driver used on the Kernel 3.xx is available on this page:
The AT91 ADC driver uses the Industrial Input/Output (IIO) subsystem described here:
If you are using a Kernel version 2.x instead of 3.x follow this article: Using A/D converter input lines with Kernel 2.x.
Front-end for the 4 channel A/D 10bits converter built-in the Atmel CPU.
Note: the daisy flat cable to wire this board is not included. Don't forget to buy it (code FLAT-20CM)
20 cm ribbon cable with 10 wires compatible with the Acme Daisy Cabling System.
At least one of these cables is required to connect each Daisy module.
if you need different lengths please consider making your own the cable using the IDC socket JJ-02291-10P-F and the flat cable FC-3754-1M.
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