1. ADC of AM335x

The internal ADC of AM335x is called TSC_ADC_SS (Touchscreen_ADC_subsystem), which is an 8 channel general purpose ADC, with optional support for interleaving Touch Screen conversions. The TSC_ADC_SS can be used and configured in one of the following application options:

8 general purpose ADC channels
4 wire TS, with 4 general purpose ADC channels
5 wire TS, with 3 general purpose ADC channels
8 wire TS

1.1 TSC_ADC properties

There are 7 analog inputs on the BeagleBone.

• ADC properties:
  • 12 bits (Output values in the range 0-4095)
  • 125ns sample time
  • 0-1.8V range (do not exceed!)
  • 2 uA current flows into the ADC pin in this range
  • If using a voltage divider, the lower leg (the one connected to ground) should be <= 1k Ohm
  • Since we are measuring millivolts, resistors with 0.1% error tolerance should be used in a voltage divider.
  • There is a 1.8V reference voltage VDD_ADC at Port 9 Pin 32.
  • There is a GNDA_ADC that should be grounded on Port9 Pin 34.

2 Connectivity

2.1 CM_WKUP_ADC_TSC_CLKCTRL

This register inside Control Module wakeup manages the clocks of ADC. As described in the definiation of CM_WKUP_ADC_TSC_CLKCTRL register default the CTRL is set to 0x0 which means Module is disable by SW. Any OCP access to module results in an error, except if resulting from a module wakeup (asynchronous wakeup). No clock no function