TI_ADC(4) FreeBSD Kernel Interfaces Manual TI_ADC(4)


ti_adcTI AM3XXX analog to digital converter driver


device ti_adc


The ti_adc driver provides access to the AIN (analog inputs) on am3xxx SoCs.

It provides raw readings of the converted values for each analog inputs.

The access to ti_adc data is made via the sysctl(8) interface:

dev.ti_adc.0.%desc: TI ADC controller 
dev.ti_adc.0.%driver: ti_adc 
dev.ti_adc.0.%pnpinfo: name=adc@44E0D000 compat=ti,adc 
dev.ti_adc.0.%parent: simplebus0 
dev.ti_adc.0.clockdiv: 2400 
dev.ti_adc.0.ain.0.enable: 0 
dev.ti_adc.0.ain.0.open_delay: 0 
dev.ti_adc.0.ain.0.samples_avg: 0 
dev.ti_adc.0.ain.0.input: 0 
dev.ti_adc.0.ain.1.enable: 0 
dev.ti_adc.0.ain.1.open_delay: 0 
dev.ti_adc.0.ain.1.samples_avg: 0 
dev.ti_adc.0.ain.1.input: 0 
dev.ti_adc.0.ain.2.enable: 0 
dev.ti_adc.0.ain.2.open_delay: 0 
dev.ti_adc.0.ain.2.samples_avg: 0 
dev.ti_adc.0.ain.2.input: 0 
dev.ti_adc.0.ain.3.enable: 0 
dev.ti_adc.0.ain.3.open_delay: 0 
dev.ti_adc.0.ain.3.samples_avg: 0 
dev.ti_adc.0.ain.3.input: 0 
dev.ti_adc.0.ain.4.enable: 0 
dev.ti_adc.0.ain.4.open_delay: 0 
dev.ti_adc.0.ain.4.samples_avg: 0 
dev.ti_adc.0.ain.4.input: 0 
dev.ti_adc.0.ain.5.enable: 0 
dev.ti_adc.0.ain.5.open_delay: 0 
dev.ti_adc.0.ain.5.samples_avg: 0 
dev.ti_adc.0.ain.5.input: 0 
dev.ti_adc.0.ain.6.enable: 1 
dev.ti_adc.0.ain.6.open_delay: 0 
dev.ti_adc.0.ain.6.samples_avg: 4 
dev.ti_adc.0.ain.6.input: 2308 
dev.ti_adc.0.ain.7.enable: 1 
dev.ti_adc.0.ain.7.open_delay: 0 
dev.ti_adc.0.ain.7.samples_avg: 0 
dev.ti_adc.0.ain.7.input: 3812

On Beaglebone-black the analog input 7 is connected to the 3V3B rail through a voltage divisor (2:1). The 3V3B voltage rail comes from the TL5209 LDO regulator which is limited to 500mA maximum.

Global settings:

Sets the ADC clock prescaler. The minimum value is 10 and the maximum is 65535. The ADC clock is based on CLK_M_OSC (24Mhz) / clockdiv. This gives a maximum of ~2.4Mhz for the ADC clock and ~10Khz for the default setting (clockdiv = 2400).

Settings per input:

Enable the conversion for the input. Each input should be individually enabled before it can be used. When all the inputs are disabled, the ADC is turned off.
Sets the number of ADC clock cycles to wait after applying the input configuration and before start the ADC conversion.
Sets the number of samples average used on each input, it can be set to 0 (no samples average), 2, 4, 8, or 16.
Is the converted raw value of the voltage applied on the analog input. It is made of a 12 bit value (0 ~ 4095).




The ti_adc driver first appeared in FreeBSD 10.1.


The driver and this manual page was written by Luiz Otavio O Souza <loos@FreeBSD.org>.
June 1, 2014 FreeBSD