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.\" Copyright (c) 2014 Luiz Otavio O Souza <loos@freebsd.org>
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.Dd June 1, 2014
.Dt TI_ADC 4
.Os
.Sh NAME
.Nm ti_adc
.Nd TI AM3XXX analog to digital converter driver
.Sh SYNOPSIS
.Cd "device ti_adc"
.Sh DESCRIPTION
The
.Nm
driver provides access to the AIN (analog inputs) on am3xxx SoCs.
.Pp
It provides raw readings of the converted values for each analog inputs.
.Pp
The access to
.Nm
data is made via the
.Xr sysctl 8
interface:
.Bd -literal
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
.Ed
.Pp
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.
.Pp
Global settings:
.Bl -tag -width ".Va dev.ti_adc.0.clockdiv"
.It Va dev.ti_adc.0.clockdiv
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).
.El
.Pp
Settings per input:
.Bl -tag -width ".Va dev.ti_adc.0.ain.%d.samples_avg"
.It Va dev.ti_adc.0.ain.%d.enable
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.
.It Va dev.ti_adc.0.ain.%d.open_delay
Sets the number of ADC clock cycles to wait after applying the input
configuration and before start the ADC conversion.
.It Va dev.ti_adc.0.ain.%d.samples_avg
Sets the number of samples average used on each input, it can be set to 0
(no samples average), 2, 4, 8, or 16.
.It Va dev.ti_adc.0.ain.%d.input
Is the converted raw value of the voltage applied on the analog input.
It is made of a 12 bit value (0 ~ 4095).
.El
.Sh SEE ALSO
.Xr sysctl 8
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 10.1 .
.Sh AUTHORS
.An -nosplit
The driver and this manual page was written by
.An Luiz Otavio O Souza Aq Mt loos@FreeBSD.org .