Difference between revisions of "LRADC"
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This description uses Linux kernel > 3.7. | This description uses Linux kernel > 3.7. | ||
| − | LRADC is a 12 bits 16 channels Analog to Digital Converter integrated into the | + | LRADC is a 12 bits 16 channels Analog to Digital Converter integrated into the i.MX28 processor. |
| − | Only channels 0-6 may be used to generic conversions and channels 2, 3, 4, 5 are used | + | Only channels 0-6 may be used to generic conversions and channels 2, 3, 4, 5 are used for the touchscreen on [[APF28Dev]]. |
| − | * Channel 0 is available on | + | * Channel 0 is available on J10 pin 38 of [[APF28Dev]] |
| − | * Channel 1 is available on | + | * Channel 1 is available on J10 pin 36 of [[APF28Dev]] |
| − | * Channel 6 is available on | + | * Channel 6 is available on J10 pin 35 of [[APF28Dev]] |
== Driver == | == Driver == | ||
| Line 36: | Line 36: | ||
=== Load driver === | === Load driver === | ||
| − | To use the LRADC, first load ''lradc'' module: | + | To use the LRADC, first load ''mxs-lradc'' module: |
<pre class="apf"> | <pre class="apf"> | ||
| Line 55: | Line 55: | ||
</pre> | </pre> | ||
| − | To read | + | To read ADC value just «cat» the corresponding input file: |
<pre class="apf"> | <pre class="apf"> | ||
| − | # cat in_voltage0_raw | + | # cat in_voltage0_raw for channel 0 |
4095 | 4095 | ||
</pre> | </pre> | ||
| − | All values are not converted (ie. directly the register content). To have the mV value, you must | + | All values are not converted (ie. directly show the register content). To have the mV value, you must do: value_mV = in_voltageX_raw * 1850/4095 |
| + | |||
| + | ===Temperature=== | ||
| + | * LRADC is also able to give us i.MX28 die temp: | ||
| + | |||
| + | <pre class="apf"> | ||
| + | TEMP_RAW=`cat /sys/bus/iio/devices/iio:device0/in_temp8_raw` | ||
| + | TEMP_OFFSET=`cat /sys/bus/iio/devices/iio:device0/in_temp8_offset` | ||
| + | TEMP_SCALE=`cat /sys/bus/iio/devices/iio:device0/in_temp8_scale` | ||
| + | |||
| + | TEMP=`echo "${TEMP_RAW} ${TEMP_OFFSET} + ${TEMP_SCALE} * p" | dc` | ||
| + | echo ${TEMP} | ||
| + | </pre> | ||
| + | |||
| + | ==Links== | ||
| + | * http://www.at91.com/linux4sam/bin/view/Linux4SAM/IioAdcDriver | ||
[[Category:Linux drivers]] | [[Category:Linux drivers]] | ||
[[Category:Analog to Digital Converter]] | [[Category:Analog to Digital Converter]] | ||
| + | [[Category:Industrial Input Output]] | ||
Latest revision as of 15:15, 25 November 2019
Contents
Introduction
This description uses Linux kernel > 3.7.
LRADC is a 12 bits 16 channels Analog to Digital Converter integrated into the i.MX28 processor.
Only channels 0-6 may be used to generic conversions and channels 2, 3, 4, 5 are used for the touchscreen on APF28Dev.
- Channel 0 is available on J10 pin 38 of APF28Dev
- Channel 1 is available on J10 pin 36 of APF28Dev
- Channel 6 is available on J10 pin 35 of APF28Dev
Driver
Driver is by default included if you choose an APF28 as target.
Otherwise, you can select it that way:
[ ] $ make linux-menuconfig
Device Drivers --->
<M> Staging drivers --->
IIO staging drivers
Analog to digital converters
<M> Freescale i.MX28 LRADC
Then compile the distribution :
[ ] $ make linux && make
Use it
Load driver
To use the LRADC, first load mxs-lradc module:
# modprobe mxs-lradc
Read channels value
# cd /sys/bus/iio/devices/iio:device0 # ls buffer in_voltage11_raw in_voltage2_raw name dev in_voltage12_raw in_voltage3_raw power in_temp8_raw in_voltage13_raw in_voltage4_raw scan_elements in_temp9_raw in_voltage14_raw in_voltage5_raw subsystem in_voltage0_raw in_voltage15_raw in_voltage6_raw trigger in_voltage10_raw in_voltage1_raw in_voltage7_raw uevent
To read ADC value just «cat» the corresponding input file:
# cat in_voltage0_raw for channel 0 4095
All values are not converted (ie. directly show the register content). To have the mV value, you must do: value_mV = in_voltageX_raw * 1850/4095
Temperature
- LRADC is also able to give us i.MX28 die temp:
TEMP_RAW=`cat /sys/bus/iio/devices/iio:device0/in_temp8_raw`
TEMP_OFFSET=`cat /sys/bus/iio/devices/iio:device0/in_temp8_offset`
TEMP_SCALE=`cat /sys/bus/iio/devices/iio:device0/in_temp8_scale`
TEMP=`echo "${TEMP_RAW} ${TEMP_OFFSET} + ${TEMP_SCALE} * p" | dc`
echo ${TEMP}
