ADC max1027
Instructions to install and use the onboard ADC (MAX1027)
Introduction
The Max1027 is a 8 channels 10 bits A/D converter with an integrated temperature sensor.
The 8 inputs voltage range is 0 - 3,3V. Don't try to put higher voltage on ADC inputs !!
The i.MXL SPI_1 interface is used to communicate with the device.
For the Linux kernel, the Max1027 is considered as a hardware monitor device.
For the moment only a low speed interface (/sys) is available: the eight channels and the temperature are updated every 10ms.
Installation
From the top directory:
# make linux-menuconfig
Then select in Device Drivers->SPI support->Freescale iMX SPI controler driver (builtin not module !!)
Then select in Device Drivers->Hardware Monitoring Support->MAX1027 sensor chip (Module)
Once the new config saved, rebuild your image
# make
and copy hwmon.ko and max1027.ko driver to your target or reflash your rootfs.
On the target, the driver can be started like this:
# insmod /lib/modules/drivers/hwmon/hwmon.ko # insmod /lib/modules/drivers/hwmon/max1027.ko
or like this if you reflashed your rootfs:
# modprobe max1027
Usage
Several interfaces in /sys/bus/spi/are created in order to
- read the 8 inputs (inx_input). Result in mV
- read the temperature (temp_input). Result in deg celsius
- modify the default configuration (config and conv)
An input can be read like that
# cat /sys/bus/spi/drivers/max1027/spi1.0/in0_input
The temperature can be read like that
# cat /sys/bus/spi/drivers/max1027/spi1.0/temp1_input
The two configurations files allow direct access to the corresponding register in the MAX1027. For more details, take a look at the datasheet
