ADC max1027

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Instructions to install and use the onboard ADC (MAX1027)

Introduction

The MAX1027 is a 8 channels 10 bits A/D converter with integrated temperature sensor. The SPI1 interface is used to communicate with the device. Moreover, the max1027 is registered 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 !!) SPI Linux Config.png

Then select in Device Drivers->Hardware Monitoring Support->MAX1027 sensor chip (Module)

Once the new config saved, rebuild your image

# make

On the target, the driver can be started like this

# insmod /lib/modules/drivers/hwmon/hwmon.ko
# insmod /lib/modules/drivers/hwmon/max1027.ko

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