Difference between revisions of "ADC max1027"

From ArmadeusWiki
Jump to: navigation, search
(Hardware)
(Usage)
Line 42: Line 42:
  
 
==Usage==
 
==Usage==
Several interfaces in ''/sys/bus/spi/devices/'' are created in order to:
+
==="Slow" interface (for temperature or battery level measurements)===
 +
Several interfaces in ''/sys/bus/spi/devices/spi...'' are created in order to:
 
* read the 8 inputs (inx_input). Result in mV
 
* read the 8 inputs (inx_input). Result in mV
 
* read the temperature (temp_input). Result in deg celsius
 
* read the temperature (temp_input). Result in deg celsius
 
* modify the default configuration (config and conv)
 
* modify the default configuration (config and conv)
  
An input can be read like that
+
An input can be read like that:
 
  # cat /sys/bus/spi/devices/spi1.0/in0_input
 
  # cat /sys/bus/spi/devices/spi1.0/in0_input
  
The temperature can be read like that
+
The temperature can be read like that:
 
  # cat /sys/bus/spi/devices/spi1.0/temp1_input
 
  # cat /sys/bus/spi/devices/spi1.0/temp1_input
  
The two configurations files allow direct access to the corresponding register in the MAX1027:
+
'''These values are only update once every 10 ms and are only dedicated to measure slow evolving greats.'''
 +
 
 +
==="Fast" interface (frequencies > 10Hz)===
 +
In that case you can use /dev interface (using blocking read to wait end of conversion). To create ''/dev'' nodes you can use the ''loadmax.sh'' script. As driver MAJOR number is dynamically allocated, you may need to update ''/dev'' depending on the drivers loaded on you system.
 +
 
 +
* repeatedly read value of input 0 (variable sampling rate = depends on system load):
 +
# cat /dev/max1027/AIN0
 +
* read input 0 once:
 +
# time dd if=/dev/max1027/AIN0 bs=2 count=1 > tmp.bin
 +
# hexdump tmp.bin
 +
 
 +
===Chip registers configuration===
 +
Independent of the mode, ''/sys'' interfaces allow direct access to the corresponding register in the MAX1027:
 
  # let conv=0xb9; echo $conv > /sys/bus/spi/devices/spi1.0/conversion
 
  # let conv=0xb9; echo $conv > /sys/bus/spi/devices/spi1.0/conversion
  
For more details, take a look at the datasheet.
+
You can also get current values of conversion, averaging and setup register with:
 +
# cat /sys/bus/spi/devices/spi1.0/setup
 +
0x62
 +
 
 +
For more details on how to use these registers, take a look at the datasheet.
  
 
==Links==
 
==Links==

Revision as of 18:53, 8 September 2008

Instructions to install and use the MAX1027 ADC. This device is an option of the APF9328 boards. To know if you have one on your board, take a look at the connectors side:

APF9328 with MAX1027.jpg

If you don't have one and are a good electronician, you can order a sample at Maxim's website and solder it directly on your board (footprint is available).

Introduction

The Max1027 is an 8 channels 10 bits A/D converter with an integrated temperature sensor.

Hardware

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.
MAX1027 connections.png

If you want to use MAX1027 in "fast" mode (ie measure signals with frequencies > 10 Hz) then you will have to connect #EOC pin (End Of Conversion) to an i.MXL GPIO, configured as Interrupt (see apf9328.c for more details).

Driver

For the Linux kernel, the Max1027 is considered as a Hardware Monitoring 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)

HWMonitor Linux Config.png

MAX1027 Linux Config.png

  • 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

"Slow" interface (for temperature or battery level measurements)

Several interfaces in /sys/bus/spi/devices/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/devices/spi1.0/in0_input

The temperature can be read like that:

# cat /sys/bus/spi/devices/spi1.0/temp1_input

These values are only update once every 10 ms and are only dedicated to measure slow evolving greats.

"Fast" interface (frequencies > 10Hz)

In that case you can use /dev interface (using blocking read to wait end of conversion). To create /dev nodes you can use the loadmax.sh script. As driver MAJOR number is dynamically allocated, you may need to update /dev depending on the drivers loaded on you system.

  • repeatedly read value of input 0 (variable sampling rate = depends on system load):
# cat /dev/max1027/AIN0
  • read input 0 once:
# time dd if=/dev/max1027/AIN0 bs=2 count=1 > tmp.bin
# hexdump tmp.bin

Chip registers configuration

Independent of the mode, /sys interfaces allow direct access to the corresponding register in the MAX1027:

# let conv=0xb9; echo $conv > /sys/bus/spi/devices/spi1.0/conversion

You can also get current values of conversion, averaging and setup register with:

# cat /sys/bus/spi/devices/spi1.0/setup
0x62

For more details on how to use these registers, take a look at the datasheet.

Links

Other languages:

English Flag.svg English  •  French Flag.svg Français