UM0851 datasheet(186/245 Pages) STMICROELECTRONICS

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Human interface device (HID) drivers

UM0851

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Doc ID 16604 Rev 2

Block devices:

1 ramdisk

31 mtdblock

After obtaining the major number of the ADC, create ADC nodes using the following

commands:

mknod /dev/adcx c major x

/* Above command must be executed for x = 0 -> 7 */

These user level nodes may then be used for any further interaction with the ADC

driver/hardware.

Kernel level: Kernel modules must include drivers/char/spr_adc_st10.h file to access data

types related to the ADC. All kernel level calls expect the first argument to be a pointer

unique to the calling module. This pointer is kept in the ADC driver to track the owner of an

ADC channel.

In the following examples, ADC channel 0 is used as the configuring channel.

Open / get channel

To access any of the avaialble ADC features, you must acquire/get an ADC channel.

The channel can be opened using the open() call:

User level:

fd = open("/dev/adc0", O_RDWR);

On success, a positive file descriptor number is returned otherwise -1 is returned and errno

is set appropriately. This file descriptor is used for any further communication with the ADC

device.

Kernel level:

/* dev: pointer unique to the calling module */

spear_adc_chan_get(dev, ADC_CHANNEL0);

On success, zero is returned otherwise negative standard kernel errors are returned.

The above functions will be successful if the requested ADC channel is free and the ADC

device is not already being used in SINGLE_CONVERSION mode.

Configure ADC

Before converting data on an ADC channel, you must configure the ADC. There are two

types of configurations possible for the ADC.

●

Common configuration: This configuration is common to all ADC channels. It does

not have to be done every time you want to use the ADC. It must be configured keeping

in mind that it affects all ADC channels. During ADC module initialization, common

configuration is configured with the default configuration passed from the platform data

present in arch/arm/mach-spear*/spear*.c. This common configuration may not need to

be changed.

●

Channel configuration: this configuration is for a particular ADC channel.

ADC device configuration

UM0851 Datasheet(PDF) 186 Page - STMicroelectronics

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