电子发烧友App

硬声App

0
  • 聊天消息
  • 系统消息
  • 评论与回复
登录后你可以
  • 下载海量资料
  • 学习在线课程
  • 观看技术视频
  • 写文章/发帖/加入社区
会员中心
创作中心

完善资料让更多小伙伴认识你,还能领取20积分哦,立即完善>

3天内不再提示
创作
电子发烧友网>电子资料下载>类型>参考设计>数字电位器Linux驱动程序

数字电位器Linux驱动程序

2021-04-21 | pdf | 191.09KB | 次下载 | 2积分

资料介绍

This version (05 Jan 2021 17:01) was approved by Ioana Chelaru.The Previously approved version (20 Nov 2015 16:36) is available.Diff

Digital Potentiometer Linux Driver

Supported Devices

Reference Circuits

Evaluation Boards

Description

The ad525x_dpot driver exports a simple sysfs interface. This allows you to work with the immediate resistance settings as well as update the saved startup settings. Access to the factory programmed tolerance is also provided, but interpretation of this settings is required by the end application according to the specific part in use.

Files

Each dpot device will have a set of eeprom, rdac, and tolerance files. How many depends on the actual part you have, as will the range of allowed values.

The eeprom files are used to program the startup value of the device.

The rdac files are used to program the immediate value of the device.

The tolerance files are the read-only factory programmed tolerance settings and may vary greatly on a part-by-part basis. For exact interpretation of this field, please consult the datasheet for your part. This is presented as a hex file for easier parsing.

Source Code

Status

Source Mainlined?
git Yes

Files

Example platform device initialization

For compile time configuration, it’s common Linux practice to keep board- and application-specific configuration out of the main driver file, instead putting it into the board support file.

For devices on custom boards, as typical of embedded and SoC-(system-on-chip) based hardware, Linux uses platform_data to point to board-specific structures describing devices and how they are connected to the SoC. This can include available ports, chip variants, preferred modes, default initialization, additional pin roles, and so on. This shrinks the board-support packages (BSPs) and minimizes board and application specific #ifdefs in drivers.

21 Oct 2010 16:10

Example Platform / Board file (I2C Interface)

Declaring I2C devices

Unlike PCI or USB devices, I2C devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each I2C bus segment, and what address these devices are using. For this reason, the kernel code must instantiate I2C devices explicitly. There are different ways to achieve this, depending on the context and requirements. However the most common method is to declare the I2C devices by bus number.

This method is appropriate when the I2C bus is a system bus, as in many embedded systems, wherein each I2C bus has a number which is known in advance. It is thus possible to pre-declare the I2C devices that inhabit this bus. This is done with an array of struct i2c_board_info, which is registered by calling i2c_register_board_info().

So, to enable such a driver one need only edit the board support file by adding an appropriate entry to i2c_board_info.

For more information see: Documentation/i2c/instantiating-devices

21 Oct 2010 16:10
static struct i2c_board_info __initdata bfin_i2c_board_info[] = {
#if defined(CONFIG_AD525X_DPOT) || defined(CONFIG_AD525X_DPOT_MODULE)
	{
		I2C_BOARD_INFO("ad5245", 0x2c),
	},
	{
		I2C_BOARD_INFO("ad5245", 0x2d),
	},
#endif
}

Example Platform / Board file (SPI Interface)

Declaring SPI slave devices

Unlike PCI or USB devices, SPI devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each SPI bus segment, and what slave selects these devices are using. For this reason, the kernel code must instantiate SPI devices explicitly. The most common method is to declare the SPI devices by bus number.

This method is appropriate when the SPI bus is a system bus, as in many embedded systems, wherein each SPI bus has a number which is known in advance. It is thus possible to pre-declare the SPI devices that inhabit this bus. This is done with an array of struct spi_board_info, which is registered by calling spi_register_board_info().

For more information see: Documentation/spi/spi-summary

21 Oct 2010 16:10
static struct spi_board_info bfin_spi_board_info[] __initdata = {
#if defined(CONFIG_AD525X_DPOT) || defined(CONFIG_AD525X_DPOT_MODULE)
	{
		.modalias = "ad5291",
		.max_speed_hz = 5000000,     /* max spi clock (SCK) speed in HZ */
		.bus_num = 0,
		.chip_select = 1,
	},
#endif
};

Old Method

static struct spi_board_info bfin_spi_board_info[] __initdata = {
#if defined(CONFIG_AD525X_DPOT) || defined(CONFIG_AD525X_DPOT_MODULE)
	{
		.modalias = "ad_dpot",
		.platform_data = "ad5291",
		.max_speed_hz = 5000000,     /* max spi clock (SCK) speed in HZ */
		.bus_num = 0,
		.chip_select = 1,
	},
#endif
};

Adding Linux driver support

Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)

The ad525x_dpot driver depends on CONFIG_SPI or CONFIG_I2C

Device Drivers  --->
  [*] Misc devices  --->
    <*>   Analog Devices Digital Potentiometers
    <*>     support I2C bus connection
    <*>     support SPI bus connection

Hardware configuration

PmodDPOT, ADSP-BF537 EZKIZ

Driver testing

Locate the device in your sysfs tree. This is probably easiest by going into the common i2c directory and locating the device by the i2c slave address.

 
	# ls /sys/bus/i2c/devices/
	0-0022  0-0027  0-002f
So assuming the device in question is on the first i2c bus and has the slave address of 0x2f, we descend (unrelated sysfs entries have been trimmed).

  
	# ls /sys/bus/i2c/devices/0-002f/
	eeprom0 rdac0 tolerance0
You can use simple reads/writes to access these files:

 
	# cd /sys/bus/i2c/devices/0-002f/
 
	# cat eeprom0
	0
	# echo 10 > eeprom0
	# cat eeprom0
	10
 
	# cat rdac0
	5
	# echo 3 > rdac0
	# cat rdac0
	3

More Information

下载该资料的人也在下载 下载该资料的人还在阅读
更多 >

评论

查看更多

下载排行

本周

  1. 1电子电路原理第七版PDF电子教材免费下载
  2. 0.00 MB  |  1491次下载  |  免费
  3. 2单片机典型实例介绍
  4. 18.19 MB  |  95次下载  |  1 积分
  5. 3S7-200PLC编程实例详细资料
  6. 1.17 MB  |  27次下载  |  1 积分
  7. 4笔记本电脑主板的元件识别和讲解说明
  8. 4.28 MB  |  18次下载  |  4 积分
  9. 5开关电源原理及各功能电路详解
  10. 0.38 MB  |  11次下载  |  免费
  11. 6100W短波放大电路图
  12. 0.05 MB  |  4次下载  |  3 积分
  13. 7基于单片机和 SG3525的程控开关电源设计
  14. 0.23 MB  |  4次下载  |  免费
  15. 8基于AT89C2051/4051单片机编程器的实验
  16. 0.11 MB  |  4次下载  |  免费

本月

  1. 1OrCAD10.5下载OrCAD10.5中文版软件
  2. 0.00 MB  |  234313次下载  |  免费
  3. 2PADS 9.0 2009最新版 -下载
  4. 0.00 MB  |  66304次下载  |  免费
  5. 3protel99下载protel99软件下载(中文版)
  6. 0.00 MB  |  51209次下载  |  免费
  7. 4LabView 8.0 专业版下载 (3CD完整版)
  8. 0.00 MB  |  51043次下载  |  免费
  9. 5555集成电路应用800例(新编版)
  10. 0.00 MB  |  33562次下载  |  免费
  11. 6接口电路图大全
  12. 未知  |  30320次下载  |  免费
  13. 7Multisim 10下载Multisim 10 中文版
  14. 0.00 MB  |  28588次下载  |  免费
  15. 8开关电源设计实例指南
  16. 未知  |  21539次下载  |  免费

总榜

  1. 1matlab软件下载入口
  2. 未知  |  935053次下载  |  免费
  3. 2protel99se软件下载(可英文版转中文版)
  4. 78.1 MB  |  537793次下载  |  免费
  5. 3MATLAB 7.1 下载 (含软件介绍)
  6. 未知  |  420026次下载  |  免费
  7. 4OrCAD10.5下载OrCAD10.5中文版软件
  8. 0.00 MB  |  234313次下载  |  免费
  9. 5Altium DXP2002下载入口
  10. 未知  |  233046次下载  |  免费
  11. 6电路仿真软件multisim 10.0免费下载
  12. 340992  |  191183次下载  |  免费
  13. 7十天学会AVR单片机与C语言视频教程 下载
  14. 158M  |  183277次下载  |  免费
  15. 8proe5.0野火版下载(中文版免费下载)
  16. 未知  |  138039次下载  |  免费