![Character Driver
Struct File_Operator
read()
write()
Ioctl()
open
release()
cat /dev/lis3dh
Code Snippet for Read:
//X_L (28h)
g_sensor[0]=i2c_smbus_read_byte_data
(client,0x28);
//X_H(29h)
g_sensor[1]=i2c_smbus_read_byte_data
(client, 0x29);
x = (short) (g_sensor[0] | (((unsigned
short)g_sensor[1]) << 8));](https://image.slidesharecdn.com/smbus2linuxdriverforstmicrolis3dh-181016035414/85/Linux-Driver-Pi-Linux-Driver-for-STMicro-LIS3DH-10-320.jpg)
實作Linux Driver移植在樹莓 Pi上：Linux Driver for STMicro LIS3DH
- 1. Linux Driver for STMicro LIS3DH 演講:秦O航
- 2. Outline Linux Kernel Driver 實作 G-sensor 應用及原理 G-sensor 電路實作 i2c protocol Demo實作
- 6. Circuit Pi LIS3DH Pi I2C interface SDA SCL
- 7. Procedure for Linux Driver for LIS3DH LIS3DH I2C Driver Character Driver /dev/lis3dh cat /dev/lis3dh gsensor@19{ compatible = "lis3dh"; reg = <0x19>; }; Device Tree User Application lis3dh.ko lis3dh.dtbo1 2 3
- 8. Add I2C Driver struct I2c_driver lis3dh_driver Probe lis3dh_init register char remove unregister char del_i2c_driver module_i2c_driver (lis3dh_driver)
- 9. Describe a node in Device Tree /boot/overlays/ lis3dh.dtbo DT compiler Lis3dh.dts gsensor@19{ compatible = "lis3dh"; reg = <0x19>; }; Device Tree
- 10. Character Driver Struct File_Operator read() write() Ioctl() open release() cat /dev/lis3dh Code Snippet for Read: //X_L (28h) g_sensor[0]=i2c_smbus_read_byte_data (client,0x28); //X_H(29h) g_sensor[1]=i2c_smbus_read_byte_data (client, 0x29); x = (short) (g_sensor[0] | (((unsigned short)g_sensor[1]) << 8));
- 11. i2c Operation 讀寫 1) Write: 需要1個I2C Message 2) Read: 需要2個I2C Message (會有2個START) 資料長度 1) Byte (8 bit) 2) Word (16 bit) 3) Block (multi-byte , at most 32 bytes)
- 13. Read/Write Example addr flags I2C Read example (2個 i2c_msg) I2C Write example (1個 i2c_msg) 每一次的START就要包裝成一個i2c message, 然後用i2c_transfer()去送, i2c_transfer()送完後就是STOP狀態
- 14. Linux I2C Client API //Write送出2個byte: <SA+’flag’> <value> s32 i2c_smbus_write_byte (const struct i2c_client *client, u8 value) s32 i2c_smbus_read_byte (const struct i2c_client *client) //Write送出3個byte: <SA+’flag’> <cmd> <value> s32 i2c_smbus_write_byte_data(const struct i2c_client *client, u8 command,u8 value) s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command) //Write送出4個byte: <SA+’flag’> <cmd> <value> <value> s32 i2c_smbus_write_word_data (const struct i2c_client *client, u8 command,u16 value) s32 i2c_smbus_read_word_data (const struct i2c_client *client, u8 command) //Write送出n個byte: <SA+’flag’> <cmd> <value> <value> …….<value> s32 i2c_smbus_write_block_data (const struct i2c_client *client, u8 command, u8 length, const u8 *values) s32 i2c_smbus_read_block_data (const struct i2c_client *client, u8 command,u8 length, u8 *values)
- 17. Protocol for LIS3DH An 8-bit sub-address (SUB) is transmitted: the 7 LSB represent the actual register address while the MSB enables address auto increment. If the MSB of the SUB field is ‘1’, the SUB (register address) is automatically increased to allow multiple data read/writes. 17
- 18. Protocol for LIS3DH 18 MAK is Master acknowledge and NMAK is No Master Acknowledge SUB address
- 21. Demo
- 22. References LinuxDeviceDriver Programming驅動程式設計 博碩文化出版 解析Linux驅動程式設計MMC/SD、USB、 I2C、PCI網路及輸入裝置等 博碩文化出版 ITTRAINING輸出入裝置與驅動程式設計 艾鍗學院出版 王者歸來Linux驅動程式開發權威指南 佳魁出版