Linux（I2C）

格式

i2c 分兩種格式: 7bit & 10bit

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(M) = Master to Slave
(S) = Slave  to Master
# Write 格式
S(M) + Slave Address(M) + W = 0(M) + A(S) + DATA(M) + A(S) + DATA(M) + A(S) + P(M)

# Read 格式
S(M) + Slave Address(M) + R = 1(M) + A(S) + DATA(S) + A(M) + DATA(S) + A(M) + P(M)

C example

要先 include 

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int file;
int adapter_nr = 2; /* Bus-2 可動態決定 */
char filename[20];
  
snprintf(filename, 19, "/dev/i2c-%d", adapter_nr); /* 打開 /dev/i2c-2 */
file = open(filename, O_RDWR);
if (file < 0) {
    exit(1);
}

/* 設定要 R/W 的 Device Address */
int addr = 0x40; /* The I2C address */  
if (ioctl(file, I2C_SLAVE, addr) < 0) {      
  exit(1);
}    

/* 設定要 R/W Device 的哪一個 register */
__u8    reg = 0x10; /* Device register to access */
__s32   res;
char    buf[10];
  

res = i2c_smbus_read_word_data(file, reg);
if (res < 0) {
  /* ERROR */
}
  
/* I2C Write */
buf[0] = reg;
buf[1] = 0x43;
buf[2] = 0x65;
if (write(file, buf, 3) != 3) {
  /* ERROR HANDLING: i2c transaction failed */
}
  
/* I2C Read */
if (read(file, buf, 1) != 1) {
  /* ERROR */
}

Linux 格式

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struct i2c_rdwr_ioctl_data {  
        struct i2c_msg __user *msgs;    /* pointers to i2c_msgs */  
        __u32 nmsgs;                    /* number of i2c_msgs */  
};  

struct i2c_msg {
        __u16 addr;                     /* slave address                        */
        __u16 flags;
#define I2C_M_RD                0x0001  /* read data, from slave to master */
                                        /* I2C_M_RD is guaranteed to be 0x0001! */
#define I2C_M_TEN               0x0010  /* this is a ten bit chip address */
#define I2C_M_RECV_LEN          0x0400  /* length will be first received byte */
#define I2C_M_NO_RD_ACK         0x0800  /* if I2C_FUNC_PROTOCOL_MANGLING */
#define I2C_M_IGNORE_NAK        0x1000  /* if I2C_FUNC_PROTOCOL_MANGLING */
#define I2C_M_REV_DIR_ADDR      0x2000  /* if I2C_FUNC_PROTOCOL_MANGLING */
#define I2C_M_NOSTART           0x4000  /* if I2C_FUNC_NOSTART */
#define I2C_M_STOP              0x8000  /* if I2C_FUNC_PROTOCOL_MANGLING */
        __u16 len;              /* msg length                           */
        __u8 *buf;              /* pointer to msg data                  */
};

SMBUS

Spec

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# (Master/Slave:bit)
S(M:1) + Slave Address(M:7) + Wr(M:1) + A(S:1) + DATA(M:8) + A(S:1) + P(M:1)

每一個 Slave Device 都有獨一的 address，可以寫在 Slave Address 裡面

但 Slave Address 有一些預設的 address 不能用

2016-08-30_095751.png

Debug Level

參考-1

參考-2

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0 (KERN_EMERG)  The system is unusable.
1 (KERN_ALERT)  Actions that must be taken care of immediately.
2 (KERN_CRIT)   Critical conditions.
3 (KERN_ERR)    Noncritical error conditions.
4 (KERN_WARNING)Warning conditions that should be taken care of.
5 (KERN_NOTICE) Normal, but significant events.
6 (KERN_INFO)   Informational messages that require no action.
7 (KERN_DEBUG)  Kernel debugging messages, output by the kernel if the developer enabled debugging at compile time.


# 目前 Level 設定
cat /proc/sys/kernel/printk
7       4       1       7

# 設定 Level 
dmesg -n 7
echo "0 0 0 0" > /proc/sys/kernel/printk
echo "8" > /proc/sys/kernel/printk

# 顯示 message
tail /var/log/messages
dmesg

OpenSource

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CC=../XXX/arm-linux-
ROOT=../image

CPPFLAGS := -DMY_FALG
INCLUDE_PATH := ../include
TOOL_PATH := ./

i2cdetect: i2cdetect.c i2cbusses.c ../lib/smbus.c 
	$(CC)gcc -I$(INCLUDE_PATH) -I$(TOOL_PATH) $(CPPFLAGS)  -static -o  $@ $^
	cp ./i2cdetect $(ROOT)
	
i2cdump: i2cdump.c i2cbusses.c util.c ../lib/smbus.c 
	$(CC)gcc -I$(INCLUDE_PATH) -I$(TOOL_PATH) $(CPPFLAGS)  -static -o  $@ $^
	cp ./i2cdump $(ROOT)
	
i2cget: i2cget.c i2cbusses.c util.c ../lib/smbus.c 
	$(CC)gcc -I$(INCLUDE_PATH) -I$(TOOL_PATH) $(CPPFLAGS)  -static -o  $@ $^
	cp ./i2cget $(ROOT)
	
i2cset: i2cset.c i2cbusses.c util.c ../lib/smbus.c 
	$(CC)gcc -I$(INCLUDE_PATH) -I$(TOOL_PATH) $(CPPFLAGS)  -static -o  $@ $^
	cp ./i2cset $(ROOT)

I2C_Test: I2C_Test.c i2cbusses.c util.c ../lib/smbus.c 
	$(CC)gcc -I$(INCLUDE_PATH) -I$(TOOL_PATH) $(CPPFLAGS)  -static -o  $@ $^
	cp ./I2C_Test $(ROOT)	
	
	
TOOLS_TARGETS	:= i2cdetect i2cdump i2cget i2cset I2C_Test	
all: $(TOOLS_TARGETS)
	
clean:
	rm -rf *.o i2cdetect i2cdump i2cget i2cset

參考

參考-1

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參考-3