This is the syntax of i2c md command.
i2c md chip address[.0, .1, .2] [# of objects] - read from I2C device
I understood that chip will be replaced by address of the I2C device and address is replaced by the register address to be read
I want to understand what is the significance of [.0, .1, .2] in the above syntax
And please confirm [# of objects] is for length of bytes to be read.
Reading multiple bytes using I2C in U-Boot
In the above question, he explains that .2 is for 2 byte address , is it 10-bit address, and if so, .1 is for 7-bit address. What is .0 for..
If you issue i2c in u-boot, it gives you the usage of the command:
i2c md chip address[.0, .1, .2] [# of objects] - read from I2C device
Detailed explanation is given in cmd_i2c.c in u-boot sources, folder u-boot/common :
"/*
* I2C Functions similar to the standard memory functions.
*
* There are several parameters in many of the commands that bear further
* explanations:
*
* {i2c_chip} is the I2C chip address (the first byte sent on the bus).
* Each I2C chip on the bus has a unique address. On the I2C data bus,
* the address is the upper seven bits and the LSB is the "read/write"
* bit. Note that the {i2c_chip} address specified on the command
* line is not shifted up: e.g. a typical EEPROM memory chip may have
* an I2C address of 0x50, but the data put on the bus will be 0xA0
* for write and 0xA1 for read. This "non shifted" address notation
* matches at least half of the data sheets :-/.
*
* {addr} is the address (or offset) within the chip. Small memory
* chips have 8 bit addresses. Large memory chips have 16 bit
* addresses. Other memory chips have 9, 10, or 11 bit addresses.
* Many non-memory chips have multiple registers and {addr} is used
* as the register index. Some non-memory chips have only one register
* and therefore don't need any {addr} parameter.
*
* The default {addr} parameter is one byte (.1) which works well for
* memories and registers with 8 bits of address space.
*
* You can specify the length of the {addr} field with the optional .0,
* .1, or .2 modifier (similar to the .b, .w, .l modifier). If you are
* manipulating a single register device which doesn't use an address
* field, use "0.0" for the address and the ".0" length field will
* suppress the address in the I2C data stream. This also works for
* successive reads using the I2C auto-incrementing memory pointer.
*
* If you are manipulating a large memory with 2-byte addresses, use
* the .2 address modifier, e.g. 210.2 addresses location 528 (decimal).
*
* Then there are the unfortunate memory chips that spill the most
* significant 1, 2, or 3 bits of address into the chip address byte.
* This effectively makes one chip (logically) look like 2, 4, or
* 8 chips. This is handled (awkwardly) by #defining
* CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW and using the .1 modifier on the
* {addr} field (since .1 is the default, it doesn't actually have to
* be specified). Examples: given a memory chip at I2C chip address
* 0x50, the following would happen...
* i2c md 50 0 10 display 16 bytes starting at 0x000
* On the bus: <S> A0 00 <E> <S> A1 <rd> ... <rd>
* i2c md 50 100 10 display 16 bytes starting at 0x100
* On the bus: <S> A2 00 <E> <S> A3 <rd> ... <rd>
* i2c md 50 210 10 display 16 bytes starting at 0x210
* On the bus: <S> A4 10 <E> <S> A5 <rd> ... <rd>
* This is awfully ugly. It would be nice if someone would think up
* a better way of handling this.
*
* Adapted from cmd_mem.c which is copyright Wolfgang Denk ([email protected]).
*/"
For your example:
i2c md 0x50 0.2 0x10
0x50 - address of the slave
0.2 - memory display starts at address 0x000 (indicated by 0), the .2 specifies the length of the address field.
0x10 - shows that the i2c md command will display 16 registers.
So the command i2c md 0x50 0.2 0x10 states: Display 16 registers starting at address 0x000 (addr length is 2-bytes) from slave located at 0x50