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linux driver for an i2c device -- two byte read

开发者 https://www.devze.com 2023-03-06 18:35 出处:网络
I\'m trying to write a Linux driver for an I2C device that seems to be slightly different from a typical device. Specifically, I need to read t开发者_JAVA百科wo bytes in a row without sending a stop b

I'm trying to write a Linux driver for an I2C device that seems to be slightly different from a typical device. Specifically, I need to read t开发者_JAVA百科wo bytes in a row without sending a stop bit in between, like so:

[S] [Slave Addr | 0] [A] [Reg Addr 1] [A] [Sr] [Slave Addr | 1] [Data Byte 1] [NA]  
[Sr][Slave Addr | 0] [A] [Reg Addr 2] [A] [Sr] [Slave Addr | 1] [Data Byte 2] [NA] [P]

I've looked at a few ways of doing this, including i2c_transfer(), i2c_master_send() and i2c_master_recv(), but I'm not sure if they will support these. Is there any way of doing this directly with these functions that isn't horribly painful? The documentation that I've found so far hasn't been entirely clear on the matter.

EDIT#1: adding symbols key to make it readable. Courtesy to http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/i2c/i2c-protocol

 Key to symbols
==============

S     (1 bit) : Start bit
P     (1 bit) : Stop bit
Rd/Wr (1 bit) : Read/Write bit. Rd equals 1, Wr equals 0.
A, NA (1 bit) : Accept and reverse accept bit. 
Addr  (7 bits): I2C 7 bit address. Note that this can be expanded as usual to 
                get a 10 bit I2C address.
Comm  (8 bits): Command byte, a data byte which often selects a register on
                the device.
Data  (8 bits): A plain data byte. Sometimes, I write DataLow, DataHigh
            for 16 bit data.
Count (8 bits): A data byte containing the length of a block operation.
[..]: Data sent by I2C device, as opposed to data sent by the host adapter.


no stop bit is send between bytes in the same read/write operation. i2c_master_recv is probably what you need.

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