From 470f8a4d66d917d2d67b4c3963d804576f956523 Mon Sep 17 00:00:00 2001 From: patacongo Date: Fri, 2 Sep 2011 13:59:46 +0000 Subject: Add I2C README file git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3934 42af7a65-404d-4744-a932-0658087f49c3 --- apps/system/i2c/README.txt | 245 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 245 insertions(+) create mode 100755 apps/system/i2c/README.txt (limited to 'apps/system/i2c') diff --git a/apps/system/i2c/README.txt b/apps/system/i2c/README.txt new file mode 100755 index 000000000..cd8e44af8 --- /dev/null +++ b/apps/system/i2c/README.txt @@ -0,0 +1,245 @@ +README File for the I2C Tool +============================ + +The I2C tool provides a way to debug I2C related problems. This README file +will provide usage information for the I2C tools. + +CONTENTS +======== + + o Help + o Common Line Form + o Common Command Options + - "Sticky" Options + - Environment variables + - Common Option Summary + o Command summary + - bus + - dev + - get + - set + +HELP +==== + +First of all, the I2C tools supports a pretty extensive help output. That +help output can be view by entering either: + + nsh> i2c help + +or + + nsh> i2c ? + +Here is an example of the help output. I shows the general form of the +command line, the various I2C commands supported with their unique command +line options, and a more detailed summary of the command I2C command +options. + + nsh> i2c help + Usage: i2c [arguments] + Where is one of: + + Show help: ? + List buses: bus [OPTIONS] + List devices: dev [OPTIONS] + Read register: get [OPTIONS] + Show help: help + Write register: set [OPTIONS] + + Where common "sticky" OPTIONS include: + [-a addr] is the I2C device address (hex). Default: 03 Current: 03 + [-b bus] is the I2C bus number (decimal). Default: 1 Current: 1 + [-r regaddr] is the I2C device register address (hex). Default: 00 Current: 00 + [-w width] is the data width (8 or 16 decimal). Default: 8 Current: 8 + [-s|n], send/don't send start between command and data. Default: -n Current: -n + [-f freq] I2C frequency. Default: 400000 Current: 400000 + + NOTES: + o An environment variable like $PATH may be used for any argument. + o Arguments are "sticky". For example, once the I2C address is + specified, that address will be re-used until it is changed. + + WARNING: + o The I2C dev command may have bad side effects on your I2C devices. + Use only at your own risk. + +COMMAND LINE FORM +================= + +The I2C is started from NSH by invoking the 'i2c' command from the NSH +command line. The general form of the 'i2c' command is: + + i2c [arguments] + +Where is a "sub-command" and identifies one I2C operations supported +by the tool. [arguments] represents the list of arguments needed to perform +the I2C operation. Those arguments vary from command to command as +described below. However, there is also a core set of common OPTIONS +supported by all commands. So perhaps a better representation of the +general I2C command would be: + + i2c [OPTIONS] [arguments] + +Where [OPTIONS] represents the common options and and arguments represent +the operation-specific arguments. + +COMMON COMMAND OPTIONS +====================== + +"Sticky" Options +---------------- +In order to interact with I2C devices, there are a number of I2C parameters +that must be set correctly. One way to do this would be to provide to set +the value of each separate command for each I2C parameter. The I2C tool +takes a different approach, instead: The I2C configuration can be specified +as a (potentially long) sequence of command line arguments. + +These arguments, however, are "sticky." They are sticky in the sense that +once you set the I2C parameter, that value will remain until it is reset +with a new value (or until you reset the board). + +Environment Variables +--------------------- +NOTE also that if environment variables are not disabled (by +CONFIG_DISABLE_ENVIRON=y), then these options may also be environment +variables. Environment variables must be preceded with the special +character $. For example, PWD is the variable that holds the current +working directory and so $PWD could be used as a command line argument. The +use of environment variables on the I2C tools command is really only useful +if you wish to write NSH scripts to execute a longer, more complex series of +I2C commands. + +Common Option Summary +--------------------- + +[-a addr] is the I2C device address (hex). Default: 03 Current: 03 + + The [-a addr] sets the I2C device address. The valid range is 0x03 + through 0x77 (this valid range is controlled by the configuration settings + CONFIG_I2CTOOL_MINADDR and CONFIG_I2CTOOL_MAXADDR). If you are working + with the same device, the address needs to be set only once. + + All I2C address are 7-bit, hexadecimal values. + + Note that in the "help" output above also shows both default value of + the I2C address (03 hex) and the current address value (also 03). + +[-b bus] is the I2C bus number (decimal). Default: 1 Current: 1 + + Most devices support multiple I2C devices and also have unique bus + numbering. This option identifies which bus you are working with now. + The valid range of bus numbers is controlled by the configuration settings + CONFIG_I2CTOOL_MINBUS and CONFIG_I2CTOOL_MAXBUS. + + The bus numbers are small, decimal numbers. + +[-r regaddr] is the I2C device register address (hex). Default: 00 Current: 00 + + The I2C set and get commands will access registers on the I2C device. This + option selects the device register address (sometimes called the sub-address). + This is an 8-bit hexadecimal value. The maximum value is determined by + the configuration setting CONFIG_I2CTOOL_MAXREGADDR. + +[-w width] is the data width (8 or 16 decimal). Default: 8 Current: 8 + + Device register data may be 8-bit or 16-bit. This options selects one of + those two data widths. + +[-s|n], send/don't send start between command and data. Default: -n Current: -n + + This determines whether or not there should be a new I2C START between + sending of the register address and sending/receiving of the register data. + +[-f freq] I2C frequency. Default: 400000 Current: 400000 + + The [-f freq] sets the frequency of the I2C device. + +COMMAND SUMMARY +=============== + +We have already seen the I2C help (or ?) commands above. This section will +discussethe remaining commands. + +List buses: bus [OPTIONS] +-------------------------- + +This command will simply list all of the configured I2C buses and indicate +which are supported by the driver and which are not: + + BUS EXISTS? + Bus 1: YES + Bus 2: NO + +The valid range of bus numbers is controlled by the configuration settings +CONFIG_I2CTOOL_MINBUS and CONFIG_I2CTOOL_MAXBUS. + +List devices: dev [OPTIONS] +------------------------------------------ + +The 'dev' command will attempt to identify all of the I2C devices on the +selected bus. The and arguments are 7-bit, hexadecimal +I2C addresses. This command will examine a range of addresses beginning +with and continuing through . It will request the value +of register zero from each device. + +If the device at an address responds, then this command will display the +address of the device. If the device does not respond, this command will +display "--". The resulting display is like: + +nsh> i2c dev 03 77 + 0 1 2 3 4 5 6 7 8 9 a b c d e f +00: -- -- -- -- -- -- -- -- -- -- -- -- -- +10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- +20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- +30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- +40: -- -- -- -- -- -- -- -- -- 49 -- -- -- -- -- -- +50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- +70: -- -- -- -- -- -- -- -- + +WARNINGS: + o The I2C dev command may have bad side effects on certain I2C devices. + For example, if could cause data loss in an EEPROM device. + o The I2C dev command also depends upon the underlying behavior of the + I2C driver. How does the driver respond to addressing failures? + +Read register: get [OPTIONS] +---------------------------- + + This command will read the value of the I2C register using the selected + I2C parameters in the common options. No other arguments are required. + + This command with write the 8-bit address value then read an 8- or 16-bit + data value from the device. Optionally, it may re-start the transfer + before obtaining the data. + + On success, the output will look like the following (the data value + read will be shown as a 4-character hexadecimal number if the 16-bit + data width option is selected). + + READ Bus: 1 Addr: 49 Subaddr: 04 Value: 96 + + All values (except the bus numbers) are hexadecimal. + +Write register: set [OPTIONS] +------------------------------------- + + This command will write a value to an I2C register using the selected + I2C parameters in the common options. The value to write must be provided + as the final, hexadecimal value. This value may be an 8-bit value (in the + range 00-ff) or a 16-bit value (in the range 0000-ffff), depending upon + the selected data width. + + This command with write the 8-bit address value then write the 8- or 16-bit + data value to the device. Optionally, it may re-start the transfer + before writing the data. + + On success, the output will look like the following (the data value + written will be shown as a 4-character hexadecimal number if the 16-bit + data width option is selected). + + WROTE Bus: 1 Addr: 49 Subaddr: 04 Value: 96 + + All values (except the bus numbers) are hexadecimal. + + -- cgit v1.2.3