227 lines
7.4 KiB
Plaintext
227 lines
7.4 KiB
Plaintext
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README File for the SPI Tool
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============================
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The I2C tool provides a way to debug SPI related problems. This README file
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will provide usage information for the SPI tools.
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CONTENTS
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========
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o System Requirements
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- SPI Driver
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- Configuration Options
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o Help
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o Common Line Form
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o Common Command Options
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- "Sticky" Options
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- Environment variables
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- Common Option Summary
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o Command summary
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- bus
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- dev
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- get
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- set
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- verf
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o I2C Build Configuration
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- NuttX Configuration Requirements
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- I2C Tool Configuration Options
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System Requirements
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===================
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The SPI tool is designed to be implemented as a NuttShell (NSH) add-on. Read
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the apps/nshlib/README.txt file for information about add-ons.
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Configuration Options
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---------------------
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CONFIG_NSH_BUILTIN_APPS - Build the tools as an NSH built-in command
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CONFIG_SPITOOL_MINBUS - Smallest bus index supported by the hardware (default 0).
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CONFIG_SPITOOL_MAXBUS - Largest bus index supported by the hardware (default 3)
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CONFIG_SPITOOL_DEFFREQ - Default frequency (default: 40000000)
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CONFIG_SPITOOL_DEFMODE - Default mode, where;
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0 = CPOL=0, CHPHA=0
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1 = CPOL=0, CHPHA=1
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2 = CPOL=1, CHPHA=0
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3 = CPOL=1, CHPHA=1
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CONFIG_SPITOOL_DEFWIDTH - Default bit width (default 8)
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CONFIG_SPITOOL_DEFWORDS - Default number of words to exchange (default 1)
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HELP
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====
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he SPI tools supports some help output. That help output can be view
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by entering either:
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nsh> spi help
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or
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nsh> spi ?
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Here is an example of the help output. I shows the general form of the
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command line, the various SPI commands supported with their unique command
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line options, and a more detailed summary of the command SPI command
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options.
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nsh> Usage: spi <cmd> [arguments]
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Where <cmd> is one of:
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Show help : ?
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List busses : bus
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SPI Exchange : exch [OPTIONS] [<hex senddata>]
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Show help : help
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Where common "sticky" OPTIONS include:
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[-b bus] is the SPI bus number (decimal). Default: 0 Current: 2
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[-f freq] SPI frequency. Default: 4000000 Current: 4000000
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[-m mode] Mode for transfer. Default: 0 Current: 0
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[-u udelay] Delay after transfer in uS. Default: 0 Current: 0
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[-w width] Width of bus. Default: 8 Current: 8
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[-x count] Words to exchange Default: 1 Current: 4
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NOTES:
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o An environment variable like $PATH may be used for any argument.
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o Arguments are "sticky". For example, once the SPI address is
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specified, that address will be re-used until it is changed.
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WARNING:
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o The SPI commands may have bad side effects on your SPI devices.
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Use only at your own risk.
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COMMAND LINE FORM
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=================
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The SPI is started from NSH by invoking the 'spi' command from the NSH
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command line. The general form of the 'spi' command is:
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spi <cmd> [arguments]
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Where <cmd> is a "sub-command" and identifies one SPI operation supported
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by the tool. [arguments] represents the list of arguments needed to perform
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the SPI operation. Those arguments vary from command to command as
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described below. However, there is also a core set of common OPTIONS
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supported by all commands. So perhaps a better representation of the
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general SPI command would be:
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i2c <cmd> [OPTIONS] [arguments]
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Where [OPTIONS] represents the common options and and arguments represent
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the operation-specific arguments.
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COMMON COMMAND OPTIONS
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======================
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"Sticky" Options
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----------------
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In order to interact with SPI devices, there are a number of SPI parameters
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that must be set correctly. One way to do this would be to provide to set
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the value of each separate command for each SPI parameter. The SPI tool
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takes a different approach, instead: The SPI configuration can be specified
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as a (potentially long) sequence of command line arguments.
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These arguments, however, are "sticky." They are sticky in the sense that
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once you set the SPI parameter, that value will remain until it is reset
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with a new value (or until you reset the board).
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Environment Variables
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---------------------
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NOTE also that if environment variables are not disabled (by
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CONFIG_DISABLE_ENVIRON=y), then these options may also be environment
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variables. Environment variables must be preceded with the special
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character $. For example, PWD is the variable that holds the current
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working directory and so $PWD could be used as a command line argument. The
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use of environment variables on the I2C tools command is really only useful
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if you wish to write NSH scripts to execute a longer, more complex series of
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SPI commands.
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Common Option Summary
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---------------------
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[-b bus] is the SPI bus number (decimal). Default: 0
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Which SPI bus to commiuncate on. The bus must have been initialised
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as a character device in the config in the form /dev/spiX (e.g. /dev/spi2).
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The valid range of bus numbers is controlled by the configuration settings
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CONFIG_SPITOOL_MINBUS and CONFIG_SPITOOL_MAXBUS.
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The bus numbers are small, decimal numbers.
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[-m mode] SPI Mode for transfer.
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Which of the available SPI modes is to be used. Options are;
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0 = CPOL=0, CHPHA=0
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1 = CPOL=0, CHPHA=1
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2 = CPOL=1, CHPHA=0
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3 = CPOL=1, CHPHA=1
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[-u udelay] Delay after transfer in uS. Default: 0
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Any extra delay to be provided after the transfer. Not normally needed
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from the command line.
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[-x count] Words to exchange Default: 1
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The number of words to be transited over the bus. For sanitys sake this is
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limited to a relatively small number (40 by default). Any data on the
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command line is sent first, padded by 0xFF's while any remaining data
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are received.
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[-w width] is the data width (varies according to target). Default: 8
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Various SPI devices support different data widths. This option is untested.
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[-f freq] I2C frequency. Default: 4000000 Current: 4000000
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The [-f freq] sets the frequency of the SPI device. The default is very conservative.
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COMMAND SUMMARY
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===============
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List buses: bus [OPTIONS]
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--------------------------
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This command will simply list all of the configured SPI buses and indicate
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which are supported by the driver and which are not:
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BUS EXISTS?
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Bus 1: YES
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Bus 2: NO
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The valid range of bus numbers is controlled by the configuration settings
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CONFIG_SPITOOL_MINBUS and CONFIG_SPITOOL_MAXBUS.
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Exchange data: exch [OPTIONS] <Optional TX Data>
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------------------------------------------------
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This command triggers an SPI transfer, returning the data back from the far end.
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As an example (with MOSI looped back to MISO);
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nsh>spi exch -b 2 -x 4 aabbccdd
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Received: AA BB CC DD
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nsh>
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Note that the TXData are always specified in hex, and are always two digits each,
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case insensitive.
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I2C BUILD CONFIGURATION
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=======================
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NuttX Configuration Requirements
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--------------------------------
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The SPI tools requires the following in your NuttX configuration:
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1. Application configuration.
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Using 'make menuconfig', select the SPI tool. The following
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definition should appear in your .config file:
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CONFIG_SYSTEM_SPI=y
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2. Device-specific SPI driver support must be enabled:
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CONFIG_SPI_DRIVER=y
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The SPI tool will then use the SPI character driver to access the SPI
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bus. These devices will reside at /dev/spiN where N is the I2C bus
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number.
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NOTE 1: The SPI driver ioctl interface is defined in
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include/nuttx/spi/spi.h.
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