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SCMDCTL(1) General Commands Manual SCMDCTL(1)
NAME
scmdctl - Command line utility to interact with a Sparkfun Serial
Controlled Motor Driver
SYNOPSIS
scmdctl [-dhl] [-b baud rate] [-s SPI slave address] device identify
[module]
scmdctl [-dhl] [-b baud rate] [-s SPI slave address] device diagnostics
[module]
scmdctl [-dhl] [-b baud rate] [-s SPI slave address] device motor
get | set | invert | bridge | enable | disable
module ([get] | set | invert | bridge) A | B (set | invert)
value (set)
scmdctl [-dhl] [-b baud rate] [-s SPI slave address] device read_register
module register [register_end]
scmdctl [-dhl] [-b baud rate] [-s SPI slave address] device
write_register module register_value
scmdctl [-dhl] [-b baud rate] [-s SPI slave address] device restart
scmdctl [-dhl] [-b baud rate] [-s SPI slave address] device re-enumerate
scmdctl [-dhl] [-b baud rate] [-s SPI slave address] device update_rate
get | set | force rate (set)
scmdctl [-dhl] [-b baud rate] [-s SPI slave address] device expansion_bus
get | set 50kHz | 100kHz | 400kHz (set)
scmdctl [-dhl] [-b baud rate] [-s SPI slave address] device lock
get | lock | unlock
local_user | local_master | global_user | global_master
scmdctl [-dhl] [-b baud rate] [-s SPI slave address] device spi_read_one
DESCRIPTION
The scmdctl utility interacts with a Sparkfun Serial Controlled Motor
Driver (SCMD) and provides a set of convient commands for most of the
functions that the SCMD has.
The options are as follows:
-d debug mode
-h displays help
-l displays the register names and numbers
-b baud rate when interacting with a SCMD using a tty uart
-s SPI slave address when interacting with a SCMD using SPI userland mode
The SCMD device may be a uart tty(4), a spi(4), device or a scmd(4)
device. The latency is very different depending on which device is used:
+------------+----------------------------------+------------------------------------------------------------------+
|Device | Latency | Description |
+============+==================================+==================================================================+
|/dev/ttyXXX | High for local modules and | This uses the built in command line parser |
| | very high for remote modules | in the SCMD device and must parse the text input and output |
+------------+----------------------------------+------------------------------------------------------------------+
|/dev/spiX | Reasonable for local modules and | This uses userland SPI access and must deal with |
| | high for remote modules | the view port in userland for remote modules |
+------------+----------------------------------+------------------------------------------------------------------+
|/dev/scmdX | Low for local modules and | The kernel handles the view port access for |
| | reasonable for remote modes | remote modules and presents a linear register map of all modules |
+------------+----------------------------------+------------------------------------------------------------------+
In all cases the module argument is 0 to 16, with 0 being the master
module. In cases where the module argument is optional, it defaults to
0. Each SCMD module can have two motors, labeled A and B. If the module
is bridged then only actions on the A motor have any effect.
The commands are as follows:
identify [module]
Print identifying information about the module on a specific
device.
diagnostics [module]
Print the diagnostics registers for a module.
motor get|set|invert|bridge|enable|disable
module([get]|set|invert|bridge) A|B(set|invert) value(set)
Interact with the motors. The subcommand arguments are as
follows:
+-----------+------------------------+-----------------------------------------------------------+
|Subcommand | Arguments | Description |
+===========+========================+===========================================================+
|get | [module] | Gets details about the motors |
+-----------+------------------------+-----------------------------------------------------------+
|set | module | Set the power value for a motor |
| | A or B | |
| | value from -127 to 127 | |
+-----------+------------------------+-----------------------------------------------------------+
|invert | module | Inverts the power value for a motor |
| | A or B | |
+-----------+------------------------+-----------------------------------------------------------+
|bridge | module | Bridge motors A and B on a module together |
+-----------+------------------------+-----------------------------------------------------------+
|enable | | Enable the driver, apply the directed power to the motors |
+-----------+------------------------+-----------------------------------------------------------+
|disable | | Disable the driver, remove all power |
+-----------+------------------------+-----------------------------------------------------------+
read_register module register [register_end]
Read the registers from a module starting with register and
optionally ending with register_end. The values for register and
register_end are in the range from 0 to 126 in either decimal or
hex or they may be a named register.
write_register module register value
Write a value to a register on a module. The register values are
from 0 to 126 in either decimal or hex or may be a named register
name. The value that can be written to a register is 0 to 255
either in decimal or hex.
restart
Issue a restart directive to the SCMD.
re-enumerate
Issue a re-enumeration command to the SCMD. This will cause the
master module to search the expansion bus I2C chain for
additional modules.
update_rate get|set|force rate(set)
Set the update rate in which the master module updates the remote
modules. If rate is set to 0 then updates will only happen when
force is done.
expansion_bus get|set 50kHz|100kHz|400kHz(set)
Set the speed of the expandsion I2C bus.
lock get|lock|unlock local_user|local_master|global_user|global_master
View lock or unlock one of the locks on the SCMD device. Global
locks are sent to any attached SCMD device on the expansion bus,
and local locks apply only to the master module.
spi_read_one
This command is usable only in SPI userland mode and performs a
single receive in the hopes of unsticking the SCMD device.
EXAMPLES
scmdctl /dev/dtyU0 identify
Perform a identify command against the serial device /dev/dtyU0 and
return the results.
scmdctl /dev/spi0 motor get 0
Get the status of the motors on module 0 by accessing the SCMD device
using userland SPI.
scmdctl /dev/scmd0 motor set 1 B 127
scmdctl /dev/scmd0 motor invert 1 B
Set the power value of the B motor on module 1 to 127 and then invert the
power. Note that the values returned by a get against module 1 will
still show the positive value 127, but will indicate that the motor power
is inverted.
scmdctl /dev/scmd0 read_register 0 0x00 4
scmdctl /dev/scmd0 read_register 0 FID CONFIG_BITS
Read the first four registers on the master SCMD module using the kernel
scmd(4) device. Both of those two examples return the same information.
SEE ALSO
iic(4), spi(4), scmdi2c(4), scmdspi(4),
HISTORY
The scmdctl utility first appeared in NetBSD 10.0.
AUTHORS
The scmdctl utility was written by Brad Spencer <brad@anduin.eldar.org>.
BUGS
When accessing the SCMD devices using tty uart access, it is not really
possible to deal with line noise and there is no safety checks built into
the device to help with this. It is entirely possible that the
scmdctl(1) command can hang in this mode. It is also possible and likely
that the scmdctl(1) command will hang after a restart is performed in
this mode.
Performing a read in SPI mode, either in the kernel or in userland, is a
little odd with the SCMD device. There is a requirement that a dummy or
null read be performed and if this does not work as expected further
reads will not work. The spi_read_one command is an attempt to unstick a
stuck SCMD device.
If the SPI or I2C pins are not set up when the kernel device driver
attaches it will not be able to display information about the device, but
it will also not be able to ask the device how many modules exist and
will more or less assume that only the master node exists. If further
set up is required after the device attaches, a re-enumeration should be
performed before any actions are done to the motors.
No attempt has been made with scmdctl(1) to make the failsafe functions
of the SCMD device available in any convient manor.
NetBSD 10.99 December 1, 2021 NetBSD 10.99