scmdctl
—
Command line utility to interact with a Sparkfun Serial
Controlled Motor Driver
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 |
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.
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.
The scmdctl
utility first appeared in
NetBSD 10.0.
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.