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 convenient 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 are 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 convenient manner.

December 1, 2021 | NetBSD 11.0