H. daisy-chaining, Using a pc and a jrk together as the master device, Using a jrk as a slave device – Pololu Jrk USB User Manual
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different from the duty cycle target because it takes in to account all of the jrk’s configurable limits: maximum
acceleration, maximum duty cycle, maximum current, and also brake duration (
).
• PID period count: This is the number of PID periods that have elapsed. It resets to 0 after reaching 65535.
The duration of the PID period can be configured (
Note: All command bytes from 0x81 to 0xBF that are not listed in this section or
are
undocumented variable reading commands that will result in a serial response from the jrk and not
generate a serial protocol error. These commands are not useful, but they are not harmful.
4.h. Daisy-Chaining
This section is a guide to integrating the jrk in to a project that has multiple TTL serial devices that use the Pololu
Protocol or some compatible protocol. This section contains no new information about the jrk: all of the information
in this section can be deduced from the definitions of the three serial modes (
) and the Pololu Protocol
).
First of all, assign each device in the project a different device number so that they can be individually addressed
by Pololu Protocol serial commands. For the jrk, this can be done in the Input tab of the configuration utility.
The following diagram shows how to connect one master and many slave devices together into a chain. Each
of the devices may be a jrk or any other device compatible with the Pololu Protocol, such as a
,
,
or
a
microcontroller.
Daisy chaining serial devices using the Pololu
protocol. An optional AND gate is used to join
multiple TX lines.
Using a PC and a jrk together as the master device
The jrk can enable a personal computer to be the master device. The jrk must be connected to a PC with a USB cable
and configured to be in either USB Dual Port or USB Chained serial mode. Serial input mode must be used to
receive responses from slave devices (if you do not need to receive reponses, you may use other input modes). In USB
Dual Port mode, the Command Port on the PC is used for sending commands directly to the jrk, and the TTL Port on
the PC is used to send commands to all of the slave devices. In the USB Chained mode, only the Command Port is
used on the PC, to communicate with the jrk and all of the slave devices. Select the mode that is most convenient for
your application or easiest to implement in your programming language.
Using a jrk as a slave device
The jrk can act as a slave device when configured to be in the UART serial mode and Serial input mode. In this
mode, commands are received on the RX line, and responses are sent on the TX line. A USB connection to a PC is
not required, though an RX-only Comand Port is available on the PC for debugging or other purposes.
Pololu Jrk USB Motor Controller User's Guide
© 2001–2014 Pololu Corporation
4. Using the Serial Interface
Page 37 of 45