Pololu Jrk G2 21v3, Jrk G2 Series, Jrk G2 18v19, Jrk G2 24v21, Jrk G2 24v13 User Manual

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Jrk G2 Motor Controller User’s

Guide

https://www.pololu.com/docs/0J73/all Page 1 of 199

1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.1. Supported operating systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

1.2. Comparison to the original Jrk controllers . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2. Contacting Pololu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3. Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.1. Installing Windows drivers and software . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.2. Installing Linux software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.3. Installing macOS software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4. Basic setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

4.1. Choosing the motor, power supply, and Jrk . . . . . . . . . . . . . . . . . . . . . . . . 19

4.2. Connecting the motor and power supply . . . . . . . . . . . . . . . . . . . . . . . . . 21

4.3. Configuring and testing the motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5. Setting up the feedback method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5.1. Setting up open-loop control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5.2. Setting up analog feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

5.3. Setting up frequency feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

6. Setting up the control method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

6.1. Setting up USB control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

6.2. Setting up serial control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

6.3. Setting up I²C control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

6.4. Setting up analog control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

6.5. Setting up RC control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

7. Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

7.1. LED feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

7.2. Graph window . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

7.3. Analog/RC input handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

7.4. Analog/frequency feedback handling . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

7.5. PID calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

7.6. Motor settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

7.7. Error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

7.8. Logic power output (5V) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

7.9. Upgrading firmware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

8. Pinout and components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

9. Setting reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

10. Variable reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

11. Command reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

12. Serial command encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

13. I²C command encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

14. USB command encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

15. Writing PC software to control the Jrk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

Page 2 of 199

15.1. Example code to run jrk2cmd in C . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

15.2. Example code to run jrk2cmd in Ruby . . . . . . . . . . . . . . . . . . . . . . . . . 179

15.3. Example code to run jrk2cmd in Python . . . . . . . . . . . . . . . . . . . . . . . . 180

15.4. Running jrk2cmd with Windows shortcuts . . . . . . . . . . . . . . . . . . . . . . . 182

15.5. Example serial code for Linux and macOS in C . . . . . . . . . . . . . . . . . . . . 184

15.6. Example serial code for Windows in C . . . . . . . . . . . . . . . . . . . . . . . . . 189

15.7. Example serial code in Python . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

15.8. Example I²C code for Linux in C . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

15.9. Example I²C code for Linux in Python . . . . . . . . . . . . . . . . . . . . . . . . . 197

Page 3 of 199

1. Overview

The second-generation Jrk G2 motor controllers are designed to enable easy closed-loop speed

control or position control (but not both!) of a single brushed DC motor. They feature integrated support

for analog voltage or tachometer (frequency) feedback and a variety of control interfaces–USB for

direct connection to a computer, TTL serial and I²C for use with a microcontroller, RC hobby servo

pulses for use in an RC system, and analog voltages for use with a potentiometer or analog joystick.

A free configuration utility simplifies initial setup of the device, provides access to a wide array of

configurable settings, and allows for in-system testing and monitoring of the controller via USB.

Side-by-side comparison of the different Jrk G2 USB Motor Controllers with Feedback.

The table below lists the members of the Jrk G2 family and shows the key differences among them.

Jrk G2

21v3

Minimum operating voltage:

Recommended max operating voltage:

Max nominal battery voltage:

Max continuous current (no additional cooling):

Dimensions: 1.0″ × 1.2″ 1.4″ × 1.2″ 1.7″ × 1.2″

1 The 5V logic voltage drops when powered from a supply below about 5.2 V. 2 Transient operation (< 500 ms) up to 40 V. 3 30 V absolute max. 4 40 V absolute max.

(1)

4.5 V

(2)

28 V

24 V 18 V 28 V 18 V 28 V

2.6 A 19 A 13 A 27 A 21 A

Jrk G2 18v19

6.5 V 6.5 V 6.5 V 6.5 V

(3)

24 V

Jrk G2 24v13

(4)

34 V

Jrk G2 18v27

(3)

24 V

Jrk G2 24v21

34 V

(4)

1. Overview Page 4 of 199

• Easy open-loop or closed-loop control of one brushed DC motor

• A variety of control interfaces:

◦ USB for direct connection to a computer

◦ TTL serial operating at 5 V for use with a microcontroller

◦ I²C for use with a microcontroller

◦ RC hobby servo pulses for use in an RC system

◦ Analog voltage for use with a potentiometer or analog joystick

• Feedback options:

◦ Analog voltage (0 V to 5 V), for making a closed-loop servo system

◦ Frequency, for closed-loop speed control using pulse counting (for higher-

frequency feedback) or pulse timing (for lower-frequency feedback)

◦ None, for open-loop speed control

◦ Note: the Jrk does not support using quadrature encoders for position control

• Ultrasonic 20 kHz PWM for quieter operation (can be configured to use 5 kHz instead)

• Simple configuration and calibration over USB with free configuration software utility (for

Windows, Linux, and macOS)

• Configurable parameters include:

◦ PID period and PID coefficients (feedback tuning parameters)

◦ Maximum current

◦ Maximum duty cycle

◦ Maximum acceleration and deceleration

◦ Error response

◦ Input calibration (learning) for analog and RC control

• Optional CRC error detection eliminates communication errors caused by noise or software

faults

• Reversed-power protection

• Field-upgradeable firmware

• Optional feedback potentiometer disconnect detection

Features and specifications

1. Overview Page 5 of 199

Jrk G2 21v3 USB Motor Controller with

Feedback, bottom view with dimensions.

Jrk G2 18v19 USB Motor Controller with

Feedback, bottom view with

dimensions.

Jrk G2 18v27 USB Motor Controller with

Feedback, bottom view with

dimensions.

Note: This guide only applies to the Jrk G2 motor controllers, which have black circuit

boards. If you have one of the first-generation Jrk 21v3 or Jrk 12v12 controllers, which

have green circuit boards, you can find their user’s guide here [https://www.pololu.com/docs/

0J38].

1.1. Supported operating systems

We support using the Jrk G2 and its configuration software on Windows 7, Windows 8, Windows 10,

Linux, and macOS 10.11 or later. The Jrk G2 software is not likely to work on Windows 10 IoT Core,

which is very different from the normal desktop versions of Windows. The software is open source

[https://github.com/pololu/pololu-jrk-g2-software], so it could be ported to more platforms.

1.2. Comparison to the original Jrk controllers

This section lists most of the things you should consider if you have an existing application using the

original Jrk 21v3 or Jrk 12v12 controllers and are considering upgrading to a Jrk G2.

1. Overview Page 6 of 199

• The Jrk G2 circuit boards have different dimensions, mounting hole locations, and pin

locations.

• On the Jrk G2, the RC pulse input should be connected to the pin named RC instead of RX.

• On the Jrk G2, analog control inputs should be connected to SDA/AN instead of RX.

• An analog control potentiometer should generally be powered from SCL and GND if you want

to detect disconnection (instead of AUX and GND).

• The Jrk G2 does not have a pin named FB: analog feedback signals should be connected

to the FBA pin and frequency/tachometer feedback signals should be connected to the FBT

pin.

• An analog feedback potentiometer should generally be powered from AUX and POT− (21v3,

18v19, and 24v13 only), or AUX and GND.

• Unlike the FB pin on the original jrks, the FBA pin does not have a pull-up resistor. If you need

one, you can add it externally or connect FBA to FBT to take advantage of the FBT pull-up

resistor.

• The Jrk G2 uses a USB Micro-B connector (the original Jrks used Mini-B).

• The Jrk G2 uses different configuration software from the original Jrk controllers. It is

open source [https://github.com/pololu/pololu-jrk-g2-software] and works on Windows, Linux, and

macOS. See Section 3 for installation instructions.

• The Jrk G2 serial protocol is generally a superset of the original Jrk serial protocol, so in many

Motor driver improvements

Compared to the original Jrk controllers, the discrete MOSFET H-bridges on the Jrk G2 18v19,

24v13, 18v27, and 24v21 support higher operating voltages and larger output currents. Additionally,

those Jrk G2 models have configurable hardware current limiting: when the motor current exceeds a

configurable threshold, the motor driver uses current chopping to actively limit it.

The Jrk G2 21v3 uses a TB9051FTG motor driver that features hardware current chopping with a fixed

threshold of approximately 6.5 A.

Physical connection changes

You will need to keep some things in mind when updating the physical connections of an existing

application:

Configuration and software changes

There are several changes to keep in mind when configuring the Jrk G2 or updating any software that

communicates with it:

1. Overview Page 7 of 199

cases, serial interface software running on a microcontroller or computer (using the Jrk’s RX

and TX lines or its virtual USB serial ports) will not need to be modified to work with the Jrk

G2.

• The Jrk G2 native USB interface uses different product IDs and supports a different set of

USB commands. However, the “Set target” and “Motor off” commands are unchanged.

• The “detect baud rate” feature was removed, so you will need to configure the baud rate of

your Jrk ahead of time using the Jrk G2 Configuration Utility if you are controlling it over serial

with a microcontroller.

• The default “Feedback mode” on the Jrk G2 is “None” instead of “Analog”.

• On the Jrk G2, the analog control input pin (SDA/AN) does not have its pull-up resistor

enabled by default, but there is an option to enable it in the “Pin configuration” tab of the Jrk

G2 configuration utility. (The original Jrk always enabled a pull-up on RX, which served as

the analog input.)

• The Jrk G2’s “Feedback deadzone” feature has been changed so that it applies to “Duty cycle

target” instead of “Duty cycle”, which makes it compatible with the new deceleration limits.

• The Jrk G2’s “Duty cycle” variable will move towards zero (either immediately or limited by the

configurable deceleration limit) when there is an error, so the Jrk G2 will respect acceleration

limits properly once the error is resolved.

• The 8-bit “Current” variable (which can be fetched with the serial command 0x8F) has units

of 256 mA on the Jrk G2. A new 16-bit current variable is available with higher resolution.

• Unlike the original Jrk controllers, the Jrk G2 does not reset the state of all of its error

flags when you click “Apply settings” in the configuration utility. Error flags will generally be

preserved.

• The current limiting and current regulation options have changed. See Section 7.6 for details.

• The Jrk G2 has configurable deceleration limiting. Additionally, you can choose which errors

respect the deceleration limits.

• The Jrk G2 has a new “Wraparound” option for analog feedback, which is useful for systems

that continuously rotate over a full circle.

• PID coefficients and many other settings can be adjusted on the fly over serial, I²C, or USB,

using the new “Set RAM settings” command.

New features

The Jrk G2 also supports a variety of new, optional features. These features were added in a

backward-compatible way and should not have an effect on your application unless you purposely use

them. Some of the most notable new features are:

1. Overview Page 8 of 199

• The new “Force duty cycle target” command lets you override the result of the PID algorithm.

• The new “Force duty cycle” command lets you override the result of the PID algorithm while

also ignoring acceleration and deceleration limits.

• New frequency feedback options allow closed-loop speed control using a much larger range

of tachometer frequencies.

• Measurements of the RC input, analog control input, analog feedback input, and the

tachometer input can all be enabled even if the Jrk’s main algorithm is not using them to

control the motor.

• The Jrk G2’s new I²C interface provides another option to connect a microcontroller to the

Jrk, and allows you to control multiple Jrks without using AND gates or level shifters.

• The Jrk G2 can measure the voltage of its VIN power supply and provide this reading over

serial, I²C, and USB.

1. Overview Page 9 of 199

2. Contacting Pololu

We would be delighted to hear from you about any of your projects and about your experience with

the Jrk G2 motor controllers. You can contact us [https://www.pololu.com/contact] directly or post on our

forum [https://forum.pololu.com/]. Tell us what we did well, what we could improve, what you would like

to see in the future, or anything else you would like to say!

2. Contacting Pololu Page 10 of 199

1. Download and install the Jrk G2 Software and Drivers for Windows [https://www.pololu.com/

file/0J1494/pololu-jrk-g2-1.4.0-win.msi] (10MB msi).

2. During the installation, Windows will ask you if you want to install drivers. Click “Install” to

proceed.

3. After the installation has completed, plug the Jrk into your computer via USB. Windows

should recognize the Jrk and load the drivers that you just installed.

4. Open your Start Menu and search for “Jrk G2”. Select the “Jrk G2 Configuration Utility”

shortcut (in the Pololu folder) to launch the software.

5. In the upper left corner of the window, where it says “Connected to:”, make sure that it shows

something like “18v19 #01234567”. This indicates the version and serial number of the Jrk

G2 that the software has connected to. If it says “Not connected”, see the troubleshooting

section below.

• The Jrk G2 Configuration Utility is a graphical user interface (GUI) for configuring the Jrk,

viewing its status, and controlling it manually. You can find the configuration utility in your

Start Menu by searching for it or looking in the Pololu folder.

• The Jrk G2 Command-line Utility (jrk2cmd) is a command-line utility that can do most of what

the GUI can do, and more. You can open a Command Prompt and type jrk2cmd with no

arguments to a see a summary of its options.

3. Getting started

3.1. Installing Windows drivers and software

To install the drivers and software for the Jrk G2 on a computer running Microsoft Windows, follow

these steps:

The Jrk’s native USB interface implements Microsoft OS 2.0 Descriptors, so it will work

on Windows 8.1 or later without needing any drivers. The Jrk’s USB serial ports will work

on Windows 10 or later without drivers.

This Jrk G2 software consists of two programs:

The source code for the software [https://github.com/pololu/pololu-jrk-g2-software] is available.

USB troubleshooting for Windows

If the Jrk G2 software cannot connect to your Jrk after you plug it into the computer via USB, the tips

here can help you troubleshoot the Jrk’s USB connection.

3. Getting started Page 11 of 199

If you are using the Jrk G2 configuration utility, try opening the “Connected to:” drop-down box to see

if there are any entries in the list. If there is an entry, try selecting it to connect to it.

Make sure you have a Jrk G2. The Jrk G2 software does not work with the older Jrk 21v3 or Jrk 12v12.

If you have one of those products, you should refer to its user’s guide instead of this user’s guide.

Make sure you are using software that supports the Jrk G2. The original Jrk Configuration Utility does

not work with the Jrk G2. The Jrk G2 controllers have new USB product IDs. Third-party software for

the older Jrk 21v3 and Jrk 12v12 controllers might need to be updated, depending on how the software

works. If you are a developer of such software, see Section 1.2.

If you have connected any electronic devices to your Jrk besides the USB cable, you should

disconnect them.

You should look at the LEDs of the Jrk. If the LEDs are off, then the Jrk is probably not receiving power

from the USB port. If the green LED is flashing very briefly once per second, then the Jrk is receiving

power from USB, but it is not receiving any data. These issues can be caused by using a broken USB

port, using a broken USB cable, or by using a USB charging cable that does not have data wires.

Using a different USB port and a different USB cable, both of which are known to work with other

devices, is a good thing to try. Also, if you are connecting the Jrk to your computer via a USB hub, try

connecting it directly.

If the Jrk’s green LED is on all the time or flashing slowly, but you can’t connect to it in the Jrk software,

then there might be something wrong with your computer. A good thing to try is to unplug the Jrk from

USB, reboot your computer, and then plug it in again.

If that does not help, you should go to your computer’s Device Manager and locate all the entries for

the Jrk. Be sure to look in these categories: “Other devices”, “Ports (COM & LPT)”, and “Universal

Serial Bus devices”.

If the driver for the Jrk’s native USB interface is working, you should see an entry in the “Universal

Serial Bus devices” category named something like “Pololu Jrk G2 18v19” (or the corresponding name

if you have a different version).

If the drivers for the Jrk’s USB serial ports are working, you should see two entries in the “Ports

(COM & LPT)” category named something like “Pololu Jrk G2 18v19 Command Port” and “Pololu

Jrk G2 18v19 TTL Port”. The serial ports might be named “USB Serial Device” instead if you are

using Windows 10 or later and you plugged the Jrk into your computer before installing our drivers

for it. The generic names in the Device Manager will not prevent you from using the ports, but we

recommend fixing the names by right-clicking on each “USB Serial Device” entry, selecting “Update

Driver Software…”, and then selecting “Search automatically for updated driver software”. Windows

should find the drivers you already installed, which contain the correct name for the port.

3. Getting started Page 12 of 199

1. Download the version for your system from this list:

◦ Jrk G2 Software for Linux (x86) [https://www.pololu.com/file/0J1500/pololu-jrk-

If any of the entries for the Jrk in the Device Manager has a yellow triangle displayed over its icon, you

should double-click on the entry to get information about the error that is happening.

If you do not see entries for the Jrk in the Device Manager, then you should open the “View” menu

and select “Devices by connection”. Then expand the entries until you find your computer’s USB

controllers, hubs, and devices. See if there are any entries in the USB area that disappear when you

unplug the Jrk. This might give you important information about what is going wrong.

Do not attempt to fix driver issues in your Device Manager using the “Add legacy hardware” option.

This is only for older devices that do not support Plug-and-Play, so it will not help. If you already tried

this option, we recommend unplugging the Jrk from USB and then removing any entries you see for

the Jrk by right-clicking on them and selecting “Uninstall”. Do not check the checkbox that says “Delete

the driver software for this device”.

Windows 10 Device Manager showing the Jrk G2.

3.2. Installing Linux software

To install the software for the Jrk G2 on a computer running Linux, follow these steps:

3. Getting started Page 13 of 199

g2-1.4.0-linux-x86.tar.xz] (9MB xz) — works on 32-bit and 64-bit systems

◦ Jrk G2 Software for Linux (Raspberry Pi) [https://www.pololu.com/file/0J1501/pololu-

jrk-g2-1.4.0-linux-rpi.tar.xz] (6MB xz) — works on the Raspberry Pi and might work on

other ARM Linux systems

2. In a terminal, use cd to navigate to the directory holding the downloaded file. For example,

run cd ~/Downloads if it was downloaded to the “Downloads” folder in your home directory.

3. Run tar -xvf pololu-jrk-g2-*.tar.xz to extract the software. If you downloaded multiple

versions of the software, you should use an exact file name instead of an asterisk.

4. Run sudo pololu-jrk-g2-*/install.sh to install the software. You will need to have sudo

privilege on your system and you might need to type your password at this point. Look at the

output of the script to see if any errors happened.

5. After the installation has completed, plug the Jrk into your computer via USB. If you already

connected the Jrk earlier, unplug it and plug it in again to make sure the newly-installed udev

rules are applied.

6. Run jrk2cmd --list to make sure the software can detect the Jrk. This command should

print the serial number and product name of the Jrk. If it prints nothing, see the “USB

troubleshooting for Linux” section below.

7. If you are using a graphical desktop environment, run jrk2gui to start the configuration

utility. In the upper left corner of the window, where it says “Connected to:”, make sure that it

shows something like “18v19 #01234567”. This indicates the version and serial number of the

Jrk G2 that the software has connected to. If it says “Not connected”, see the troubleshooting

section below.

• The Jrk G2 Configuration Utility (jrk2gui) is a graphical user interface (GUI) for configuring

the Jrk G2 and viewing its status. You can open a terminal and type jrk2gui to run it.

• The Jrk G2 Command-line Utility (jrk2cmd) is a command-line utility that can do most of what

the GUI can do, and more. You can open a terminal and type jrk2cmd with no arguments to

a see a summary of its options.

This Jrk G2 software consists of two programs:

The Jrk G2 software for Linux is statically linked; it does not depend on any shared libraries. The

source code for the software [https://github.com/pololu/pololu-jrk-g2-software] is available. The Jrk G2

does not require any driver installation on Linux.

Software installation troubleshooting for Linux

If you do not have sudo privilege or you do not remember your password, you can skip running

3. Getting started Page 14 of 199

install.sh and just run the programs directly from the directory you extracted them to. You should

also consider moving the software to a more permanent location and adding that location to your PATH

as described below.

If you get a “No such file or directory” error while running ./install.sh , it is possible that your

system is missing one of the directories that the install script assumes will be present. Please contact

[https://www.pololu.com/contact] us to let us know about your system so we can consider supporting it

better in the future.

If you get the error “command not found” when you try to run jrk2cmd or jrk2gui , then you should

run echo $PATH to see what directories are on your PATH, and then make sure one of those directories

contains the Jrk executables or symbolic links to them. The installer puts symbolic links in /usr/local/

bin , so if that directory is not on your PATH, you should run export PATH=$PATH:/usr/local/bin to

add it. Also, you might want to put that line in your ~/.profile file so the directory will be on your

PATH in future sessions.

If you get the error “cannot execute binary file: Exec format error” when you try to run jrk2cmd or

jrk2gui , then it is likely that you downloaded the wrong version of the software from the list above.

If all of the listed versions give you this error, you will probably need to compile the software from

source by following the instructions in BUILDING.md [https://github.com/pololu/pololu-jrk-g2-software/blob/

master/BUILDING.md] in the source code [https://github.com/pololu/pololu-jrk-g2-software]. Please contact

[https://www.pololu.com/contact] us to let us know about your system so we can consider supporting it

better in the future.

If the Jrk G2 Configuration Utility window is too big to fit on your screen properly, try setting the

JRK2GUI_FONT_SIZE environment variable to “6” before running the software. You can do this by

running the command JRK2GUI_FONT_SIZE=6 jrk2gui in your terminal. You can experiment with font

sizes other than 6 to see if they work for you. You could also add the line export JRK2GUI_FONT_SIZE=6

to your ~/.profile to make the change permanent.

USB troubleshooting for Linux

If the Jrk G2 software cannot connect to your Jrk after you plug it into the computer via USB, the tips

here can help you troubleshoot the Jrk’s USB connection.

If you are using the Jrk G2 Configuration Utility, try opening the “Connected to:” drop-down box to see

if there are any entries in the list. If there is an entry, try selecting it to connect to it.

Make sure you have a Jrk G2. The Jrk G2 software does not work with the older Jrk 21v3 or Jrk 12v12.

If you have one of those products, you should refer to its user’s guide instead of this user’s guide.

Make sure you are using software that supports the Jrk G2. The original Jrk Configuration Utility does

3. Getting started Page 15 of 199

1. Download the Jrk G2 Software for macOS [https://www.pololu.com/file/0J1502/pololu-jrk-

g2-1.4.0-macos.pkg] (8MB pkg).

2. Double-click on the downloaded file to run it, and follow the instructions.

3. After the installation has completed, plug the Jrk into your computer via USB.

4. In your Applications folder, look for “Pololu Jrk G2”. Double-click on “Pololu Jrk G2” to start

the configuration utility.

5. In the upper left corner of the window, where it says “Connected to:”, make sure that it shows

something like “18v19 #01234567”. This indicates the version and serial number of the Jrk

G2 that the software has connected to. If it says “Not connected”, see the troubleshooting

not work with the Jrk G2. The Jrk G2 controllers have new USB product IDs. Third-party software for

the older Jrk 21v3 and Jrk 12v12 controllers might need to be updated, depending on how the software

works. If you are a developer of such software, see Section 1.2.

If you have connected any electronic devices to your Jrk besides the USB cable, you should

disconnect them.

You should look at the LEDs of the Jrk. If the LEDs are off, then the Jrk is probably not receiving power

from the USB port. If the green LED is flashing very briefly once per second, then the Jrk is receiving

power from USB, but it is not receiving any data. These issues can be caused by using a broken USB

port, using a broken USB cable, or by using a USB charging cable that does not have data wires.

Using a different USB port and a different USB cable, both of which are known to work with other

devices, is a good thing to try. Also, if you are connecting the Jrk to your computer via a USB hub, try

connecting it directly.

If the Jrk’s green LED is on all the time or flashing slowly, but you can’t connect to it in the Jrk software,

then there might be something wrong with your computer. A good thing to try is to unplug the Jrk from

USB, reboot your computer, and then plug it in again.

If you get a “Permission denied” error when trying to connect to the Jrk, you should make sure to copy

the 99-pololu.rules file into /etc/udev/rules.d and then unplug the Jrk and plug it back in again.

The install script normally takes care of installing that file for you.

If that does not help, you should try running lsusb to list the USB devices recognized by your

computer. Look for the Pololu vendor ID, which is 1ffb. You should also try running dmesg right after

plugging in the Jrk to see if there are any messages about it.

3.3. Installing macOS software

To install the configuration software for the Jrk G2 on a computer running macOS, follow these steps:

3. Getting started Page 16 of 199

section below.

• The Jrk G2 Configuration Utility (jrk2gui) is a graphical user interface (GUI) for configuring the

Jrk G2 and viewing its status. You can run it by clicking on “Pololu Jrk G2” in the Applications

folder, or you can open a terminal and type jrk2gui to run it.

• The Jrk G2 Command-line Utility (jrk2cmd) is a command-line utility that can do most of what

the GUI can do, and more. You can open a terminal and type jrk2cmd with no arguments to

a see a summary of its options.

This Jrk G2 software consists of two programs:

The source code for the software [https://github.com/pololu/pololu-jrk-g2-software] is available. The Jrk

G2 does not require any driver installation on macOS.

Software installation troubleshooting for macOS

If you get the error “command not found” when you try to run jrk2cmd or jrk2gui , then you should try

starting a new Terminal window. The installer adds a file named 99-pololu-jrk2 in the /etc/paths.d

directory to make sure the software gets added to your PATH, but the change will not take effect until

you open a new Terminal window.

The Jrk G2 software will not work on versions of macOS prior to 10.11.

USB troubleshooting for macOS