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7.1. LED feedback

The Jrk G2 motor controller has three LEDs to indicate its status.

The green LED indicates the USB status of the device. When you connect the Jrk to a computer via a USB cable, the green LED will start blinking slowly. The blinking continues until the Jrk gets a particular message from the computer that indicates that the Jrk is recognized. After the Jrk gets that message, the green LED will be on, but it will flicker briefly when there is USB activity. During suspend mode (i.e. when the Jrk is only powered from USB and the computer has gone to sleep), the green LED will blink very briefly once per second.

The red LED turns on if and only if there is an error (other than the Awaiting Command error bit) stopping the motor. This LED is tied to the ERR pin. For more information about error handling, see Section 7.7.

The yellow LED indicates the status of the motor and also gives some information about what errors, if any, are happening:

  • If an error (other than the “Awaiting command” error bit) is stopping the motor, the yellow LED will be off.
  • If the Awaiting Command Error bit is set or the Jrk is in open-loop speed control mode and the duty cycle is zero, the yellow LED will blink slowly (once per second).
  • If the motor is on and has reached the desired state, the yellow LED will be on solid.
    • For analog and frequency feedback modes, this means that the target is within 20 of the scaled feedback.
    • For open-loop speed control mode, this means that the duty cycle equals the duty cycle target.
  • If the motor is on and has not reached its desired state, the yellow LED will flash quickly (16 times per second).

The information expressed by the Jrk’s LEDs can also be seen by connecting the Jrk to a computer via USB, running the Jrk G2 Configuration Utility, and looking in the Status and Errors tabs.

Startup blinking

When the Jrk starts running, it tries to detect if it was reset by some special condition. If it experiences a brown-out reset, watchdog timer reset, software reset, stack overflow, or stack underflow, the Jrk will blink its yellow LED eight times over a one second period while the red LED is on at startup. While it is doing this blinking, the Jrk will not accept any commands, read any inputs, or run the motor. You can see the cause of the last reset in the Jrk G2 Configuration Utility software’s “Last reset” field.

Bootloader mode

In bootloader mode, which is used for updating the firmware of the Jrk and should only rarely be needed, the LEDs behave differently. The green LED still indicates the USB status, but it is different: after the bootloader gets a particular message from the computer that indicates that the bootloader is recognized, the green LED will start doing a double blinking pattern every 1.4 seconds. The yellow LED will usually be on solid, but it will blink quickly whenever a USB command is received. The red LED will be on if and only if there is no firmware currently loaded on the device.

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