3.e. Indicator LEDs

LED Overview

The qik has two LEDs that are used to provide feedback about its state of operation:

  • Status LED (green): This green LED provides a heartbeat to let you know that your qik is alive and what state the qik is in, and it also acts as a serial activity indicator.
  • Error LED (red): This red LED is tied to the ERR output pin and lights when the ERR pin drives high in response to an error. Once an error occurs, the LED remains lit until a serial command is issued to read the error byte, at which point the LED turns off. For more information on the possible error conditions, please see Section 5.b.

Automatic Baud Detection Phase

When the qik first starts up in automatic baud detection mode, it enters a phase in which it is waiting to receive the byte 0xAA (170 in decimal) at a baud rate that is within the range of 1200 bps to 38,400 bps. If the serial receive line, RX, is pulled high, as is expected for an idle TTL serial line and the default state of an unconnected RX, the green status LED flashes on and off evenly every 0.4 s. If the serial receive line is held low, this is indicative of a bad serial connection and the red error flashes on and off evenly every 0.4 s (with the green status LED off). Once the baud is detected, this phase ends and the qik proceeds to normal operation.

Firmware version 2 only: If a serial byte other than 0xAA is received in this mode, or if 0xAA is transmitted at an invalid baud rate, the red error LED turns on and stays on until the automatic baud detection phase ends. This gives you feedback that the baud has not yet successfully been set and the controller is still in the automatic detection phase. Firmware version 1 flashes the red LED very briefly if a serial byte other than 0xAA is received in this mode, which can make it difficult to tell that the qik detected any serial activity.

Normal Operation

In normal operation, the green status LED very briefly flashes a heartbeat every two seconds. If any serial activity is detected, the green LED turns on until the next heartbeat turns it off. If a serial error occurs, the red LED turns on and remains on until you issue a get-error command (see Section 5.b).

Demo Mode

In demo mode, the LEDs will cycle through the pattern:

  1. red and green ON
  2. red ON and green OFF
  3. red OFF and green ON
  4. red and green OFF

This cycle takes several seconds, and each of the four LED states corresponds to a different output state of the qik’s motor ports. When the red error LED is on, motor M0 is active, and when the red error LED is off, motor M1 is active. When the green status LED is on, the active motor is moving forward, and when the green status LED is off, the active motor is moving in reverse.

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Pololu Qik 2s9v1 Dual Serial Motor Controller
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