LEDs (MX-4)

Overview⚓︎

On the MX-4 platform the LEDs are configured under /opt/hm/pic_attributes/LED. See pic_attributes for a complete list of attributes.

All LEDs except power can be controlled from within Linux (see Pre configured LED behavior).

WiFi LEDs⚓︎

The green WiFi LED (mx4-wifi) is set up to be lit on netdev. You can overwrite this by setting it to none or another trigger. Some platforms do not have the mx4-wifi-red and this led is free to be used as you like.

echo none > /sys/class/leds/mx4-wifi/trigger
# On
echo 1 >  /sys/class/leds/mx4-wifi/brightness
echo 1 >  /sys/class/leds/mx4-wifi-red/brightness
# Off
echo 0 >  /sys/class/leds/mx4-wifi/brightness
echo 0 >  /sys/class/leds/mx4-wifi-red/brightness

Script to set LEDs⚓︎

You can use the script /opt/hm/set_led_flash.sh.

root@mx4-t30-29009999:~# /opt/hm/set_led_flash.sh
Usage: /opt/hm/set_led_flash.sh <index> <color> <freq>

index = 2 - GSM LED
index = 3 - GPS LED
index = 4 - FUNC LED
index = 5 - BUZZER

color = 0 - led off
color = 1 - blink off/green
color = 2 - blink off/orange
color = 3 - blink green/orange

freq = 0 - no blink
freq = 1-255 - Flashing with frequency; freq * 100 milliseconds

Pre configured LED behavior⚓︎

PWR⚓︎

The power LED is is green or flashing green yellow/orange if charging an internal battery. Depending on the level of charge it will change speed between the flashing green ↔ yellow until it is lit green. If the unit does not have a battery it will continue to flash green ↔ yellow.

Solid green when running on supply voltage and battery charge state is above 60 %.
Flashing green/yellow 1 Hz: Battery charge status is 41-60 % and charging.
Flashing green/yellow 2 Hz: Battery charge status is 21-40 % and charging.
Flashing green/yellow 4 Hz: Battery charge status is 0-20 % and charging.
Solid yellow when running on battery and the battery is above 60 %
Flashing yellow/off 1 Hz: Battery charge status is 41-60 %.
Flashing yellow/off 2 Hz: Battery charge status is 21-40 %.
Flashing yellow/off 4 Hz: Battery charge status is 0-20 %.
Flashing green/off 1 Hz: The unit is in boot process

STANDBY STATE⚓︎

One-shot PWR LED green/off (on 30 ms) approximately every 20 seconds.

ERROR STATE⚓︎

All LEDs (except WiFi) flashing green/off 5 Hz: The unit is in an error state. Failing to boot operating system. This is the default state when the unit is powered on.

FIRMWARE UPGRADE⚓︎

A firmware upgrade can be followed by monitoring the LED behavior.

All LEDs (except WiFi) flashing green/off 1 Hz: The unit is loading/running an image ("hmupdate.img") from USB driver or /boot. DO NOT REMOVE POWER!
When hmupdate.img is finished the system will start up. This will be indicated by PWR LED Flashing green/off in 1 Hz.
First boot after hmupdate.img is run we also update the coprocessor firmware. This is indicated by the following sequence:
FUNC LED Solid green and other LEDs off. Entered coprocessor bootloader and will load an application to update coprocessor bootloader.
FUNC LED solid green, GPS solid green and other LEDs off. Bootloader application is loaded and will update coprocessor bootloader.
FUNC LED Solid green and other LEDs off. Entered coprocessor bootloader and will load the final application.
LED behavior returns to normal operation.

During the above steps the GSM LED will flash when we are sending data to the coprocessor for upgrade.

Done!

Set LEDs (the hard way)⚓︎

LED flashing is configured by writing 4 bytes to the corresponding led_-file in Linux.

The configuration of the 4 bytes:

MSB	Second MSB	Second LSB	LSB
Frequency	Spare	Flash config	Current LED

Frequency⚓︎

Frequency is configured according to:

0 - Flashing off
1-255 - Flashing with frequency; value * 100 milliseconds

If only no alternative frequency is configured the time for each state will be the same. If different times are wanted also use alternative frequency.

Alternative frequency⚓︎

0 - No alternative frequency.
1-255 - Flashing with frequency; value * 100 milliseconds

Flash config⚓︎

A bitmask configures which states that shall be included in the flashing sequence.

Bit 0 - LED is off.
Bit 1 - LED first state.
Bit 2 - LED second state.

Current LED⚓︎

Sets which LED shall be lit upon reception of the configuration value. If only this value is set the LED will not change state until a new configuration is received, or the MX-4 is restarted. This value can also be used to configure oneshot flashing.

Oneshot⚓︎

Oneshot flashing is configured by only configuring the wanted finishing state in the flash config. In current LED the wanted starting state is configured. In frequency the wanted time for the oneshot is configured.

Example of configuration⚓︎

Flashing pattern calculation⚓︎

Frequency Calculation:
Byte 3, frequency byte: 1 second / 100 milliseconds = 10.
Unused Byte:
Byte 2: Not used, set to 0.
Bits in Byte 1:
Bit 0 and bit 1 used: ( (1 << 1) | (1 << 0) = 3 ).

Resultant values⚓︎

Byte 3	Byte 2	Byte 1	Byte 0
10	0	3	0

Concatenating bytes⚓︎

Full Value Calculation:
- 10 << (8 * 3) | ((1 << 1) | (1 << 0)) | (8 * 1) = 167772171
Adjustment for Initial State:
- To start the flashing at state 0: ( 167772171 )
- To start the flashing at state 1: Add 1 to the value in Byte 0.

Flashing between State 1 and State 2⚓︎

State 1 lit for 2 seconds and state 2 lit for 500 milliseconds.

Frequency calculations:
- Byte 3, frequency byte for State 1: ( 500ms/ 100ms = 5 )
- Byte 2, frequency byte for State 2: ( 2 seconds /100ms = 20 )
- Byte 1, bits 1 and 2 used: ( (1 << 2) | (1 << 1) = 6 )
- Byte 0, initial state configured as State 2: Set to 2 in this case.

Resultant configuration⚓︎

Byte 3	Byte 2	Byte 1	Byte 0
5	20	6	2

Calculation⚓︎

5 << (8 * 3) | 20 << (8 * 2) | 6 << 8 | 2 = 85198338

One-shot flash configuration⚓︎

To configure a one-shot flash, an initial state and a finishing state are set with the time for the initial state configured in Byte 3.

The initial state is specified in Byte 0, and the finishing state is specified in Byte 1.

This means that in Byte 1, only one state needs to be defined, and that state will persist until a new value is sent to the LED.