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SysCon Microcontroller Options

The SysCon microcontroller inside the Tachyon device manages the power state and enables advanced features to control boot behavior and debugging access. This section covers three configurable options:

  • AutoBoot
  • WakePinEnable
  • FastBootEnabled

AutoBoot​

The AutoBoot setting determines whether the device should automatically power on after a cold start.

Behavior:​

  • Default: false
  • When true:
    • If the device receives power (e.g., battery, 5V or USB) and the device is off, the device will automatically boot without requiring the power button.
    • This power-on occurs 2 seconds after power is applied, allowing time for system stabilization.
    • If the device was previously shut down explicitly via software, it will remain off until the button is pressed manually.
    • If the microcontroller reboots, it will assess the system state:
      • If the device was just cold-started, it will power on (subject to AutoBoot).
      • If the device was deliberately shut down, it will remain off.

Practical Note:​

When using both battery and USB/5V input:

  • Always connect the battery first, followed by USB/5V.
  • This ensures that the AutoBoot sequence is handled correctly on power-up.

πŸ”§ If you require a large debounce on the auto start, please contact us. This is not currently coded but can be added if needed.

WakePinEnable​

The WakePinEnable setting allows an external GPIO to trigger device power-on through a low-to-high transition.

Behavior:​

  • The wake pin is a CMOS-compatible input (0–3.3V logic).
  • When the pin goes high, the device powers on.
  • A low level does not shut down the device; it simply allows the trigger to be re-armed.
  • Transitions matter:
    • Low β†’ High = Power On
    • High β†’ Low = No effect
  • The wake pin can wake the device even if it was powered off via the button.
  • Button presses can override the wake pin state at any time.

πŸ”§ If you require an inverted logic (e.g., high = off), please contact us. This is not currently supported but can be added if needed.

FastBootEnabled​

When FastBootEnabled is set, the power button supports entering fastboot mode via extended press.

Behavior:​

  • Fastboot mode allows access to the bootloader over USB, enabling firmware updates or partition flashing.
  • When enabled:
    • Hold the button for 8 seconds on power-up (vs 3 seconds for EDL mode).
    • After 8 seconds, the device enters fastboot and the LED flashes purple.
    • You can now use the fastboot protocol over USB to communicate with the board.

Usage:​

This mode is primarily for development and factory flashing workflows and is inactive unless FastBootEnabled is set.

Reading and Writing Configuration Options​

You can use the helper script at /usr/bin/particle-tachyon-syscon.sh to inspect and modify SysCon configuration options. These options persist across reboots and influence device power behavior.

πŸ” Listing All Current Configurations​

sudo /usr/bin/particle-tachyon-syscon.sh list_config

This displays the current runtime values active inside the microcontroller.

βΈ»

πŸ“– Reading a Specific Option

sudo /usr/bin/particle-tachyon-syscon.sh get_config sys.auto_boot

Replace sys.auto_boot with any of the following supported keys:

  • sys.auto_boot
  • sys.wake_pin_enable
  • sys.fastboot_enabled

βΈ»

✏️ Setting an Option

sudo /usr/bin/particle-tachyon-syscon.sh set_config sys.auto_boot:true
  • Format: set_config key:value
  • Acceptable values: true or false

⚠️ Changing a setting is picked up automatically, but it might require a power cycle to take effect.

βΈ»

πŸ’‘ Example: Enable Wake Pin

sudo /usr/bin/particle-tachyon-syscon.sh set_config sys.wake_pin_enable:true