.. _ecu_recovery:

ECU Recovery
=====================================================
.. contents:: Table of Contents
    :depth: 2

System Modes
------------

The ECU can run in one of two modes: **reprogramming mode** and **application
mode**. In reprogramming mode, the ECU can be reprogrammed using a CAN
Calibration Protocol (CCP) tool. In application mode, the ECU runs the loaded
software.

What is FEPS?
-------------

The Flash and EEPROM Programming Signal (FEPS) signals the OpenECU firmware to
enter reprogramming mode during startup. It is activated by applying voltage
to the FEPS pin on the ECU. Refer to the `Technical Specification tech-spec`
for pin details and supported FEPS modes.

Positive FEPS Mode
------------------

Positive FEPS mode starts when the voltage on the FEPS pin exceeds the
positive FEPS threshold. It attempts to use the CAN Calibration Protocol
(CCP) settings specified in the pre-loaded application.

**Reprogramming with positive FEPS using two power supplies:**

  1. Connect ECU power, ground, and ignition to one supply and set its voltage
     within the ECU's operating range. Turn off the supply.

  2. Connect the FEPS wire to another power supply set to a voltage greater
     than the positive FEPS threshold. Turn this supply on.

  3. Turn on the supply powering the ECU. Verify the module is in positive
     FEPS mode using :ref:`Flash Code Output <flash_code_output>`.

  4. Reprogram the ECU using the current CCP settings.

.. image:: ecu_recovery_img1.jpg
   :alt: Positive FEPS with two supplies for M220 ECU

Negative FEPS Mode
------------------

Negative FEPS mode starts when the FEPS pin voltage is below the negative FEPS
threshold. This mode uses default CAN Calibration Protocol (CCP) settings.

.. list-table::
   :header-rows: 1

   * - CCP setting
     - Default value
   * - CRO message identifier
     - 1785
   * - DTO message identifier
     - 1784
   * - Station address
     - 0
   * - CAN bus identifier
     - CAN 0
   * - CAN bus baud-rate
     - 250kBps or 500kBps

.. note::
   Refer to the User Guide to determine the default CAN baud-rate.

**Reprogramming with negative FEPS using batteries:**

.. image:: ecu_recovery_img2.jpg
   :alt: Negative FEPS using batteries for M220 ECU