Modifications

{{Pololu-Romi-32U4-NAV}}

{{Pololu-Romi-32U4-NAV}}

# Introduction

== Introduction ==

Our 32U4 family of boards come with a USB bootloader that can be used in conjunction with the Arduino IDE or AVRDUDE to load new programs onto the device. This section documents some technical details of the bootloader for advanced users who want to better understand how it works. If you just want to get started using your device, it is fine to skip this section.

Our 32U4 family of boards come with a USB bootloader that can be used in conjunction with the Arduino IDE or AVRDUDE to load new programs onto the device. This section documents some technical details of the bootloader for advanced users who want to better understand how it works. If you just want to get started using your device, it is fine to skip this section.

The A-Star 32U4 Bootloader is based on the [https://github.com/arduino/Arduino/tree/master/hardware/arduino/avr/bootloaders/caterina Caterina bootloader], which is the bootloader used on the [https://www.pololu.com/product/2192 Arduino Leonardo], [https://www.pololu.com/product/2188 Arduino Micro] and several other ATmega32U4 boards. The bootloader is open source and its [https://github.com/pololu/a-star/tree/master/bootloaders/caterina source code is available on GitHub]. The bootloader occupies the upper four kilobytes of the ATmega32U4’s program memory, leaving 28 KB for the user program. The bootloader’s USB interface consists of a single virtual serial port that accepts the programming commands defined in [http://www.atmel.com/images/doc1644.pdf AVR109]. The bootloader always runs first immediately after the AVR is reset.

The A-Star 32U4 Bootloader is based on the [https://github.com/arduino/Arduino/tree/master/hardware/arduino/avr/bootloaders/caterina Caterina bootloader], which is the bootloader used on the [https://www.pololu.com/product/2192 Arduino Leonardo], [https://www.pololu.com/product/2188 Arduino Micro] and several other ATmega32U4 boards. The bootloader is open source and its [https://github.com/pololu/a-star/tree/master/bootloaders/caterina source code is available on GitHub]. The bootloader occupies the upper four kilobytes of the ATmega32U4’s program memory, leaving 28 KB for the user program. The bootloader’s USB interface consists of a single virtual serial port that accepts the programming commands defined in [http://www.atmel.com/images/doc1644.pdf AVR109]. The bootloader always runs first immediately after the AVR is reset.

# Logique de démarrage

== Logique de démarrage ==

he main difference between the A-Star 32U4 Bootloader and Caterina is in the startup logic. This is the part of the bootloader that runs immediately after the AVR is reset, and it decides whether to run the user program or run the rest of the bootloader. The startup logic of the Caterina bootloader is designed so that when the RST line goes low, the bootloader will run. This means that if you want to restart your program using the RST line, it will take 8 seconds before the bootloader times out waiting for an upload and the sketch starts.

he main difference between the A-Star 32U4 Bootloader and Caterina is in the startup logic. This is the part of the bootloader that runs immediately after the AVR is reset, and it decides whether to run the user program or run the rest of the bootloader. The startup logic of the Caterina bootloader is designed so that when the RST line goes low, the bootloader will run. This means that if you want to restart your program using the RST line, it will take 8 seconds before the bootloader times out waiting for an upload and the sketch starts.

The start-up logic of the A-Star 32U4 Bootloader is shown in the flowchart below:

The start-up logic of the A-Star 32U4 Bootloader is shown in the flowchart below:

[[Fichier:Pololu-Romi-32U4-A-Star-Bootloader-01.jpg]]

[[Fichier:Pololu-Romi-32U4-A-Star-Bootloader-01.jpg]]

{{Pololu-Romi-32U4-TRAILER}}

{{Pololu-Romi-32U4-TRAILER}}