AVR Etherboot

An ethernet bootloader for the Atmel AVR microcontroller family.

Introduction

This project implements a bootloader for AVR ATMega 8bit microcontrollers, that loads the firmware via ethernet and uses the TFTP protocol. The goal is to reach a bootloader size of 2k words maximum to fit into the smaller members of the AVR family.

Supported devices

• ATMega32
• ATMega644
• ATMega64
• ATMega128
• ATMega256

Every AVR with at least 512k WORD bootloader flashsize should work.

Supported ethernet hardware

Currently the only supported ethernet hardware is the Microchip ENC28J60 ethernet controller. It communicates via the SPI bus with the ATmega and includes ethernet PHY/MAC in a single chip.

Functional description

We are developing two different versions of the bootloader:

• a small version which uses fixed addresses for itself and the TFTP server
• a medium version which implements a dhcp client for getting IP, TFTP-IP and filename of the firmware.
• (planned) a large version with enhanced features.

When the bootloader starts executing, the following actions take place:

• Load the parameters from EEPROM
• Initialize hardware peripherals
• (optional) Send DHCP request and process reply
• Send a TFTP Read Request to local IP broadcast address (or to address given by DHCP server)
• Process TFTP datapackets
  • Receive a datapacket
  • Decode Intel Hex file format
  • Program flash memory pages
• Jump to application (Address 0x0000)

See this page for a short introduction how to get started with the bootloader.