In the end this code base is what I am trying to get working # define SIGRD 5 // this is missing from some of the io.h files, this is a hack so avr/boot.And am attempting to pipe it through a Trinket Pro 5V ( have a 3V model if that is neccessary) # define MCUSR MCUCSR // hack for enabling ATmega8 support These instructions are protected from being overwritten by this code.Ī magic byte at the bottom of the stack is checked to see where to jump when the PCINT ISR fires.
The page before the BOOTLOADER_ADDRESS is used to store 2 additional jump vectors that jumps into the user app, therefor these jump instructions must not be used by the userapp. The two jumps inside this region is protected from being overwritten by this code. The jump table is generated by "jump.asm", this file ensures that the bootloader is executed first before the userapp, and that PCINT is targeted within the bootloader first. The datasheet says each flash operation will take a maximum of 4.5msĪnother challenge is how to retarget the interrupt jump table. The CPU will be halted during flash operations, so you do not need to wait for SPM to finish, but interrupts must be disabled before calling SPM because it can only be called within 4 cycles of writing to SPMCSR A small change to nf to extend the delays to make this less of a problem but it is still a problem. This fact is why it will miss USB communication during flash operations. This chip does not have RWW, so the CPU is halted during flash erase and write. This code also borrows from, but using USBtiny protocol instead of USBasp You should have received a copy of the GNU Lesser General Public GNU Lesser General Public License for more details. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
GemmaBoot is distributed in the hope that it will be useful,īut WITHOUT ANY WARRANTY without even the implied warranty of The License, or (at your option) any later version. Published by the Free Software Foundation, either version 3 of It under the terms of the GNU Lesser General Public License as GemmaBoot is free software: you can redistribute it and/or modify * This code is heavily derived from USBaspLoader, but also from USBtiny, with USBtinyISP's settings * Gemma (from Adafruit Industries) will use GemmaBoot * GemmaBoot by GemmaBoot is a bootloader that emulates a USBtinyISP (from Adafruit Industries)
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