Swift for Arduino

 BOOTLOADERS *** Some interesting general boot loader facts: The Boot Loader is basically a section at the top of flash memory, how big it is depends on the BOOTSZ1 and BOOTSZ0 bits in the Low Fuse byte. It has the special property that ONLY while the core is running instructions in the bootloader, a special instruction called SPM will function. This function allows writing data to the flash memory. As normal with all flash, you need to erase the page you are writing first, otherwise your write operation will often not function correctly. I think you can change 1 bits to 0 bits but not the other way around, which is true for all flash writing. So the flash erase process always sets a flash memory page to all 0xFF (all 1 bits) The usual way the boot loader runs is if the fuse bit BOOTRST is active (i.e. it reads as a 0!) then when the MCU is reset, it will start execution at the beginning of the bootloader (as defined above). If the bit is not set, it will start execution at 0x0000....

 The nice thing about Swift for Arduino these days is we are having a lot of conversations like "exactly how much performance can you get from an atmega328p, how much program space is the limit? what about RAM?" To me it shows we've gone far beyond the 'hobbyist' place we started from and now as we build professional products, we are dealing with the same issues all professional embedded developers grapple with... in a word efficiency. To that end I thought it might be worth me putting down some thoughts on what some of the numbers are, where the overheads are, what are the limits on RAM and program memory? I'm talking here to the atmega328p as that's what most of our work uses.. the classic Arduino UNO heart, but of course similar things would apply for other chips. In spec, we have 2k RAM, 32k program memory? Can I use all of those? Of course not. ;-) Let's break it down. PROGRAM MEMORY You might have seen my earlier article with a breakdown of what ...