For whatever reason, Digikey and Mouser’s supply of the Atmega8-16 MCU is completely out of stock. I’ve seen differing reports whether this chip is End-Of-Life’d, but that certainly seems like it might be the case – neither site indicates that a future stock will be available. With this in mind, all new PSX64s produced will be using the Atmega168 instead. Really, this will functionally make no difference. The 168 can run faster and has more memory, but I’m driving it with the same 16 MHz crystal and with the same code. And luckily, the two chips are pin compatible, so no rework of the PCB is necessary.
The Atmega168 does have different fuses and slightly different architecture, and the firmware needed to be recompiled. I made a PSX64 with the ATmega168 tonight, and recompiled the firmware, and life is good. If you’re building a new board with an ATmega168, or (in the future) need to reflash your PSX64, the new revision B firmware is available here. (i.e. psx64fw11.hex is version 1.1 for the ATmega8, and psx64fw11b.hex is version 1.1 for the ATmega168).
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So is there any benefits to upgrading an older PSX64 to this new ATmega168? I know you mention that you are still using the same 16 MHz crystal and with the same code to drive it, but down the road for future upgrades or possible added features, what are your thoughts on this?
I know we talked about this already, but for anyone else who happens to be reading – it’s most likely that the extra memory will not be used by any new firmware revisions under the current board design. In the next physical board revision, there may be changes and updates that make use of it, but that won’t be for a while, and maybe not even then. So – ATmega8 PSX64 board owners are fine.