Subj : Re: uP port mapping To : Theo From : The Natural Philosopher Date : Fri Sep 13 2024 09:36:31 XPost: sci.electronics.design On 12/09/2024 22:28, Theo wrote: > In comp.sys.raspberry-pi john larkin wrote: >> RP2040 has I think 2 PIO blocks and each has a couple of hardware >> programmable state machines, and those can be set up to drive pins. >> I'm mostly concerned now with a PCB schematic design, picking the >> appropriate and easy-to-route pins from the CPU to things. >> >> My general question, for various processors, is how to associate bits >> in integer variables with physical pins on the chip. > > This is the function of a 'pinmux'. Different chips have different > capabilities of the pinmux, but it's rare to be able to connect any GPIO to > any pin - that's more FPGA territory. Typically the pinmux is just about > selecting one of multiple fixed functions for a given pin > (SPI1_MISO/I2C3_SDA/UART2_TX/...) > That is my understanding, too. What the pins do is programmable, but not tire mappings to specific registers inside the processor > So either you route your DAC to consecutive pins (D0 to GPIOn, D1 to n+1, > ..., ideally where n is a multiple of 8), or you're prepared to do the > necessary bit shuffling in software (which can be slow and non-atomic). I'd > suggest sticking to consecutive ordering if you can. > Yes. > (although I have no experience of the RP2xxx GPIO/PIO shenanigans) > I have - a very very little - but I have spent some time reading the docs to see at least if the Pi PICO is suitable for various speculative projects or not. There is a massive amount of shit it *can* do that probably only one person in a hundred would ever use. It just so happens that driving parallel connected external logic is something I have an interest in, so I read that bit... :-) > Theo -- Civilization exists by geological consent, subject to change without notice. – Will Durant --- SoupGate-Win32 v1.05 * Origin: Agency HUB, Dunedin - New Zealand | Fido<>Usenet Gateway (3:770/3) .