#PineDio Stack #BL604 has an interesting problem on Apache #NuttX RTOS ... Too many GPIOs! Let's make it work 👍

https://github.com/lupyuen/bl602_expander

#BL602 EVB on #NuttX supports one GPIO Input, one GPIO Output and one GPIO Interrupt ... And names them sequentially: "/dev/gpio0", "/dev/gpio1", "/dev/gpio2" ... Which gets super confusing because "/dev/gpio0" doesn't map to BL602 GPIO Pin 0 🤔

https://github.com/lupyuen/bl602_expander#bl602-evb-limitations

What happens when we try to support 23 GPIOs on #PineDio Stack #BL604? Yep the GPIO Names will look really messy on #NuttX RTOS 🤔

https://github.com/lupyuen/bl602_expander#bl602-evb-limitations

All 23 GPIOs are fully wired up on #PineDio Stack #BL604! 😲 Let's simplify #NuttX and rename the GPIOs as "/dev/gpio0" to "/dev/gpio22" ... Easier for devs to create NuttX Drivers 👍

https://github.com/lupyuen/bl602_expander#bl602-evb-limitations

Apache #NuttX RTOS lets us create I/O Expander Drivers that will handle many GPIOs (Input / Output / Interrupt) ... Perfect for #PineDio Stack #BL604!

https://github.com/lupyuen/bl602_expander#gpio-expander

Handling GPIO Interrupts gets tricky on #PineDio Stack #BL604 ... All GPIO Interrupts are multiplexed into a single IRQ! Our #NuttX GPIO Expander can help

https://github.com/lupyuen/bl602_expander#gpio-interrupts

As noted (eloquently) by Robert Lipe, attaching a #BL602 GPIO Interrupt Handler is hard (because our stars are misaligned) ... Let's fix this with our GPIO Expander for Apache #NuttX RTOS

https://github.com/lupyuen/bl602_expander#gpio-interrupts

Tracking all 23 GPIOs used by #PineDio Stack #BL604 can get challenging ... We might reuse GPIOs by mistake! 😱 Our #NuttX GPIO Expander shall validate the GPIOs at startup

https://github.com/lupyuen/bl602_expander#check-reused-gpios

Someday our #NuttX GPIO Expander for #BL604 shall validate that the SPI / I2C / UART Pin Functions are correctly assigned to the GPIO Pin Numbers ... So SPI MISO must be either GPIO 0, 4, 8, 12, 16 or 20

https://github.com/lupyuen/bl602_expander#validate-pin-functions

@lupyuen

Can we static assert to avoid overheads in nuttx?
(Ie prevent builds with bad allocations)

@Ralim Hmmm maybe. But we still need a runtime check to be sure that the GPIOs are not reused

@lupyuen hmm true. I just like having configurations checked at compile time where possible to save iterations of testing :)

@Ralim Here's how we might validate the BL602 Pin Functions at Compile Time...

https://github.com/lupyuen/bl602_expander#validate-pin-functions