#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

Apache #NuttX RTOS helpfully provides a Skeleton Driver for I/O Expander ... Let's flesh it out for #PineDio Stack #BL604

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

Our #NuttX GPIO Expander for #BL604 implements these GPIO Operations: 1️⃣ Config / Read / Write GPIOs 2️⃣ Attach / Detach GPIO Interrupt Handlers 3️⃣ Handle GPIO Interrupts

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

At #NuttX Startup, our #BL604 GPIO Expander configures each Input / Output / Interrupt GPIO ... And registers the GPIOs as "/dev/gpioN"

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

Our #BL604 GPIO Expander for #NuttX RTOS will configure the GPIO Interrupts: Rising Edge Trigger vs Falling Edge Trigger

https://github.com/lupyuen/bl602_expander#set-gpio-options

#BL604 GPIO Expander for #NuttX calls the BL604 GPIO Driver to read GPIO Inputs and write GPIO Outputs ... Wonder what happens if we flip between Input and Output ... Like for #PineDio Stack's Push Button / Vibrator 🤔

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

How we attach a GPIO Interrupt Handler in our #BL604 GPIO Expander for #NuttX RTOS ... Only 1 Interrupt Hander per GPIO ... No Daisy Chaining for now 🌼⛓

https://github.com/lupyuen/bl602_expander#attach-gpio-interrupt

Our #BL604 GPIO Expander handles GPIO Interrupts in #NuttX RTOS ... By demuxing One Single IRQ into Multiple GPIOs

https://github.com/lupyuen/bl602_expander#handle-gpio-interrupt

Managing 23 GPIOs on #PineDio Stack #BL604 gets messy ... Our new GPIO Expander for Apache #NuttX RTOS can help! All shall be explained in this article

https://lupyuen.github.io/articles/expander?1

Why use a GPIO Expander? Because #BL604 looks like a Big Bag of GPIOs to Apache #NuttX RTOS

https://lupyuen.github.io/articles/expander?2

#BL602 EVB on Apache #NuttX RTOS ... And its strange limit of 3 GPIOs 🤔

https://lupyuen.github.io/articles/expander?3#bl602-evb-limitations

#BL602 EVB manages GPIO Pins in an awkward way on Apache #NuttX RTOS 🤔

https://lupyuen.github.io/articles/expander?4#pin-definitions

Here's how we'll fix the #BL604 GPIOs on Apache #NuttX RTOS ... With our new GPIO Expander

https://lupyuen.github.io/articles/expander?5#overcome-the-limitations

Apache #NuttX RTOS lets us create I/O Expanders that will manage many GPIOs ... Let's create one for #PineDio Stack #BL604

https://lupyuen.github.io/articles/expander?6#gpio-expander

Here are the #NuttX GPIO Operations supported by our #BL604 GPIO Expander

https://lupyuen.github.io/articles/expander?7#gpio-operations

Handling a #BL602 GPIO Interrupt on Apache #NuttX RTOS can get tricky ... Here's how we fixed it

https://lupyuen.github.io/articles/expander?8#gpio-interrupt

#BL602 GPIO Interrupts are multiplexed to One Single GPIO IRQ ... Which is a little harder to handle on Apache #NuttX RTOS

https://lupyuen.github.io/articles/expander?9#bl602-evb-interrupt

Here's how we call our #BL604 GPIO Expander ... To attach an Interrupt Handler in Apache #NuttX RTOS

https://lupyuen.github.io/articles/expander?10#attach-interrupt-handler

GPIO Command works great for testing #BL602 GPIO Interrupts in the #NuttX Shell

https://lupyuen.github.io/articles/expander?11#gpio-command

Here's how we load our #BL604 GPIO Expander at #NuttX Startup

https://lupyuen.github.io/articles/expander?15#load-gpio-expander