The example programs
For each platform, the goal is to implement four test programs, of increasing complexity, starting where possible from pre-defined examples. (Because everyone starts by copying examples. Starting from a blank page/empty project directory triggers too much existential angst.) None of these programs are complicated. They should be easy to write. But I know that they probably won't be, because everything is more complicated than you expect. It's quite possible that I'll only get so far with some of these and will abandon if things get too hard on any particular platform.
As I go through developing and testing these things for each platform, I'll keep track of the highs and lows of using the platform, using a set of criteria listed in the next section.
Example 1: Blinky
The nRF52840 development kit has LEDs. Let's make them blink.
- Installation and setup of platform.
- Setting up a new project.
- Configure, build, flash.
- Default clock and power setup.
- Simple delays in single-threaded code.
This one really should just be a case of picking an existing example, building and flashing it.
Example 2: PWM blinky with programmable duty cycle
PWM dimming of that LED. The nRF52840 has the usual sort of PWM timers.
Here we're going to introduce a methodology I'm going to apply for all of these more complex examples, which is to take more than one route to get to the final code. Here, there are two things to look at:
- Use a pre-defined PWM example: this will give a clear demonstration that the thing we're trying to do is possible.
- Add PWM dimming to the basic blinky form Example 1: the idea here is to extend an existing code to use new functionality.
- Maybe more on clock setup.
- Timer setup for PWM.
There's not that much new functionality in this example, but it's intended to explore how easy it is to add new functionality based on documentation and examples provided. This is one of the things that proved most difficult using the Nordic nRF5 SDK, and it seems like a fairly critical thing to be able to do.
Example 3: BLE-enabled PWM blinky
Now we're getting to the fun stuff. Control a PWM dimmed LED via Bluetooth. We'll use Nordic's nRF Connect for Mobile Android application to talk to code running on the nRF52840 development kit.
There are two ways to go at this:
- Add BLE to the PWM blinky from Example 2.
- Add PWM blinky functionality to a pre-defined BLE example.
- Maybe device conflicts: I'll see if I can organise things so that the PWM blinky uses a timer that the Bluetooth library uses to see if the toolset warns me about that.
I'll also check out a pre-defined BLE example, since Bluetooth setup is kind of complicated and it would be interesting to see how the different toolsets handle this.
Example 4: Something Almost Realistic
The idea here is to have a little application using an RTOS to do a few different things at once, some of them involving Bluetooth communications, but also including a bit of computation and a bit of external I/O. This is about the minimum useful set of functionality I can imagine for any kind of IoT or similar device.
What this thing will do:
- PWM blinky with BLE remote control (so building on Example 3);
- Generate digits of π in a separate RTOS task and publish them via BLE;
- Use a GPIO button to switch digit generation on and off (with temporary timed interruption of the PWM blinky as "UI feedback").
- Asynchronous GPIO input.
- Multi-threaded access to BLE communications.