Init function

Now that we have defined all the necessary functions, we are almost done with the driver. The last function we need to implement is the init method.

After the user creates an instance of the Max7219 driver, they must call this init function to perform the basic initialization of the MAX7219 chip. This sets up the device with a default state, ready for use.

The init function does the following:

• Powers on all devices in the chain
• Disables the test mode on all devices
• Sets the scan limit to cover all digits
• Sets decode mode to NoDecode (raw data mode)
• Clears all display digits

#![allow(unused)]
fn main() {
pub fn init(&mut self) -> Result<()> {
    self.power_on()?;

    self.test_all(false)?;
    self.set_scan_limit_all(NUM_DIGITS)?;
    self.set_decode_mode_all(DecodeMode::NoDecode)?;

    self.clear_all()?;

    Ok(())
}
}

Hoorah! We have finally completed our driver.

Completed Project

I have made a simple driver project that follows everything we explained in this book. You can find it here: https://github.com/ImplFerris/max7219-driver-project.

If you run into any errors while compiling or want to see a complete example, this project should be helpful.

Where to Go From Here?

As i mentioned earlier, I have created a full-featured crate called max7219-display that provides easy-to-use utility functions to control both LED matrix and 7-segment displays. It is published on crates.io here

We didn't cover this crate in detail because it's outside the scope of writing a low-level driver; it builds on top of the bare-driver we created in this book.

As an exercise, you can explore the crate's features and usage by checking out its documentation here

You can also find the full source code on GitHub here:
https://github.com/ImplFerris/max7219-display