2 files changed, 34 insertions(+), 28 deletions(-)

M src/cp437.rs
M src/main.rs

@@ 3,7 3,7 @@
 
 // Also see: https://github.com/riyas-org/max7219/blob/master/max7219-rpi/src/transitions.py
 
-pub(crate) static cp437_FONT: [[u8; 8]; 256] = [
+pub(crate) static CP437_FONT: [[u8; 8]; 256] = [
     [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00], // 0x00
     [0x7E, 0x81, 0x95, 0xB1, 0xB1, 0x95, 0x81, 0x7E], // 0x01
     [0x7E, 0xFF, 0xEB, 0xCF, 0xCF, 0xEB, 0xFF, 0x7E], // 0x02

@@ 1,22 1,16 @@
-//! Blinks the LED on a Pico board
+//! Display a scrolling message on an 8x8 LED matrix.
 //!
-//! This will blink an LED attached to GP25, which is the pin the Pico uses for the on-board LED.
+//! Uses the Pico SPI interface to communicate with a MAX7219
 #![no_std]
 #![no_main]
 
 use cortex_m_rt::entry;
-use defmt::*;
 use defmt_rtt as _;
-use embedded_hal::digital::v2::OutputPin;
 use embedded_hal::spi::FullDuplex;
 use embedded_time::fixed_point::FixedPoint;
 use embedded_time::rate::Extensions;
 use panic_probe as _;
-
-// Provide an alias for our BSP so we can switch targets quickly.
-// Uncomment the BSP you included in Cargo.toml, the rest of the code does not need to change.
 use rp_pico as bsp;
-// use sparkfun_pro_micro_rp2040 as bsp;
 
 use bsp::hal::{
     clocks::{init_clocks_and_plls, Clock},


@@ 27,7 21,15 @@ use bsp::hal::{
 };
 
 mod cp437;
-use cp437::cp437_FONT;
+use cp437::CP437_FONT;
+
+// Refer Page 7 of:
+// https://datasheets.maximintegrated.com/en/ds/MAX7219-MAX7221.pdf
+const MAX7219_REG_DECODEMODE:u8  = 0x9;
+const MAX7219_REG_INTENSITY:u8   = 0xA;
+const MAX7219_REG_SCANLIMIT:u8   = 0xB;
+const MAX7219_REG_SHUTDOWN:u8    = 0xC;
+const MAX7219_REG_DISPLAYTEST:u8 = 0xF;
 
 struct Max7219<D>
 where


@@ 45,34 47,39 @@ where
         Max7219 { spi: s, delay: d }
     }
 
+    fn spi_write(&mut self, reg: u8, val: u8) {
+        let _ = self.spi.send(((reg as u16) << 8) + val as u16);
+        self.delay.delay_ms(1);
+    }
+
     fn init(&mut self) {
-        self.spi.send(0x0b07);
-        self.spi.send(0x0900);
-        self.spi.send(0x0f00);
-        // intensity = 10
-        self.spi.send(0x0a0a);
+        self.spi_write(MAX7219_REG_SCANLIMIT, 7);
+        // Control individual pixels
+        self.spi_write(MAX7219_REG_DECODEMODE, 0);
+        self.spi_write(MAX7219_REG_DISPLAYTEST, 0);
+        // intensity
+        self.spi_write(MAX7219_REG_INTENSITY, 0xa);
         // not in shutdown mode
-        self.spi.send(0x0c01);
+        self.spi_write(MAX7219_REG_SHUTDOWN, 1);
     }
 
     fn clear(&mut self) {
         for col in 1..9 {
-            self.spi.send((col as u16) << 8);
-            self.delay.delay_ms(1);
+            self.spi_write(col as u8, 0u8);
         }
     }
 
     fn scroll_left(&mut self, from_char: u8, to_char: u8, font: &[[u8; 8]]) {
-        let mut data = 0u16;
+        let mut data:u8;
         for i in 0..8 {
             self.delay.delay_ms(90);
             for col in 0..8 {
                 if (col + i) < 8 {
-                    data = font[from_char as usize][col + i] as u16;
+                    data = font[from_char as usize][col + i];
                 } else {
-                    data = font[to_char as usize][col + i - 8] as u16;
+                    data = font[to_char as usize][col + i - 8];
                 }
-                self.spi.send(((col as u16 + 1) << 8) + data);
+                self.spi_write((col + 1) as u8, data);
                 self.delay.delay_ms(1);
             }
         }


@@ 84,7 91,7 @@ where
             self.scroll_left(prev as u8, curr as u8, font);
             prev = curr;
         }
-        self.scroll_left(prev as u8, ' ' as u8, font);
+        self.scroll_left(prev as u8, b' ', font);
     }
 }
 


@@ 116,7 123,7 @@ fn main() -> ! {
         &mut pac.RESETS,
     );
 
-    let mut delay = cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().integer());
+    let  delay = cortex_m::delay::Delay::new(core.SYST, clocks.system_clock.freq().integer());
 
     let _spi1_sck = pins.gpio14.into_mode::<bsp::hal::gpio::FunctionSpi>();
     let _spi1_tx = pins.gpio15.into_mode::<bsp::hal::gpio::FunctionSpi>();


@@ 124,7 131,7 @@ fn main() -> ! {
 
     let spi = bsp::hal::Spi::<_, _, 16>::new(pac.SPI1);
     // Exchange the uninitialised SPI driver for an initialised one
-    let mut spi = spi.init(
+    let  spi = spi.init(
         &mut pac.RESETS,
         clocks.peripheral_clock.freq(),
         1_000_000u32.Hz(),


@@ 135,9 142,8 @@ fn main() -> ! {
 
     max7219.init();
     max7219.clear();
+
     loop {
-        max7219.show_message("Happy New Year @rustembedded !!", &cp437_FONT);
+        max7219.show_message("Happy New Year @rustembedded !!", &CP437_FONT);
     }
-
-    loop {}
 }