Allow restoring PWM back to default

Signed-off-by: Daniel Schaefer <[email protected]>

src/lib.rs

@@ -28,7 +28,7 @@ where
     I2C: Read<Error = I2cError>,
 {
     /// Fill all pixels of the display at once. The brightness should range from 0 to 255.
-    /// brightness slice must have 0xC5 elements
+    /// brightness slice must have 0xC6 elements
     pub fn fill_matrix(&mut self, brightnesses: &[u8]) -> Result<(), I2cError> {
         // Extend by one, to add address to the beginning
         let mut buf = [0x00; 0xC7];
@@ -39,6 +39,15 @@ where
         Ok(())
     }
 
+    /// Read back the currently displayed matrix
+    pub fn read_matrix(&mut self) -> Result<[u8; 0xC6], I2cError> {
+        let mut buf = [0x00; 0xC6];
+        self.bank(Page::Pwm)?;
+        self.i2c.write(self.address, &[0x01])?;
+        self.i2c.read(self.address, &mut buf)?;
+        Ok(buf)
+    }
+
     /// Fill the display with a single brightness. The brightness should range from 0 to 255.
     pub fn fill(&mut self, brightness: u8) -> Result<(), I2cError> {
         self.bank(Page::Pwm)?;
@@ -91,12 +100,33 @@ where
     /// Send a reset message to the slave device. Delay is something that your device's HAL should
     /// provide which allows for the process to sleep for a certain amount of time (in this case 10
     /// MS to perform a reset).
+    /// This will result in all registers being restored to their defaults.
     pub fn reset<DEL: DelayMs<u8>>(&mut self, delay: &mut DEL) -> Result<(), I2cError> {
         self.write_register(Page::Config, addresses::RESET_REGISTER, addresses::RESET)?;
         delay.delay_ms(10);
         Ok(())
     }
 
+    /// Reset the controller and restore all registers
+    pub fn reset_restore<DEL: DelayMs<u8>>(
+        &mut self,
+        delay: &mut DEL,
+    ) -> Result<(), Error<I2cError>> {
+        // Back up registers
+        let prev_config = self.read_register(Page::Config, addresses::CONFIG_REGISTER)?;
+        // Assumes all scaling registers are set to the same value
+        let prev_scale = self.read_register(Page::Scale, 0x01)?;
+        let prev_brightness = self.read_matrix()?;
+
+        self.setup(delay)?;
+
+        // Restore registers
+        self.write_register(Page::Config, addresses::CONFIG_REGISTER, prev_config)?;
+        self.set_scaling(prev_scale)?;
+        self.fill_matrix(&prev_brightness)?;
+        Ok(())
+    }
+
     /// Set the current available to each LED. 0 is none, 255 is the maximum available
     pub fn set_scaling(&mut self, scale: u8) -> Result<(), I2cError> {
         self.bank(Page::Scale)?;
@@ -126,7 +156,17 @@ where
     }
 
     /// Set the PWM frequency
-    pub fn set_pwm_freq(&mut self, pwm: PwmFreq) -> Result<(), I2cError> {
+    pub fn set_pwm_freq<DEL: DelayMs<u8>>(
+        &mut self,
+        delay: &mut DEL,
+        pwm: PwmFreq,
+    ) -> Result<(), Error<I2cError>> {
+        // The default frequency, can't set it. Reset the controller and restore the registers
+        if let PwmFreq::P29k = pwm {
+            self.reset_restore(delay)?;
+            return Ok(());
+        }
+
         // Enter test mode
         self.write_register(Page::Config, addresses::TEST_MODE_REGISTER, 0x01)?;
 
@@ -220,6 +260,9 @@ enum Page {
 
 #[repr(u8)]
 pub enum PwmFreq {
+    /// 29kHz, the default. To set this, it'll reset the controller
+    P29k = 0xFF,
+    /// 31.25kHz
     P31k25 = 0xE0,
     /// 15.6kHz
     P15k6 = 0x20,
@@ -232,7 +275,7 @@ pub enum PwmFreq {
     /// 977Hz
     P977 = 0xA0,
     /// 488Hz
-    P448 = 0xC0,
+    P488 = 0xC0,
 }
 
 #[repr(u8)]