adc/dac: make the buffer handling more symmetric

src/adc.rs

@@ -181,27 +181,37 @@ macro_rules! adc_input {
                 }
             }
 
-            /// Handle a transfer completion.
+            /// Obtain a buffer filled with ADC samples.
             ///
             /// # Returns
             /// A reference to the underlying buffer that has been filled with ADC samples.
-            pub fn transfer_complete_handler(
+            pub fn acquire_buffer(
                 &mut self,
-            ) -> &[u16; SAMPLE_BUFFER_SIZE] {
-                let next_buffer = self.next_buffer.take().unwrap();
-
+            ) -> &'static mut [u16; SAMPLE_BUFFER_SIZE] {
                 // Wait for the transfer to fully complete before continuing.
                 // Note: If a device hangs up, check that this conditional is passing correctly, as there is
                 // no time-out checks here in the interest of execution speed.
-                while self.transfer.get_transfer_complete_flag() == false {}
+                while !self.transfer.get_transfer_complete_flag() {}
+
+                let next_buffer = self.next_buffer.take().unwrap();
 
                 // Start the next transfer.
                 self.transfer.clear_interrupts();
                 let (prev_buffer, _) =
                     self.transfer.next_transfer(next_buffer).unwrap();
 
-                self.next_buffer.replace(prev_buffer);
-                self.next_buffer.as_ref().unwrap()
+                prev_buffer
+            }
+
+            /// Release a buffer of ADC samples to the pool.
+            ///
+            /// # Args
+            /// * `next_buffer` - Buffer of ADC samples to be re-used.
+            pub fn release_buffer(
+                &mut self,
+                next_buffer: &'static mut [u16; SAMPLE_BUFFER_SIZE],
+            ) {
+                self.next_buffer.replace(next_buffer); // .unwrap_none() https://github.com/rust-lang/rust/issues/62633
             }
         }
     };

src/dac.rs

@@ -116,18 +116,21 @@ macro_rules! dac_output {
                 }
             }
 
-            /// Mutably borrow the next output buffer to populate it with DAC codes.
-            pub fn prepare_buffer(&mut self) -> &mut [u16; SAMPLE_BUFFER_SIZE] {
-                self.next_buffer.as_mut().unwrap()
+            /// Acquire the next output buffer to populate it with DAC codes.
+            pub fn acquire_buffer(
+                &mut self,
+            ) -> &'static mut [u16; SAMPLE_BUFFER_SIZE] {
+                self.next_buffer.take().unwrap()
             }
 
             /// Enqueue the next buffer for transmission to the DAC.
             ///
             /// # Args
             /// * `data` - The next data to write to the DAC.
-            pub fn commit_buffer(&mut self) {
-                let next_buffer = self.next_buffer.take().unwrap();
-
+            pub fn release_buffer(
+                &mut self,
+                next_buffer: &'static mut [u16; SAMPLE_BUFFER_SIZE],
+            ) {
                 // If the last transfer was not complete, we didn't write all our previous DAC codes.
                 // Wait for all the DAC codes to get written as well.
                 if self.first_transfer {
@@ -135,7 +138,7 @@ macro_rules! dac_output {
                 } else {
                     // Note: If a device hangs up, check that this conditional is passing correctly, as
                     // there is no time-out checks here in the interest of execution speed.
-                    while self.transfer.get_transfer_complete_flag() == false {}
+                    while !self.transfer.get_transfer_complete_flag() {}
                 }
 
                 // Start the next transfer.
@@ -143,6 +146,7 @@ macro_rules! dac_output {
                 let (prev_buffer, _) =
                     self.transfer.next_transfer(next_buffer).unwrap();
 
+                // .unwrap_none() https://github.com/rust-lang/rust/issues/62633
                 self.next_buffer.replace(prev_buffer);
             }
         }

src/main.rs

@@ -745,12 +745,12 @@ const APP: () = {
     #[task(binds=DMA1_STR3, resources=[adcs, dacs, iir_state, iir_ch], priority=2)]
     fn process(c: process::Context) {
         let adc_samples = [
-            c.resources.adcs.0.transfer_complete_handler(),
-            c.resources.adcs.1.transfer_complete_handler(),
+            c.resources.adcs.0.acquire_buffer(),
+            c.resources.adcs.1.acquire_buffer(),
         ];
         let dac_samples = [
-            c.resources.dacs.0.prepare_buffer(),
-            c.resources.dacs.1.prepare_buffer(),
+            c.resources.dacs.0.acquire_buffer(),
+            c.resources.dacs.1.acquire_buffer(),
         ];
 
         for channel in 0..adc_samples.len() {
@@ -761,9 +761,12 @@ const APP: () = {
                 dac_samples[channel][sample] = y as i16 as u16 ^ 0x8000;
             }
         }
-
-        c.resources.dacs.0.commit_buffer();
-        c.resources.dacs.1.commit_buffer();
+        let [adc0, adc1] = adc_samples;
+        c.resources.adcs.0.release_buffer(adc0);
+        c.resources.adcs.0.release_buffer(adc1);
+        let [dac0, dac1] = dac_samples;
+        c.resources.dacs.0.release_buffer(dac0);
+        c.resources.dacs.1.release_buffer(dac1);
     }
 
     #[idle(resources=[net_interface, pounder, mac_addr, eth_mac, iir_state, iir_ch, afes])]