Using postcard for complete serialization

src/hardware/flash.rs

@@ -2,7 +2,7 @@ use core::fmt::Write;
 use embedded_storage::nor_flash::{NorFlash, ReadNorFlash};
 use stm32h7xx_hal::flash::{LockedFlashBank, UnlockedFlashBank};
 
-#[derive(miniconf::Tree)]
+#[derive(serde::Serialize, serde::Deserialize, miniconf::Tree)]
 pub struct Settings {
     pub broker: heapless::String<255>,
     pub id: heapless::String<23>,
@@ -30,34 +30,16 @@ impl FlashSettings {
         mut flash: LockedFlashBank,
         mac: smoltcp_nal::smoltcp::wire::EthernetAddress,
     ) -> Self {
-        let mut settings = Settings::new(mac);
         let mut buffer = [0u8; 512];
         flash.read(0, &mut buffer[..]).unwrap();
 
-        let mut data = &buffer[..];
-
-        // We iteratively read the settings from flash to allow for easy expansion of the settings
-        // without losing data in the future when new fields are added.
-        settings.broker = {
-            match postcard::take_from_bytes(data) {
-                Ok((item, remainder)) => {
-                    data = remainder;
-                    item
-                }
-                Err(e) => {
-                    log::warn!("Failed to decode broker from flash settings memory - using default: {e:?}");
-                    settings.broker
-                }
-            }
-        };
-
-        settings.id = {
-            match postcard::from_bytes(data) {
-                Ok(item) => item,
-                Err(e) => {
-                    log::warn!("Failed to MQTT ID from flash settings memory - using default: {e:?}");
-                    settings.id
-                }
+        let settings = match postcard::from_bytes(&buffer) {
+            Ok(settings) => settings,
+            Err(_) => {
+                log::warn!(
+                    "Failed to load settings from flash. Using defaults"
+                );
+                Settings::new(mac)
             }
         };
 
@@ -68,16 +50,8 @@ impl FlashSettings {
         let mut bank = self.flash.unlocked();
 
         let mut data = [0; 512];
-        let mut offset: usize = 0;
-        offset +=
-            postcard::to_slice(&self.settings.broker, &mut data[offset..])
-                .unwrap()
-                .len();
-        offset += postcard::to_slice(&self.settings.id, &mut data[offset..])
-            .unwrap()
-            .len();
-
+        let serialized = postcard::to_slice(&self.settings, &mut data).unwrap();
         bank.erase(0, UnlockedFlashBank::ERASE_SIZE as u32).unwrap();
-        bank.write(0, &data[..offset]).unwrap();
+        bank.write(0, serialized).unwrap();
     }
 }