Merge pull request hdoordt#4 from stephen-nordic/main

Workaround get_metadata() failing to parse response; make start_measurement_matching capable of 100000 samples/second

Author: hdoordt

src/lib.rs

@@ -22,7 +22,7 @@ pub mod cmd;
 pub mod measurement;
 pub mod types;
 
-const SPS_MAX: usize = 90_000;
+const SPS_MAX: usize = 100_000;
 
 #[derive(Error, Debug)]
 /// PPK2 communication or data parsing error.
@@ -97,12 +97,31 @@ impl Ppk2 {
         Ok(response)
     }
 
-    /// Get the device metadata.
-    pub fn get_metadata(&mut self) -> Result<Metadata> {
+    fn try_get_metadata(&mut self) -> Result<Metadata> {
         let response = self.send_command(Command::GetMetaData)?;
         Metadata::from_bytes(&response)
     }
 
+    /// Get the device metadata.
+    pub fn get_metadata(&mut self) -> Result<Metadata> {
+        let mut result: Result<Metadata> = Err(Error::Parse("Metadata".to_string()));
+
+        // Retry a few times, as the metadata command sometimes fails
+        for _ in 0..3 {
+            match self.try_get_metadata() {
+                Ok(metadata) => {
+                    result = Ok(metadata);
+                    break;
+                }
+                Err(e) => {
+                    tracing::warn!("Error fetching metadata: {:?}. Retrying..", e);
+                }
+            }
+        }
+
+        result
+    }
+
     /// Enable or disable the device power.
     pub fn set_device_power(&mut self, power: DevicePower) -> Result<()> {
         self.send_command(Command::DeviceRunningSet(power))?;
@@ -161,7 +180,13 @@ impl Ppk2 {
                     .wait_while(lock.lock().unwrap(), |ready| !*ready)
                     .unwrap();
 
-                let mut buf = [0u8; 1024];
+                /* 4 bytes is the size of a single sample, and the PPK pushes 100,000 samples per second.
+                   Having size of `buf` at eg.1024 blocks port.read() until the buffer is full with 1024 bytes (128 samples).
+                   The measurement returned will be the average of the 128 samples. But we want to get every single sample when
+                   requested sps is 100,000. Hence, we set the buffer size to 4 bytes, and read the port in a loop,
+                   feeding the accumulator with the data.
+                */
+                let mut buf = [0u8; 4];
                 let mut measurement_buf = VecDeque::with_capacity(SPS_MAX);
                 let mut missed = 0;
                 loop {