Improve synchronize_mpsse timeout handling.

CHANGELOG.md

@@ -4,6 +4,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.23.0] - 2020-10-23
+### Changed
+- `synchronize_mpsse` will now timeout if no read data is recieved and a read
+  timeout has been set.
+
 ## [0.22.0] - 2020-10-15
 ### Added
 - Added `list_devices_fs` to work around vendor driver bug.
@@ -51,7 +56,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Prior releases
 A changelog was not kept for prior releases.
 
-[Unreleased]: https://github.com/newAM/libftd2xx-rs/compare/0.21.1...HEAD
+[Unreleased]: https://github.com/newAM/libftd2xx-rs/compare/0.23.0...HEAD
+[0.23.0]: https://github.com/newAM/libftd2xx-rs/releases/tag/0.23.0
+[0.22.0]: https://github.com/newAM/libftd2xx-rs/releases/tag/0.22.0
 [0.21.1]: https://github.com/newAM/libftd2xx-rs/releases/tag/0.21.1
 [0.21.0]: https://github.com/newAM/libftd2xx-rs/releases/tag/0.21.0
 [0.20.0]: https://github.com/newAM/libftd2xx-rs/releases/tag/0.20.0

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "libftd2xx"
-version = "0.22.0" # remember to update html_root_url
+version = "0.23.0" # remember to update html_root_url
 authors = ["Alex M. <[email protected]>"]
 edition = "2018"
 description = "Rust safe wrapper around the libftd2xx-ffi crate."

README.md

@@ -17,7 +17,7 @@ permission from FTDI.
 
 ```toml
 [dependencies]
-libftd2xx = "~0.22.0"
+libftd2xx = "~0.23.0"
 ```
 
 This is a basic example to get your started.

src/lib.rs

@@ -10,7 +10,7 @@
 //!
 //! ```toml
 //! [dependencies]
-//! libftd2xx = "~0.22.0"
+//! libftd2xx = "~0.23.0"
 //! ```
 //!
 //! This is a basic example to get your started.
@@ -74,7 +74,7 @@
 //! [libftd2xx-ffi]: https://github.com/newAM/libftd2xx-ffi-rs
 //! [setup executable]: https://www.ftdichip.com/Drivers/CDM/CDM21228_Setup.zip
 //! [udev]: https://en.wikipedia.org/wiki/Udev
-#![doc(html_root_url = "https://docs.rs/libftd2xx/0.22.0")]
+#![doc(html_root_url = "https://docs.rs/libftd2xx/0.23.0")]
 #![deny(missing_docs)]
 
 mod errors;

src/mpsse.rs

@@ -513,10 +513,14 @@ pub trait FtdiMpsse: FtdiCommon {
         self.set_bit_mode(settings.mask, BitMode::Mpsse)?;
         self.enable_loopback()?;
         self.synchronize_mpsse()?;
-        self.disable_loopback()?;
+
+        // bundle the disable loopback and clock divisor writes together
+        // to save some time
+        let mut mpsse_cmd = MpsseCmdBuilder::new().disable_loopback();
         if let Some(frequency) = settings.clock_frequency {
-            self.set_clock(frequency)?;
+            mpsse_cmd = mpsse_cmd.set_clock(frequency, Self::DEVICE_TYPE);
         }
+        self.write(mpsse_cmd.as_slice())?;
 
         Ok(())
     }
@@ -550,28 +554,19 @@ pub trait FtdiMpsse: FtdiCommon {
     /// [FTDI MPSSE Basics]: https://www.ftdichip.com/Support/Documents/AppNotes/AN_135_MPSSE_Basics.pdf
     fn synchronize_mpsse(&mut self) -> Result<(), TimeoutError> {
         self.purge_rx()?;
+        debug_assert_eq!(self.queue_status()?, 0);
         self.write(&[ECHO_CMD_2])?;
 
-        let mut num_bytes: usize = 0;
-        while num_bytes == 0 {
-            num_bytes = self.queue_status()?;
-        }
-
-        let mut buf = vec![0; num_bytes].into_boxed_slice();
+        // the FTDI MPSSE basics polls the queue status here
+        // we purged the RX buffer so the response should always be 2 bytes
+        // this allows us to leverage the timeout built into read
+        let mut buf: [u8; 2] = [0; 2];
         self.read(&mut buf)?;
 
-        let mut command_echoed = false;
-        for count in 0..(num_bytes - 1) {
-            if buf[count] == 0xFA && buf[count + 1] == ECHO_CMD_2 {
-                command_echoed = true;
-                break;
-            }
-        }
-
-        if !command_echoed {
-            Err(TimeoutError::from(FtStatus::OTHER_ERROR))
-        } else {
+        if buf[0] == 0xFA && buf[1] == ECHO_CMD_2 {
             Ok(())
+        } else {
+            Err(TimeoutError::from(FtStatus::OTHER_ERROR))
         }
     }