Be more consistent about DTR toggling (needed to reset serial devices).

davidgiven · May 1, 2024 · 653a6a0 · 653a6a0
1 parent f0b1b61
commit 653a6a0
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Showing 2 changed files with 27 additions and 16 deletions.
diff --git a/lib/usb/serial.cc b/lib/usb/serial.cc
@@ -42,11 +42,9 @@ class SerialPortImpl : public SerialPort
         commtimeouts.ReadIntervalTimeout = 100;
         SetCommTimeouts(_handle, &commtimeouts);
 
-        if (!EscapeCommFunction(_handle, CLRDTR))
-            error("Couldn't clear DTR: {}", get_last_error_string());
-        Sleep(200);
-        if (!EscapeCommFunction(_handle, SETDTR))
-            error("Couldn't set DTR: {}", get_last_error_string());
+        /* Toggle DTR to reset the device. */
+
+        toggleDtr();
 
         PurgeComm(_handle,
             PURGE_RXABORT | PURGE_RXCLEAR | PURGE_TXABORT | PURGE_TXCLEAR);
@@ -58,6 +56,15 @@ class SerialPortImpl : public SerialPort
     }
 
 public:
+    void toggleDtr() override
+    {
+        if (!EscapeCommFunction(_handle, CLRDTR))
+            error("Couldn't clear DTR: {}", get_last_error_string());
+        Sleep(200);
+        if (!EscapeCommFunction(_handle, SETDTR))
+            error("Couldn't set DTR: {}", get_last_error_string());
+    }
+
     ssize_t readImpl(uint8_t* buffer, size_t len) override
     {
         DWORD rlen;
@@ -98,11 +105,7 @@ class SerialPortImpl : public SerialPort
             .StopBits = ONESTOPBIT};
         SetCommState(_handle, &dcb);
 
-        if (!EscapeCommFunction(_handle, CLRDTR))
-            error("Couldn't clear DTR: {}", get_last_error_string());
-        Sleep(200);
-        if (!EscapeCommFunction(_handle, SETDTR))
-            error("Couldn't set DTR: {}", get_last_error_string());
+        toggleDtr();
     }
 
 private:
@@ -163,12 +166,7 @@ class SerialPortImpl : public SerialPort
 
         /* Toggle DTR to reset the device. */
 
-        int flag = TIOCM_DTR;
-        if (ioctl(_fd, TIOCMBIC, &flag) == -1)
-            error("cannot clear DTR on serial port: {}", strerror(errno));
-        usleep(200000);
-        if (ioctl(_fd, TIOCMBIS, &flag) == -1)
-            error("cannot set DTR on serial port: {}", strerror(errno));
+        toggleDtr();
 
         /* Flush pending input from a generic greaseweazel device */
         tcsetattr(_fd, TCSAFLUSH, &t);
@@ -180,6 +178,16 @@ class SerialPortImpl : public SerialPort
     }
 
 public:
+    void toggleDtr() override
+    {
+        int flag = TIOCM_DTR;
+        if (ioctl(_fd, TIOCMBIC, &flag) == -1)
+            error("cannot clear DTR on serial port: {}", strerror(errno));
+        usleep(200000);
+        if (ioctl(_fd, TIOCMBIS, &flag) == -1)
+            error("cannot set DTR on serial port: {}", strerror(errno));
+    }
+
     ssize_t readImpl(uint8_t* buffer, size_t len) override
     {
         ssize_t rlen = ::read(_fd, buffer, len);
@@ -204,6 +212,8 @@ class SerialPortImpl : public SerialPort
         tcgetattr(_fd, &t);
         cfsetspeed(&t, baudRate);
         tcsetattr(_fd, TCSANOW, &t);
+
+        toggleDtr();
     }
 
 private:

diff --git a/lib/usb/serial.h b/lib/usb/serial.h
@@ -11,6 +11,7 @@ class SerialPort
     virtual ssize_t readImpl(uint8_t* buffer, size_t len) = 0;
     virtual ssize_t write(const uint8_t* buffer, size_t len) = 0;
     virtual void setBaudRate(int baudRate) = 0;
+    virtual void toggleDtr() = 0;
 
     void read(uint8_t* buffer, size_t len);
     void read(Bytes& bytes);