Program full sectors, longer read/write timeouts

programmer/.gitignore

@@ -9,6 +9,10 @@ __pycache__/
 *~
 tinyprog/full_version.py
 
+# due to pip install . (for development)
+# https://github.com/pypa/pip/issues/6213
+pip-wheel-metadata
+
 # due to using tox and pytest
 .tox
 .coverage

programmer/tinyprog/__init__.py

@@ -113,9 +113,20 @@ def __str__(self):
         return self.port_name
 
     def __enter__(self):
+        # Timeouts:
+        # - Read:  2.0 seconds (timeout)
+        # - Write: 5.0 seconds (writeTimeout)
+        #
+        # Rationale: hitting the writeTimeout is fatal, so it pays to be
+        # patient in case there is a brief delay; readTimeout is less
+        # fatal, but can result in short reads if it is hit, so we want
+        # a timeout high enough that is never hit normally.  In practice
+        # 1.0 seconds is *usually* enough, so the chosen values are double
+        # and five times the "usually enough" values.
+        #
         try:
             self.ser = serial.Serial(
-                self.port_name, timeout=1.0, writeTimeout=1.0).__enter__()
+                self.port_name, timeout=2.0, writeTimeout=5.0).__enter__()
         except serial.SerialException as e:
             raise PortError("Failed to open serial port:\n%s" % str(e))
 
@@ -499,6 +510,22 @@ def program_sectors(self, addr, data):
                 for minor_offset in range(0, 4 * 1024, minor_sector_size):
                     minor_write_data = current_write_data[
                         minor_offset:minor_offset + minor_sector_size]
+
+                    # The TinyFPGA firmware and/or flash chip does not handle
+                    # partial minor sector writes properly, so pad out short
+                    # writes to a whole minor sector.  (This is safe because
+                    # we explicitly erased the whole sector above, so the
+                    # following bytes must be freshly erased.  Usually it will
+                    # only happen on the final minor sector to be written.)
+                    #
+                    if (len(minor_write_data) < minor_sector_size):
+                         pad_len = minor_sector_size - len(minor_write_data)
+                         padding = b'\xff' * pad_len
+
+                         minor_write_data = bytearray(minor_write_data)
+                         minor_write_data.extend(padding)
+                         assert(len(minor_write_data) == minor_sector_size)
+
                     self.write(
                         current_addr + minor_offset,
                         minor_write_data,