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fix: Fix buffering issues with CP2102 converter causing connection failures

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Some CP2102 drivers on Windows don't properly flush buffers after
unsupported commands, leaving stale data that breaks subsequent
communication. Add active buffer draining to read and discard any
lingering data before continuing.

Closes https://github.com/espressif/esptool/issues/1106
This commit is contained in:
Jaroslav Burian
2025-07-29 13:28:09 +02:00
parent 524825e25f
commit 5338ea054e
1 changed files with 28 additions and 3 deletions
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31
esptool/loader.py
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@@ -502,10 +502,35 @@ class ESPLoader(object):
if op is None or op_ret == op:
return val, data
if byte(data, 0) != 0 and byte(data, 1) == self.ROM_INVALID_RECV_MSG:
# Unsupported read_reg can result in
def drain_input_buffer(buffering_time=0.2):
"""
Actively drain the input buffer by reading data
for a specified time. Simple approach for some
drivers that have issues with the buffer flushing.
Args:
buffering_time: Time in seconds to wait for
the buffer to fill.
"""
time.sleep(buffering_time)
original_timeout = self._port.timeout
# Set a very short timeout for draining
self._port.timeout = 0.001
# Unsupported command response is sent 8 times and has
# 14 bytes length including delimiter 0xC0 bytes.
# At least part of it is read as a command response,
# but to be safe, read it all.
self._port.read(14 * 8)
# Restore original timeout
self._port.timeout = original_timeout
self.flush_input()
# Unsupported command can result in
# more than one error response for some reason
time.sleep(0.2) # Wait for input buffer to fill
self.flush_input() # Flush input buffer of hanging response
drain_input_buffer(0.2)
raise UnsupportedCommandError(self, op)
finally: