Fix frame ACK being discarded by flush_input after write#28
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The retry loop did write() → flush_input() → read(ACK), which discarded ACKs the device sent during/right after the write. Every frame needed 4-5 attempts, wasting ~80% of transfer time. Fix: flush_input() → write() → read(ACK). Clear stale data before sending, not after. Before: CV300 131KB in 259s (0.9 KB/s), EV300 236KB in 263s (0.9 KB/s) After: CV300 131KB in 40s (3.3 KB/s), EV300 236KB in 66s (3.5 KB/s) Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Problem
The frame retry loop did
write(frame) → flush_input() → read(ACK). The device responds fast enough that the ACK arrives during or right after the write.flush_input()then discards it, forcing a retry. Every frame needed 4-5 attempts, wasting ~80% of transfer time.Note:
burn(the reference tool) has the same bug insendframe().Fix
One-line change: move
flush_input()beforewrite()instead of after.Benchmarks (real hardware)
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