Improve flash reliability at high baud rates; update stubs to v1.1.0 - #58
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Signed-off-by: deadprogram <ron@hybridgroup.com>
Signed-off-by: deadprogram <ron@hybridgroup.com>
The esp-flasher-stub v1.1.0 uses double-buffering: it ACKs each flash data block immediately, then writes to flash as a post-process. During flash writes the ESP32 ROM disables interrupts (SPI bus shared with cache), causing the 128-byte UART FIFO to overflow if the next block arrives too soon. Additionally, USB-UART bridges occasionally lose bytes at 460800 baud, producing truncated SLIP frames. Fix with three complementary changes: - Add port.Drain() to sendCommand to ensure each frame is physically committed to the USB-UART bridge before proceeding. - Add a post-process delay (waitForStubFlashWrite) after each flash block ACK proportional to the estimated page count, giving the stub time to finish its flash write before new data arrives. - Retry flash block writes on both TimeoutError and retryable CommandErrors (bad data length / bad checksum), with RX buffer flushes between attempts to clear stale partial-frame responses. Also update CommandError to decode the v1.1.0 stub's 16-bit big-endian response codes (0xC000=bad data length, 0xC100=bad checksum, etc.) and add IsRetryable() to distinguish transient serial errors from device-side failures. Signed-off-by: deadprogram <ron@hybridgroup.com>
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This PR fixes intermittent flash failures (timeouts and data corruption) when flashing ESP32 at 460800 baud.