Dear Tech Support,
I am curious about behavior when the ISP autobaud synchronization fails – currently this only happens when I go outside the expected limits e.g. when I drive in the sync character immediately after resetting into ISP mode. The autobaud procedure then gets some interesting results. It functions as expected when I properly wait a few ms after reset before trying to synchronize.
The manual seems to suggest that responding with “Synchronized\r\n” should trigger a sync failure and allow for resynching, but this doesn’t appear to happen automatically. (A quick attempt at sending a Synchronized response that doesn’t fit the autobaud expectation nor a subsequent ‘?’ doesn’t seem to trigger a correct, or even attempt at a subsequent, autobaud calculation. How do I force a resynch to handle (unlikely?) potential autobaud failures?
Secondly, it doesn’t appear (small sample size) to matter if my autobaud trigger (‘?’) is also ‘\r’ ’\n’ terminated. The manual says extra termination characters are ignored, so I take it that it’s not a problem, but wanted confirmation.
Finally, is there a way to force a bypass of the USB ISP mode and go directly to UART ISP despite VBUS assertion by a USB connection? We can hold off on the reset into ISP mode if USB is connected, but if there was a secret way to avoid that check, I’d be happy to just override the default behavior.