Hi,
My conclusion is clear that it is not a matter of physics (electrical) but of timing constraints.
If you can see the PROMPT1 / 2 and the download either doesn't finish or you get a NACK, then yes, it's probably timing. If you don't see PROMPT1/2 then it's electrical.
The bootloader serial routing is stupid as hell ... basically you have : (from memory but the idea is there)
uint8_t read_char() { for (int i=0; i<4096; i++) if (is_char_ready()) return get_char_from_buffer(); return 0; }
So basically if it doesn't get a char in time, it return 0x00 and the caller has no idea if the 0 is a received char or a timeout ...
- after loading the firmware none of the cables ever made any problems
(thanks to Harald's HDLC layer:-)
It's both the HDLC and also the fact the uart is handled _way_ better in our code than the
- Prolific is noisy, that means if the plug is not connected to the phone you will see
endless random characters received my osmocom
Probably depends on the cable ... some prolific could have a pullup/down.
Cheers,
Sylvain