I want to use USB<>UART converter on CP2102 as UPDI programmer for ATmega808.
When reading the ATmega808 datasheet, I expected to check this programmer, requesting SIB of ATmega808.
As I understand, it is enough to send a BREAK (about 40ms - like two BREAKS using minimal UPDI bitrate 300bps, but without a STOP BIT in between), and then after about 4ms (not more than 13ms after BREAK) to send 0x55 0xE5 using another bitrate (9600 bps; 0x55-sync sequense, 0xE5 - SIB request) and to read the ATmega808' response.
But I only see a short pulse from the ATmega808. The time interval to the pulse after sending 0x55 0xE5 depends on the bitrate. It equals about 10*time of 1 word sending (12bits).
Is there something wrong in this sequence?
I attached the waveform:
the end of 40ms BREAK pulse - 4ms PAUSE - the sending of '0x55 0xE5': 0(start) 10101010 0(EvenParity) 11(2stopbits) 0(start) 10100111 1(EvenParity) 11(2stopbits) - 13ms - ATmega808' pulse
I downloaded Python and C projects for this theme from Github, so, I don't need the links to alien projects.