Created attachment 731 [details] example capture Attached is a capture of a UART transmission which used a falling edge trigger on the D0 channel. PulseView started recording samples when the trigger condition occurred, which would represent the UART start bit. However, if you apply the UART decoder to this channel, the start bit is not properly recognized, which leads to incorrect decoding of the first octet. This is because the decoder looks for the falling edge, but the first recorded sample is already low voltage. It would be useful if I could specify how many samples to capture prior to the trigger.
There is an option to set the initial value of a PD. It can be enabled by Settings->Decoders->Allow configuration of initial state After enabling the option you can specify the initial value in the PD settings
Known and valid behaviour. The capture does not contain the start condition of the UART frame, which is why the decoder kicks in late. There are the options to properly setup the acquisition (capture ratio) or to use the workaround of specifying initial levels (which are motivated by this very setup as described above). So there is no issue. Am closing the report.