I know it is not advisable to run SoftwareSerial at above 9600bps. But due to design constraints, I have not much choice. Have someone tried if SoftwareSerial can transmit at 38400bps with a Atmega328 running a 8Mhz crystal at 3V3 supply? I don’t care about receiving. Just need to transmit properly.
Not tried, but did quite some testing on SoftSerial (mostly @16Mhz) here - SoftwareSerial magic numbers - Libraries - Arduino Forum -
What I learned from that was that softserial starts to fail seriously from 70000 Baud and up @16Mhz.
Translating this to 8Mhz indicates that 35000 baud is the upper limit for reliable transmission, so 38400 is at least in the danger zone.
However the software serial formulas allow you to adjust the baud rate a bit which can improve the transmission quality.
e.g. you can compensate for inexact timing. So maybe 38400 is not reliable, but 38100 or 38765 is.
The thread mentioned above has 8Mhz formulas too, feel free to test them.
Please let me know the results (preferably in the experimental thread)