Hacker News Reader

> Note that this can only be done because both systems are 3.3v

Glares at system that ran RS232 levels (-12 & +12) into 5V Atmel MCU 24/7 for a couple years successfully

Wait what? Uart is active low. So it’s not to hard to bump the 12V down to 5V, but what happened with the -12V?

Just saying a 5V device had no problem interpreting -12 as 0 and +12 as 1 (wayyyy out of specs). And the serial port accepted 5 as good as +12 and 0V as -12V. No level shifting.

Did require inverting in code since RS232 uses -12V as logic 1 and +12 as 0.

Reply on news.ycombinator.com