Serial baud rate seems incorrect on internal 20MHz

MCUdude / MegaCoreX

An Arduino hardware package for ATmega4809, ATmega4808, ATmega3209, ATmega3208, ATmega1609, ATmega1608, ATmega809 and ATmega808

GNU Lesser General Public License v2.1

242 stars 47 forks source link

Serial baud rate seems incorrect on internal 20MHz #59

Closed tgtakaoka closed 4 years ago

tgtakaoka commented 4 years ago

As long as I tried with

the latest MegaCoreX on github repo
ATmega4809-p (DIP40)
Internal 20MHz
40/48 pin standard
Optiboot (UART1 default pins)
Examples > 04.Communication > ASCIITable (with modification with #define Serial Serial1)

Not only default 9,600bps of ASCIITable but also other bps, such as 115,200bps, produces garbage on Serial Monitor.

Other clocks, Internal 16MHz to 1MHz with any baud rate work fine.

I hope this is a bug and will be fixed soon.

Thanks, Tadashi.

MCUdude commented 4 years ago

Thanks for reporting! I'm sure there's a bug in there somewhere, but unfortunately, I don't have much time to investigate this at the moment. Feel free do dive in if you like!

MCUdude commented 4 years ago

I tested this on actual hardware recently, and it worked just fine at 20 MHz. It may be that your particular chip has an oscillator that's a little out of tune.

tgtakaoka commented 4 years ago

Hi, dude/, thank you for the confirmation. I too confirmed that the latest tip-of-toe MegaCoreX + optiboot works fine with 20MHz internal clock of ATmega4809P. The issue was may be due to my serial host machine (Chromebook + crouton).

So let me close this as not-reproducible.