Is interbal RC Osc accurate enough for serial UART TS232 for STM32F103RB?

[john1389]

Posted on July 22, 2016 at 22:31

Is it true that 2 to 3% accuracy is required? 

Nucleo F103 has no crystal. Nucleo F401 has 32kHz crystal

[waclawek.jan]

Posted on July 22, 2016 at 23:12

> Is it true that 2 to 3% accuracy is required? 

Yes.

JW

[Tesla DeLorean]

Posted on July 23, 2016 at 01:14

Both Nucleo boards can take an 8 MHz clock source from the ST-LINK chip which does have an HSE clock.

USARTs can tolerate a fair amount of clock error.

The LSI is not only likely to be off in frequency, but it also changes (poor stability). Can't say I've spent a lot of time looking at the HSI, but have got some boards wired to a GPS 1PPS source so could probably evaluate it.