2019-11-14 06:00 AM
Hello! I noticed a speed error on MCU L476 and L433. When setting MSI frequency to 1 MHz, the frequency is 1015.5. (Auto trimered by LSE, LSE enabled and work well) At higher frequencies, the operation is normal. What could be the reason?
2019-11-14 04:50 PM
And at lower frequencies?
Have you read out and checked RCC_CR.MSIPLLEN?
Have you checked that LSE is actually running?
JW
2019-11-14 10:29 PM
at lower frequencies below 1Mhz MSI get wrong freq, wen i set freq abowe 1 MHz MSI work well.
LSE actually running.
I see this in the care of the frequency when heating and cooling the chip. Indeed, auto-tuning works excellently. When I turn off the MSI, the frequency is very temperature dependent. I would like to work on a frequency selective and below 1 MHz with auto-tuning by MSI.
2019-11-14 11:50 PM
Set measured Error %
100000 98306 1,694
200000 196614 1,693
400000 393227 1,69325
800000 786453 1,693375
1000000 1015836 -1,5836
2000000 1998902 0,0549
4000000 3997804 0,0549
8000000 7995608 0,0549
16000000 15991217 0,05489375
24000000 23989823 0,0424041667
2019-11-15 12:07 AM
Okay, and with the MSIPLL on, the 1MHz is always off 1.5%, or does it change with temperature?
Can you please have a look at whether RCC_CR.MSIPLLEN stays on?
JW
2019-11-15 12:27 AM
1MHz is always off 1.5%, good temperature stability. When I turn off the LSE, the frequency is 998 kHz and is very temperature dependent
RCC_CR.MSIPLLEN
SET_BIT(RCC->CR, RCC_CR_MSIPLLEN) ;
2019-11-15 12:51 AM
Sounds like a hardware bug, then...
JW
@Amel NASRI , @Viktor POHORELY
2019-11-15 01:28 AM
Yes, but in erratasheet not fixed.
I would like to work at low frequencies with quartz stability. But HSE quartz consumes a lot of energy (above 1mA)... It seems that you will have to work at a frequency above 2 MHz