HI Alan, Yes, that is true, some are really good - SAME70 will work that way but no USB. And yes, MEMS is not there yet. In this case, my BOM was wrong - X1 DNP - so I got enough running to make progress anyhow (tested a lot of HW).
The most interesting aspect of this F103 finding for me is that the system works, and then suddenly it does not! Most likely after some burn-in on the device. I noticed this on two systems which ran overnight and then suddenly, whammo, they all failed (no NSH). Then I changed the baud rate ever so slightly and it worked again! Crazy! I change the code back to 921600, hit it with cold spray - working! Let it heat up, lock up. So yes, 50 cents and the problem is solved. Thank you! -James On Tue, Aug 23, 2022 at 5:15 PM Alan Carvalho de Assis <acas...@gmail.com> wrote: > I don't know how ST internal oscillator is implemented in silicon, but > some MCUs have good internal oscillator. > > For example the SAMD21 used on Arduino M0 board works fine with NSH > running at 115200 and it even supports USB console, but I didn't test > your freezing spray, maybe it could fail too. :-) > > This article compares crystal oscillator vs MEMS oscillator: > > > https://www.avnet.com/wps/wcm/connect/onesite/9be4733b-3e9a-4880-8887-7d19ecf34a0e/quartz-crystal-vs-mems-oscillator.pdf > > The crystal oscillators are "crystal clear winner" (pun intended). > > I agree it is better to pay some cents to include a crystal in the > board, but unfortunately the capitalism's pressure forces people to > make mistakes. > > BR, > > Alan > > On 8/23/22, James Dougherty <jafr...@gmail.com> wrote: > > Hi David, > > > > Wow. That is precisely what is wrong, you can get yourself a little TRIM > > and make one of the boards work, but > > then you would have to hand tune them +/- 1% for every baud rate and > worse, > > temperatures. So better to pay the 71 > > cents and put the 8M crystal on the board. For testing I used cold spray > > and different baud rates to see that it is much > > worse, probably more like 2% on the megabaud rates. APB1 can't go over > > 36Mhz or the backplane hangs. > > PS, the other app note is on 8Mhz HSI and link is here > > > https://www.st.com/resource/en/application_note/an2868-stm32f10xxx-internal-rc-oscillator-hsi-calibration-stmicroelectronics.pdf > > > > Anyhow, the summary is one may use the HSI for bringup and get NSH on > > /dev/ttyS0 as /dev/console but for real > > comms and especially megabaud you need external resonator or crystal and > > HSE enabled as per default in stmf103-minimum > > > > Thank you. > > -James > > > > > > > > > > On Mon, Aug 22, 2022 at 11:55 PM David Sidrane <david.sidr...@nscdg.com> > > wrote: > > > >> HSI is not a good choice if there are external interfaces. It can vary > >> too > >> much part to part and over temperature to meet the 2% across the system > >> boundary. They claim 1% @25c but that is 1/2 the budget to begin with, > >> > >> > >> > https://www.st.com/resource/en/application_note/dm00425536-how-to-optimize-stm32-mcus-internal-rc-oscillator-accuracy-stmicroelectronics.pdf > >> > >> > >> > >> > >> On Tue, Aug 23, 2022 at 2:10 AM James Dougherty <jafr...@gmail.com> > >> wrote: > >> > >> > Anyone ever use the HSI on STM32F103, how about RET6? I know the code > >> > is > >> > set up for HSE. I got it working, at least UART1. > >> > But now, the other usart devices ... Wondering if anyone has ever run > >> into > >> > UART baud rate mismatches on using HSI? I have a few > >> > radios that work great with an existing driver and a diff design, but > >> > not > >> > joy on the F103RET6. I am using internal PLL, x8 (64Mhz) > >> > and 32Mhz (APB1, APB2) if anyone has any debug pointers that would be > >> > great. Its weird, the UART1 uses APB2, and others > >> > use APB1. I know I need the external crystal but I got these boards > and > >> no > >> > clock stuffed... (sigh) > >> > > >> > thanks! > >> > -james > >> > > >> > > >
