ADCS MCU - Clock circuitry design

[Aidan-Sheedy]

Motivation/Description ⛰️

The MCU needs a way of keeping track of time as the STM32 will require a clock in order to function properly.

Next Steps 🚶

• [x] Review the clock implementation on OBC V1. It may be called the "Oscillator" or something along those lines. Things to look for:
  • Frequency of clock - make sure that it is appropriate for the STM32 chip we are using
  • Complexity of design
  • Availability and cost of components
  • Design footprint/size
  • Any extraneous features we don't need
• [x] Look up clocks for circuits and how they work
• [x] Document what parts of the OBC V1 design are transferable to the ADCS MCU and what parts need redesigning. This should be done in the ADCS MCU documentation.
  • [x] All transferable design features should be documented as the current implementation in the documentation
  • [x] All non-transferable features or changes required should, along with being documented, have a ticket craeted to address the shortcomings.
• [ ] Create a circuit diagram for the ADCS MCU clock. This should be stored in the ADCS Teams and the ADCS GitHub.
• [ ] Run ORCad testing on the MCU Clock circuit to validate that it is working correctly

Supporting Material and Resources 📖

• OBC V1 Documentation
• OBC STM32 PCB Design
• ADCS MCU Documentation

Definition of Done 💯

This task is done when:

• The OBC V1 OS storage design has been transferred to the ADCS MCU
  • All transferable design features have documented
  • Missing/non-transferable features have a new ticket
• A circuit diagram of the OS storage has been created in the GitHub and the ADCS Teams channel. This is a working document, and is not expected to be complete.
• Circuit has been modelled and validated

Tags

tag people that should know about this issue

cc: @SeanTedesco @emmapaczkowski @Aidan-Sheedy @jillianmalherbe

[HarrisonMKG]

Stm32 chip have an internal clock within them to help keep track of timing: In addition, I don't think a RTC would need it's frequency lined up with the stm32 as long as it can keep accurate data. It will share a clock line for data transmission so it won't really matter in that sense and clock events will most likely be handled through software interrupts at specified intervals so I don't see why it wouldn't be compatible regardless of frequency.

[Aidan-Sheedy]

Thanks @HarrisonMKG, this is all good info. We're hoping to have a meeting with @SeanTedesco, ADCS and OBC members at some point this week or next to go over all of this, if you have some background with STM32 it would be great if you could join. (Also saw your comments on the other issues, thanks!)

[HarrisonMKG]

No worries, do you know the time and date of the meeting?

[Aidan-Sheedy]

STM32 forum on external clocks: https://community.st.com/s/article/how-to-use-stm32cubemX-to-configure-high-speed-external-oscillator-and-low-speed-external-oscillator

OBC Testing documents https://queensuca.sharepoint.com/:w:/r/teams/GROUP-QSET/Shared%20Documents/Satellite-OBC/OBC%202021-2022/Acceptance%20Test%20Plan.docx?d=wb273a5952e854b8dab4e8bdeb1e7673b&csf=1&web=1

[HarrisonMKG]

https://techoverflow.net/2021/07/26/beware-of-the-stm32-lsi-its-tolerance-is-up-to-%C2%B147/ If you need stuff to be exact (hard-timing) dont use the stm32 rtc, if it can be lose, use the stm32 IMO

[HarrisonMKG]

In addition, from my understanding the RTC in the STM32 has it's own backup battery so our previous concerns of it killing the clock when off shouldn't be an issue.