STM32L0 board design

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geologic
Posts: 12
Joined: Thu Dec 15, 2022 10:12 am
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STM32L0 board design

Post by geologic »

Hi all

I'm a experienced arduino maker trying to enter the STM32 world.
I made a prototype with a STM32F103 bluepill and a Lora SX1276 module and now i would like to design a custom board. My requisites are:

- battery powered, most of the time sleeping
- wake each hour to send data from sensors (RTC support)
- USB support to upload code/debug with Arduino IDE

My questions are:

1) I choosed STM32L0x2 family for their low power and USB support, it that ok?
2) I saw some designs with one 32kHz cristal, others with both 32kHz and 8MHz. I need some compromise between speed and low power, and i read somewere Lora needs some fast and precise clock, so do i need both cristals? Just one? None?
3) to use RTC to wake from sleep each hour do i need a CR2032 for power backup? Anything else?
4) Bluepill has BOOT0 and BOOT1 even i just used BOOT0 once to upload bootloader (so i can use USB to upload code). STM32L0X2 does not have BOOT1 pin, is it a problem?
5) Any other major concern?

Thanks
GonzoG
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Location: Prudnik, Poland

Re: STM32L0 board design

Post by GonzoG »

ad 1) It is, but having USB doesn't mean that MCU has DFU bootloader (USB program flashing). And there is no mention about it in some L0x2 datasheets so depending on what MCU you'll choose, you might need to build software bootloader (like HID bootloader).
DFU bootloader usually needs manual board reset.

As to debugger in Arduino IDE 2.0, I think that ST-Link is needed for this and there is no official support for debugging in STM core.

ad 2) 32kHz crystal is for built-in RTC and sleep modes in which internal oscillator is powered down. But if you need precise RTC you'll be better with external precise RTC chip (like DS3231).
You can use external high speed crystal (they are usually more precise then built-in oscillators) or you can design board without one. But for some low power modes internal oscillators might be powered down.

ad 3) You need any power source. Backup battery is needed only as a backup in case there is no power to MCU. It's to power RTC and backup registers.

ad 4) This we can't tell you. It's your design and you should know what features you need.
There is document about bootloader selection: https://www.st.com/resource/en/applicat ... ronics.pdf
geologic
Posts: 12
Joined: Thu Dec 15, 2022 10:12 am
Answers: 1

Re: STM32L0 board design

Post by geologic »

Thanks GonzoG for your reply.

Question 1:
Damn... you're right, i'll have to check it better for USB DFU bootloader capabilities. Or stick to upload by serial, that will always work, right?

Question 2:
Ok, so i'll include both crystals on my design and populate as needed. With custom Arduino boards is simple to select internal/external crystal and the Mhz speed, with STM32duino i have to choose a board with exacly the same configuration of my custom board, right? I read about making variants, but it involves using STM32CubeMX which looks overwhelming for me at this point...
Leonardoms
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Joined: Tue Jan 17, 2023 2:28 pm

Re: STM32L0 board design

Post by Leonardoms »

Hello to All. My companys R&D team is about to release to market these STM32/LoRa SIP module. I have around 20 EVB samples I can give away. Anyone interrested, please contact me.

Best regards
Attachments
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Pic1
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Pic2
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SIPLORA2.jpg (79.4 KiB) Viewed 3802 times
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fpiSTM
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Re: STM32L0 board design

Post by fpiSTM »

Leonardoms wrote: Tue Jan 17, 2023 3:04 pm Hello to All. My companys R&D team is about to release to market these STM32/LoRa SIP module. I have around 20 EVB samples I can give away. Anyone interrested, please contact me.

Best regards
Thanks for sharing but what is the link with the initial topic? You should create new topic.
Leonardoms
Posts: 2
Joined: Tue Jan 17, 2023 2:28 pm

Re: STM32L0 board design

Post by Leonardoms »

Hello. I'll create a New topic. Thanks you!
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