CHOOSE MCU
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‎2023-09-15 3:46 AM - edited ‎2023-09-15 6:26 AM
Hi.I work on BMS. I want a master-slave topology. I want to use 300 slave cards and 1 master card. This BMS is for automotive. I check ST MCU. I guess, The card should be 10-bit I2C. Because I want 300 Slave cards. So, Can you Help me this subject? Which one I will choose?
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‎2023-09-15 6:21 AM
The highlighted portion says 7-bit dual addressing mode. So dual addressing mode isn't possible for 10-bit addresses.
Standard 10 bit addressing is supported.
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‎2023-09-15 6:00 AM
Hello,
As far as I know, all the STM32 have support for 10-bits I²C addressing.
That being said, you'll have to think about what kind of interfaces you need on the STM32.
Please have a look there (section 3):
https://wiki.st.com/stm32mcu/wiki/STM32StepByStep:STM32MCU_basics
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‎2023-09-15 6:15 AM
Hi Mike,
Actually yes I saw that there is 10-bit I2C. However, when I read this sentence in the Datasheet, I got confused.
It says 7 bits for slave mode. I wasn't sure about this. So (this datasheet belongs to stm32F411) when I address it as 10 bits, I can connect 300 Slave devices together, right? Will there be a problem? And I checked the page you send.
Thanks
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‎2023-09-15 6:21 AM
The highlighted portion says 7-bit dual addressing mode. So dual addressing mode isn't possible for 10-bit addresses.
Standard 10 bit addressing is supported.
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‎2023-09-15 6:24 AM
ok thank you. I missed the dual text
Again thanks
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‎2023-09-15 6:50 AM
>> I can connect 300 Slave devices together, right ?
As long as you configure each slave to have a unique address, I don't see a limitation.
>> Will there be a problem?
Maybe you have to think about electrical problem (like capacitance). Please check I²C documentation and other online ressources.
>> This BMS is for automotive.
Please think whether you need a automotive grade MCU:
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‎2023-09-15 7:08 AM
Also note that having long I2C bus lines in an electrically noisy environment can be problematic. Cars typically use the CAN bus for communication.
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‎2023-09-18 12:32 AM
I actually checked the MCUs. In my opinion, STM32F302R6T6TR would be sufficient for the system. I2C for slave cards, ADC and GPIO for voltage circuit, and temperature sensor are adequate. I can use CAN protocol with the car communication. Is it right? Stellar MCU is very good but might be too much for me. Ä°t might be complicated.
And thank you.
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‎2023-09-18 12:35 AM
Yeah, Right. So, The car and BMS will communicate with CAN protocol.
Thank you
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‎2023-09-18 4:34 AM
To avoid having a single I2C bus with length and capacity issues (which impacts speed) you can consider using a I2C switch on the master side, such as the https://www.ti.com/product/TCA9548A or NXP one.
This also allows you to have devices with the same addresses in each branch.
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