External crystal for USB needed?
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‎2015-09-28 7:37 PM
Is the STM32 series capable of handling low speed USB without external crystal?
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‎2015-09-28 8:41 PM
Which STM32 specifically? Most of them need a crystal to get remotely close to the required accuracy/stability needed for USB.
Some of the newer offerings have a trimmed HSI/MSI capable of generating a suitable 48 MHz reference, you should review the check-box items in the assorted press-releases and product pages.Up vote any posts that you find helpful, it shows what's working..
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‎2015-09-28 10:53 PM
Thank you for quick reply. Yes, now I see that ST does indeed explicitely feature some of the MCUs as working ''crystalless''. Good. Best regards
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‎2015-09-28 11:07 PM
One additional question. I'm planning to use it for a keyboard controller. Since STM32 MCUs come with bootloader, I don't really need a programmer, to get my firmware on it, right?
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‎2015-09-28 11:11 PM
Most have a USB DFU programming scheme, though if you want any chance of developing and debugging on the platform you really need some form of SWD/JTAG pod.
Up vote any posts that you find helpful, it shows what's working..
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‎2015-09-28 11:26 PM
I see. So it's better to include a SWD socket into the design, for whatnot may happen. Good. Thanks you, clive1
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‎2015-09-28 11:40 PM
You can do it as test points, edge castellations, or whatever floats your boat. Systems without this connectivity in some form are real hard to trouble-shoot. I'd recommend SWDIO, SWCLK, SWO, NRST, GND as a minimum, and ideally also USART1_TX and USART1_RX (or equivalent as called out in the System Loader (ROM) specs)
If you have space, using standardized connections will also save to lot of time and messing around.Up vote any posts that you find helpful, it shows what's working..
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