Posted on June 03, 2017 at 18:53
hello,
I would like to have some clarification about the USB circuit needed for the stm32f103 (and similar), I am making a simple development board just to start learning this MCU
This is taked from the maple mini
https://github.com/leaflabs/maplemini
also the rev5/6 and other boards present a similar circuit. DISC cames from PB9my guess is that the 2 transistors stay there to power the R10 to pull up DP when the board is connected to USB otherwise, when powered from other sources, DP and DM could be used as normal GPIO (PA12 and 11). Am i wrong?
about the two cap for the usb line (c10 and 11) and the pull up for DP (R10) i saw them only in a few boards, could i live without them or is it suggested to add all?
In other schematics (example:
http://eleccelerator.com/stm32f4stamp-breakout-board/
) i found that sometimes the USB ID is wired to PA10, what does it mean?Thanks for reading
#basic-circuit #usb #analog
Posted on June 12, 2017 at 13:56 
Hi
Gibiino.Vincenzo
,- On the STM32F103 devices, It's mandatory to pull up the the USB_DP pin with a 1.5KΩ resistor to a 3.0 to 3.6 voltage range.This is already indicated on the datasheet as a note below table ''USB DC electrical characteristics'' (USB characteritics section):
- The STM32F103 MCUs support a USB2.0 FS device interface. While, the STM32F4 devices support a USB 2.0 OTG FS.Here, when the dual role device mode is used, the host or peripheral role (the default role) is assumed depending on the ID input pin. For this reason, the ID pin of the connector should be wired to PA10 (OTG_FS_ID).Please refer to section ''ID line detection'' on the reference manual (for devices where OTG is supported) for more details.
Khouloud.
