Hi All,
I want to design USB schematic for STM32F105VCT6. I read Introduction to USB hardware and PCB guidelines using STM32 MCUs(AN4879) and it said that STM32F105/STM32F107 has Pull-up resistor on USB_DP line.
Question 1
Can I design USB schematic with no Pull-up resistor on USB_DP? And no need any config about embedded Pull-up resistor in software?
Question 2
Should I put some resistor between USB connector and STM32F105 on both USB D+,D- ? If yes, what value should add.
This is example schematic from stm32 bluepill. I saw there are resistor between USB connector and STM32F103
Thank you for your answer
1 ACCEPTED SOLUTION
Accepted Solutions
Dear @WPong.1 ,
Here you go :
https://www.st.com/resource/en/datasheet/stm32f107vc.pdf#page95
No need for Serial resistance neither the pull-up . You need to connect D-, D+ and VBus to the connector , in case of your device is bus powered that means all power from VBus : 5volts from Host , in case of Host follow the recommendation as well.
Hope it helps ,
STOne-32
Hi,
see ds:
-> no need for any external resistor .
(and dont ever use pullup to +5V ! Thats just wrong. USB has 3v3 signal levels...! )
+ only (old) F103 needs 1k5 pullup to 3v3 .
Dear @WPong.1 ,
Here you go :
https://www.st.com/resource/en/datasheet/stm32f107vc.pdf#page95
No need for Serial resistance neither the pull-up . You need to connect D-, D+ and VBus to the connector , in case of your device is bus powered that means all power from VBus : 5volts from Host , in case of Host follow the recommendation as well.
Hope it helps ,
STOne-32
Thank you for your answer. I found that in STM32CubeMX, I did not select Activate VBUS so it made embedded pull-up resistor not pull to signal full-speed peripheral connections then PC and STM32 device are not communicate together(No COM Port available [I use USB CDC class]).
After solve the problem I have read reference manual again and found that "DP/DM integrated pull-up and pull-down resistors controlled by the OTG_FS core depending on the current role of the device. As a peripheral, it enables the DP pull-up resistor to signal full-speed peripheral connections as soon as VBUS is sensed to be at a valid level (B-session valid)."
that is reason why if I select Activate VBUS in STM32CubeMX, USB CDC work properly.
Thank for your help again.
