Bluepill, PB10 and PB11 pulling down the signal while using as input

Please do not post requests
Post Reply
raufjay
Posts: 4
Joined: Wed Feb 03, 2016 3:31 am

Bluepill, PB10 and PB11 pulling down the signal while using as input

Post by raufjay » Wed Feb 14, 2018 4:22 am

Hello,
I have a strange issue with STM32F103 blue pill board.
I am using PB10 as input. When external device try to pull high the PB10 line, it hardly goes to 1Volt. If I disconnect the PB10 and uses PA11, the signal stays at 3volts.
I tried PB11 instead with the same result.
I tried using pinMode(PB10, INPUT_PULLUP) and tried with 10K external pullup resistor as well, with the same result.

Any idea?

Thanks,

Raufjay

stevestrong
Posts: 2059
Joined: Mon Oct 19, 2015 12:06 am
Location: Munich, Germany
Contact:

Re: Bluepill, PB10 and PB11 pulling down the signal while using as input

Post by stevestrong » Wed Feb 14, 2018 8:35 am

Can you post a simple sketch which reproduces the problem?

User avatar
RogerClark
Posts: 7683
Joined: Mon Apr 27, 2015 10:36 am
Location: Melbourne, Australia
Contact:

Re: Bluepill, PB10 and PB11 pulling down the signal while using as input

Post by RogerClark » Wed Feb 14, 2018 10:10 am

Not sure if this is why, but PB10 is USART3 TX

Page 30 of

http://www.st.com/content/ccc/resource/ ... 161566.pdf

But this is not available on the Blue Pill

What board did you select ?

stevestrong
Posts: 2059
Joined: Mon Oct 19, 2015 12:06 am
Location: Munich, Germany
Contact:

Re: Bluepill, PB10 and PB11 pulling down the signal while using as input

Post by stevestrong » Wed Feb 14, 2018 10:55 am

RogerClark wrote:
Wed Feb 14, 2018 10:10 am
PB10 is USART3 TX
Page 30 of
http://www.st.com/content/ccc/resource/ ... 161566.pdf
But this is not available on the Blue Pill
Same document, page 13 says that medium density devices (20k RAM, 64kB FLASH == blue pill) have 3 x USARTs.
So Serial3 should be available for blue pill on PB10/11, even if is LQFP64.

User avatar
ahull
Posts: 1727
Joined: Mon Apr 27, 2015 11:04 pm
Location: Sunny Scotland
Contact:

Re: Bluepill, PB10 and PB11 pulling down the signal while using as input

Post by ahull » Wed Feb 14, 2018 5:06 pm

Image

On the right Roger, beside the yellow jumpers :P
(Its usually me who is over thinking the problem ;) )
- Andy Hull -

raufjay
Posts: 4
Joined: Wed Feb 03, 2016 3:31 am

Re: Bluepill, PB10 and PB11 pulling down the signal while using as input

Post by raufjay » Wed Feb 14, 2018 8:59 pm

I tried using PB10 as output and saw on the scope. It gives study 3v output. But as input it pulls down the external signal to near 1V. PB11 is the same. Yes apparently it may have something to do with USART3 but what if we use USART2 pins (PA2 and PA3) as input? does they behave the same? I haven't test them yet.
Will test them tonight.
Thank you
Rauf

stevestrong
Posts: 2059
Joined: Mon Oct 19, 2015 12:06 am
Location: Munich, Germany
Contact:

Re: Bluepill, PB10 and PB11 pulling down the signal while using as input

Post by stevestrong » Wed Feb 14, 2018 9:27 pm

I insist to get a simple sketch which can be used to reproduce the problem.
For example, put pc13 to toggle and put pb10 to input the signal from pc13 and monitor it on serial usb.
It must work.
I think it will turn out that the sw did something wrong.

User avatar
RogerClark
Posts: 7683
Joined: Mon Apr 27, 2015 10:36 am
Location: Melbourne, Australia
Contact:

Re: Bluepill, PB10 and PB11 pulling down the signal while using as input

Post by RogerClark » Wed Feb 14, 2018 9:46 pm

Steve

If they selected the wrong board e.g. STM32F103V, It would compile and be possible to upload a binary
But I don’t know what the result would be..

The pin is also defined as I2C2, SCL2, so potentially there could be an issue with the Wire config.

However it’s odd that no one else has noticed this, and perhaps it’s just a faulty chip

Post Reply