How does the noise error detection of a UART of the STM32F4 series work?

[Rookie38]

Hello Community,

in my application data is transferred between two MCUs using a UART. One of these MCUs is a STM32F429. It often detects frame and noise errors. I am aware of how a frame error is detected, but I can't find any information in the Reference Manual, the UART Application Notes nor the presentation files about what condition must exist so that the HAL Error Code HAL_UART_ERROR_NE is generated.

Does UART periodically scan between communications to detect bit-variations or how exactly does this work? In which document can I find the information? Thanks =)

[Bob S]

STM32F427 Reference Manual (RM0090 rev 18), figure 302 and table 133. There are also references to noise detection in the sections on detecting start bits. Note that the text refers to the noise flag as "NE" whereas the register description refers to it as NF.

[Rookie38]

Thanks Bob, how could I have missed that -.-

I have copied in the respective illustrations so that they can be found more quickly.

Fig 302 For Oversampling by 8

Fig 301 for Oversampling by 16

and Table 133 Noise detection from sampled data

[Bob S]

Yeah, in the G4xx ref man they give noise detection its own section so it is listed in the table of contents and the bookmarks in the PDF. The F4xx ref man just kinda throws it in there and is easy to skim past.