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MauFanGilaMedical
Associate III
February 11, 2026
Question

SD_TIMEOUT 30s

  • February 11, 2026
  • 1 reply
  • 80 views

Hello,

I'm using uSD.

I observe that in the sd_diskio.c driver SD_TIMEOUT is 30sec, is'nt very long ?

If uSD works normally is not sufficient just 1sec ?

 

Best regards. 

1 reply

Technical Moderator
February 11, 2026

Hello @MauFanGilaMedical 

Some SD cards can be significantly slower than typical cards, particularly at low bus clock speeds. In these cases, certain operations such as internal erase or program (for example erasing blocks or writing to specific internal areas) may take several hundred milliseconds and can even exceed 1 second in worst‑case conditions. For this reason, the default SD_TIMEOUT value in the ST reference driver is set quite long. It is designed to avoid false timeout errors. In a final product, this value can be reduced based on the actual SD cards used and the system constraints.

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