Arduino MKR wifi 1010: spi0＋spi1

[PaulRB]

Why is the SD library slow?

I am the author of SdFat, the base library for SD. Several people have asked me why SD is so slow in Arduino 22 when you use print() for numbers. Here is the reason SD is so slow and a way to speed it up by a factor of 100. Print does character at a time writes when it formats numbers. SD has been setup to do a flush after every write. This means that println(n) will call flush six times for a four digit number, four times for the digits and two times for the new line. SD cards can only be r…