how to use sdFat library on M5Stack in short.
I would like to use the sdFat library on the M5Stack because I need the long file names.
There were some unexpected issues (for me) that I want to document here.
The original SD library is integrated in the M5Stack library. The sdFat library can be used in parallel if a few settings are made correctly.
There are 3 files in the src folder, with Arduino IDE they have to be renamed from *.cpp to *.ino.
-
sdFAT_M5Stack_Test.cpp
This is the first attempt to use the lib with M5Stack. It shows the files and folders on the sd-card -
sdFAT_bench.cpp
This is a benchmark with the new library. -
SD_bench.cpp
This is a benchmark with the original library.
-
the SPI bus on M5Stack is shared with the TFT
https://docs.m5stack.com/#/en/core/gray -
the TFCARD_CS_PIN is defined in M5Stack Config.h (Pin 4)
https://github.com/m5stack/M5Stack/blob/6cd8ce15e723c2043a3c01763320413ebff300d5/src/utility/Config.h#L14 -
the SPI bus read frequency for the TFT is 16 MHz
https://github.com/m5stack/M5Stack/blob/6cd8ce15e723c2043a3c01763320413ebff300d5/src/utility/In_eSPI_Setup.h#L266 -
max speed of SPI bus for SD card is 40 MHz
https://github.com/m5stack/M5Stack/blob/6cd8ce15e723c2043a3c01763320413ebff300d5/src/M5Stack.cpp#L27 -
the max speed of SPI with sdFat library is 25 MHz, higher speed will cause errors
I don't know, why there are these speed issues, but the sdFat library is at 16 MHz slightly faster then the original one.
The original code of the benchmark is located at: https://codebender.cc/example/SdFat/benchSD#benchSD.ino
// in main file define the max SPI speed
#define SPI_SPEED SD_SCK_MHZ(25) // MHz: OK 4, 10, 20, 25 too much: 29, 30, 40,
#define SD_CONFIG SdSpiConfig(TFCARD_CS_PIN, SHARED_SPI, SPI_SPEED) // TFCARD_CS_PIN is defined in M5Stack Config.h (Pin 4)
if (!sd.begin(SD_CONFIG)) {}// in file SdFat\src\SdFatConfig.h at Line 100:
#define ENABLE_DEDICATED_SPI 0sdFat benchmark on M5Stack
##########################
Type any character to start
File size 5MB
Buffer size 100 bytes
Starting write test. Please wait up to a minute
Write 77.38 KB/sec
Maximum latency: 146413 usec, Minimum Latency: 1 usec, Avg Latency: 1291 usec
Starting read test. Please wait up to a minute
Read 296.52 KB/sec
Maximum latency: 10455 usec, Minimum Latency: 1 usec, Avg Latency: 336 usec
Done
SD benchmark on M5Stack
#######################
Type any character to start
File size 5MB
Buffer size 100 bytes
Starting write test. Please wait up to a minute
Write 68.35 KB/sec
Maximum latency: 191672 usec, Minimum Latency: 12 usec, Avg Latency: 1454 usec
Starting read test. Please wait up to a minute
Read 258.91 KB/sec
Maximum latency: 3927 usec, Minimum Latency: 9 usec, Avg Latency: 382 usec
Done- thanks to the makers of M5Stack, I like to have a nice all in one case in my projects :-)
- thanks to Bill Greiman for the sdFat library https://github.com/greiman/SdFat