Fastest sd clockrate possible with sandisk ultra 32gb card

software/src/hwconfig_Rev1.py

@@ -9,7 +9,7 @@ SD_DI = Pin.board.GP3
 SD_DO = Pin.board.GP4
 SD_SCK = Pin.board.GP2
 SD_CS = Pin.board.GP5
-SD_CLOCKRATE = 25000000
+SD_CLOCKRATE = 16000000
 
 # MAX98357
 I2S_LRCLK = Pin.board.GP6
@@ -49,8 +49,8 @@ def board_init():
 
     # SD_DO / MISO input doesn't need any special configuration
     # Set 8 mA drive strength for SCK and MOSI
-    machine.mem32[0x4001c004 + 2*4] = 0x60  # SCK
-    machine.mem32[0x4001c004 + 3*4] = 0x60  # MOSI
+    machine.mem32[0x4001c004 + 2*4] = 0x71  # SCK
+    machine.mem32[0x4001c004 + 3*4] = 0x71  # MOSI
     # SD_CS doesn't need any special configuration
 
     # Permanently enable amplifier