SDIO speed with STM32F439

[formica]

Hi guys,
I'm using a custom board with an SDcard connected to a STM32F439 through SDIO port.
The SDcard is automatically recognized as mass device and everything seems to be ok but I'm noticing that writing on the SD is really slow: I have measured 10KB/sec in average on a CLASS 10 SD card.

I'm using this testing code:

Code: Select all

import utime
class sdcard_write_test:
        def __init__(self):
                self.t1 = 0
                self.t2 = 0
                self.wtime = 0
                self.char = 0x5555

        def test(self,fd):
                self.t1 = utime.ticks_ms()
                for i in range(0,50000):
                        fd.write('{:X} '.format(self.char))
                self.t2 = utime.ticks_ms()
                self.wtime = utime.ticks_diff(self.t2,self.t1)

Any idea to speedup?

Regards

[pythoncoder]

Probably a minor issue but I'd take the string formatting out of the loop:

Code: Select all

def test(self,fd):
    str = '{:X} '.format(self.char)
    self.t1 = utime.ticks_ms()
    for i in range(50000):
        fd.write(str)
    self.t2 = utime.ticks_ms()
    self.wtime = utime.ticks_diff(self.t2,self.t1)

As a general point it's probably faster to write a large buffer rather than repeatedly writing a small one, but that depends on what you're aiming to measure.