Skip to content

Micro SD Card Reader

Secure Digital (SD) is a non-volatile memory card format for use in portable devices such as cameras, MP3 players and portable devices.

On Microcontrollers SD cards are usually access through an SPI interface although there are also devices that use I2C interfaces.

Maker Pi Pico Connections

GPIO Pin SD Mode SPI Mode
GP10 CLK SCK
GP11 CMD SDI
GP12 DAT0 SD0
GP13 DAT1 X
GP14 DAT2 X
GP15 CD/DAT3 CSn

Maker Pi Pico Example Code

Pin Definitions

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
# SD Mode Definitions
SDCARD_CLK = 10
SDCARD_CMD = 11
SDCARD_DAT0 = 12
SDCARD_DAT1 = 13
SDCARD_DAT2 = 14
SDCARD_CD_DAT3 = 15

# SPI Mode Definitions
SDCARD_SCK = 10
SDCARD_SDI = 11
SDCARD_SD0 = 12
SDCARD_X1 = 13
SDCARD_X2 = 14
SDCARD_CSn = 15

Sample Code for SPI Mode

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
import machine, os, sdcard

# Assign chip select (CS) pin (and start it high)
cs = machine.Pin(15, machine.Pin.OUT)
# Intialize SPI peripheral (start with 1 MHz)
spi = machine.SPI(1,
                  baudrate=1000000,
                  polarity=0,
                  phase=0,
                  bits=8,
                  firstbit=machine.SPI.MSB,
                  sck=machine.Pin(10),
                  mosi=machine.Pin(11),
                  miso=machine.Pin(12))
# Initialize SD card
sd = sdcard.SDCard(spi, cs)

# OR this simpler initialization code should works on Maker Pi Pico too...
#sd = sdcard.SDCard(machine.SPI(1), machine.Pin(15))

os.mount(sd, '/sd')
# check the content
os.listdir('/sd')

# try some standard file operations
file = open('/sd/test.txt', 'w')
file.write('Testing SD card on Maker Pi Pico')
file.close()
file = open('/sd/test.txt', 'r')
data = file.read()
print(data)
file.close()

Results:

1
Testing SD card on Maker Pi Pico

References

  1. MicroPython sdcard.py driver - note there is no documentation on use with the RP2040 although there is example code for the pyboard and the ESP8266
  2. MicroPython.org Documentation
  3. Raspberry Pi Pico Forum
  4. YouTube Video by Shawn Hymel
  5. Cytron Maker Pi Pico Datasheet