Raspberry Pi Pico - Read Config from SD Card
This tutorial explains how to read configuration settings from a file stored on a Micro SD Card using the Raspberry Pi Pico with MicroPython. You will learn to:
- Prepare a config.txt file containing key-value pairs on the Micro SD Card.
- Read a setting from the config file and store it in an int variable.
- Read a setting from the config file and store it in a float variable.
- Read a setting from the config file and store it in a String variable.
Hardware Preparation
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| 1 | × | DIYables Sensor Kit (30 sensors/displays) | |
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
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Additionally, some of these links are for products from our own brand, DIYables .
Overview of Micro SD Card Module
To learn about the Micro SD Card Module — including pin descriptions, wiring, and example code — refer to the Raspberry Pi Pico - Micro SD Card tutorial.
How It Works
The config file on the Micro SD Card uses a simple text-based format:
- One key-value pair per line, with each line separated by a newline character.
- Inside each line, the key and its value are split by the = character.
The MicroPython code looks up a specific key in the file, extracts its value, and assigns it to a variable. Depending on the key, the value is converted to int, float, or String.
Wiring Diagram
This image is created using Fritzing. Click to enlarge image
The wiring table below shows how to connect the Micro SD Card Module to the Raspberry Pi Pico:
| Micro SD Card Module | Raspberry Pi Pico |
|---|---|
| VCC | VBUS (5V) |
| GND | GND |
| MISO | GP4 |
| MOSI | GP3 |
| SCK | GP2 |
| CS | GP5 |
※ NOTE THAT:
When using a shield that already includes a Micro SD Card slot (for example, an Ethernet shield), no additional SD Card Module is required — just slide the card straight into the shield's built-in slot.
How to Load Config Settings into Variables
- Open Notepad or Notepad++ and create a new file named config.txt. Add the key-value pairs shown below:
myString_1=Hello
myString_2=newbiely.com
myInt_1=2
myInt_2=-105
myFloat_1=0.74
myFloat_2=-46.08
- Plug the Micro SD Card into your computer with a USB 3.0 SD Card Reader.
- Confirm the card is formatted as FAT16 or FAT32 (search online for formatting instructions if necessary).
- Copy the config.txt file to the root folder of the Micro SD Card.
- Safely eject the Micro SD Card from the computer.
- Attach the Micro SD Card to the Raspberry Pi Pico through the SD Card Module, following the wiring diagram.
- Install the sdcard library on the Raspberry Pi Pico via Thonny IDE:
- Go to Tools Manage packages in Thonny IDE.
- Type sdcard in the search box and install the micropython-sdcard package.
- Paste the following MicroPython code into Thonny's editor.
- Click Run to execute the code on the Raspberry Pi Pico.
- Check the Shell for the output:
- The parsed values in the Shell match exactly with the entries saved in the config file on the Micro SD Card.
"""
This Raspberry Pi Pico MicroPython code was developed by newbiely.com
This Raspberry Pi Pico code is made available for public use without any restriction
For comprehensive instructions and wiring diagrams, please visit:
https://newbiely.com/tutorials/raspberry-pico/raspberry-pi-pico-read-config-from-sd-card
"""
import machine
import os
import sdcard
# Define SPI pins for the Micro SD Card module
SPI_SCK_PIN = 2 # The Raspberry Pi Pico pin GP2 connected to SCK
SPI_MOSI_PIN = 3 # The Raspberry Pi Pico pin GP3 connected to MOSI
SPI_MISO_PIN = 4 # The Raspberry Pi Pico pin GP4 connected to MISO
SPI_CS_PIN = 5 # The Raspberry Pi Pico pin GP5 connected to SS (CS)
FILE_NAME = "/sd/config.txt"
# Variables
my_int_1 = 0
my_int_2 = 0
my_float_1 = 0.0
my_float_2 = 0.0
my_string_1 = ""
my_string_2 = ""
def sd_find_key(key):
"""Search for a key in the config file and return its value as a string."""
try:
f = open(FILE_NAME, "r")
for line in f:
line = line.strip()
if "=" in line:
k, v = line.split("=", 1)
if k == key:
f.close()
return v
f.close()
except Exception as e:
print("SD Card: Issue encountered while attempting to open the file", FILE_NAME, e)
return None
def sd_find_int(key):
"""Read a key from config file and return as int.
"""
value = sd_find_key(key)
if value is not None:
return int(value)
return 0
def sd_find_float(key):
"""Read a key from config file and return as float."""
value = sd_find_key(key)
if value is not None:
return float(value)
return 0.0
def sd_find_string(key):
"""Read a key from config file and return as string.
"""
value = sd_find_key(key)
if value is not None:
return value
return ""
# Initialize SD card using SoftSPI and sdcard driver
spi = machine.SoftSPI(baudrate=1000000, polarity=0, phase=0,
sck=machine.Pin(SPI_SCK_PIN),
mosi=machine.Pin(SPI_MOSI_PIN),
miso=machine.Pin(SPI_MISO_PIN))
cs = machine.Pin(SPI_CS_PIN, machine.Pin.OUT)
try:
sd = sdcard.SDCard(spi, cs)
os.mount(sd, "/sd")
print("SD Card initialized.")
except Exception as e:
print("SD CARD FAILED, OR NOT PRESENT!", e)
raise SystemExit
my_int_1 = sd_find_int("myInt_1")
my_int_2 = sd_find_int("myInt_2")
my_float_1 = sd_find_float("myFloat_1")
my_float_2 = sd_find_float("myFloat_2")
my_string_1 = sd_find_string("myString_1")
my_string_2 = sd_find_string("myString_2")
print("myInt_1 =", my_int_1)
print("myInt_2 =", my_int_2)
print("myFloat_1 =", my_float_1)
print("myFloat_2 =", my_float_2)
print("myString_1 =", my_string_1)
print("myString_2 =", my_string_2)
os.umount("/sd")
Shell x
>>> %Run -c $EDITOR_CONTENT
MPY: soft reboot
SD Card initialized.
myInt_1 = 2
myInt_2 = -105
myFloat_1 = 0.74
myFloat_2 = -46.08
myString_1 = Hello
myString_2 = newbiely.com
MicroPython (Raspberry Pi Pico) • Board CDC @ COM29 ≡
You can extend the code by adding more key-value pairs to suit your project.
※ NOTE THAT:
The lookup order of entries in the config file does not matter. The code scans from top to bottom until a matching key is found.