MicroPython and SPI RAM: A Comprehensive Guide

MicroPython is a lean and efficient implementation of the Python 3 programming language that includes a small subset of the Python standard library and is optimised to run on microcontrollers and in constrained environments. SPI RAM (Serial Peripheral Interface Random Access Memory) is a type of external memory that can be connected to a microcontroller using the SPI protocol. Combining MicroPython with SPI RAM allows developers to expand the memory capabilities of their microcontroller projects, enabling them to handle larger data sets and more complex operations. In this blog post, we will explore the fundamental concepts of MicroPython and SPI RAM, discuss how to use them together, look at common practices, and share some best practices for getting the most out of this powerful combination.

Table of Contents#

  1. Fundamental Concepts
  2. Usage Methods
  3. Common Practices
  4. Best Practices
  5. Conclusion
  6. References

Fundamental Concepts#

MicroPython#

MicroPython provides a high - level programming interface for microcontrollers. It allows developers to write code in Python, which is known for its simplicity and readability. This means that developers can quickly prototype and develop applications without having to deal with the low - level details of the hardware in the same way as they would with languages like C or Assembly.

SPI RAM#

SPI RAM is a type of external memory that uses the SPI protocol for communication. It is a cost - effective way to add additional memory to a microcontroller. The SPI protocol is a synchronous serial communication protocol that uses four signals: Serial Clock (SCK), Master Out Slave In (MOSI), Master In Slave Out (MISO), and Chip Select (CS). The microcontroller can read from and write to the SPI RAM using these signals.

Usage Methods#

Hardware Connection#

First, you need to connect the SPI RAM to your microcontroller. Here is a typical connection example for an ESP32 microcontroller and an SPI RAM chip (e.g., W25Q64):

ESP32 PinSPI RAM Pin
GPIO18SCK
GPIO23MOSI
GPIO19MISO
GPIO5CS

MicroPython Code Example#

The following code shows how to initialise the SPI interface and communicate with the SPI RAM:

import machine
 
# Initialize SPI
spi = machine.SPI(2, baudrate=1000000, polarity=0, phase=0, sck=machine.Pin(18), mosi=machine.Pin(23), miso=machine.Pin(19))
cs = machine.Pin(5, machine.Pin.OUT)
 
# Function to write a byte to the SPI RAM
def write_byte(address, data):
    cs.value(0)
    spi.write(b'\x02')  # Write command
    spi.write(int.to_bytes(address, 3, 'big'))
    spi.write(int.to_bytes(data, 1, 'big'))
    cs.value(1)
 
# Function to read a byte from the SPI RAM
def read_byte(address):
    cs.value(0)
    spi.write(b'\x03')  # Read command
    spi.write(int.to_bytes(address, 3, 'big'))
    data = spi.read(1)
    cs.value(1)
    return int.from_bytes(data, 'big')
 
 
# Write a byte to address 0x00
write_byte(0x00, 0xAA)
 
# Read the byte from address 0x00
read_data = read_byte(0x00)
print("Read data:", read_data)

In this code, we first initialise the SPI interface on the ESP32. Then we define two functions: write_byte and read_byte to write and read a single byte from the SPI RAM respectively. Finally, we write a byte to address 0x00 and then read it back and print the result.

Common Practices#

Memory Management#

When using SPI RAM with MicroPython, it is important to manage the memory effectively. You can divide the SPI RAM into different regions for different purposes, such as storing data buffers, configuration information, or program code.

Error Handling#

Since the communication with the SPI RAM is based on the SPI protocol, errors can occur due to various reasons such as electrical interference or incorrect wiring. You should implement error - handling mechanisms in your code. For example, you can check the return values of the SPI read and write operations and retry the operations if an error occurs.

Best Practices#

Use Libraries#

There are some existing MicroPython libraries available for working with SPI RAM. Using these libraries can save you a lot of time and effort. For example, the spi_flash library can simplify the operations of reading and writing to the SPI RAM.

Optimise SPI Speed#

The SPI communication speed can have a significant impact on the performance of your application. You should adjust the baudrate parameter of the SPI initialisation according to the capabilities of your microcontroller and the SPI RAM chip. A higher baudrate can increase the data transfer speed, but it may also introduce more errors.

Conclusion#

MicroPython and SPI RAM together provide a powerful solution for expanding the memory capabilities of microcontroller projects. By understanding the fundamental concepts, using the correct usage methods, following common practices, and adopting best practices, developers can efficiently use SPI RAM in their MicroPython applications. With this combination, you can handle larger data sets, develop more complex algorithms, and create more advanced embedded systems.

References#

  1. MicroPython official documentation: https://docs.micropython.org/
  2. ESP32 datasheet: https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf
  3. SPI RAM chip datasheets (e.g., W25Q64 datasheet) from the respective manufacturers.
2025-10