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HardFOC driver

AT25040 Driver

A header-only C++17 driver for the Microchip AT25040B serial EEPROM (also AT25010B and AT25020B). It detects the chip safely, reads and writes it in pages and reports every result as a status, on any MCU with SPI.

Quickstart API guide Source on GitHub

The driver has no platform code. You give it a small class with one method that runs an SPI transaction; it does the rest: the instruction set, the ninth address bit, bounds and page checks, and a probe that tells a missing chip from a present one.

4-Kbit SPI serial EEPROM AT25040B Microchip (Atmel)
Memory
512 x 8 bits (AT25040B); 128 x 8 (AT25010B), 256 x 8 (AT25020B); 8-byte pages
Interface
SPI mode 0 or 3, MSB first; 20 MHz at 4.5 V to 5.5 V, 10 MHz at 2.5 V, 5 MHz at 1.8 V
Supply
1.8 V to 5.5 V; 3.5 µA maximum standby at 5 V
Writes
Self-timed, 5 ms maximum per page; 1,000,000 cycles, 100-year retention
Protection
WP pin, write-enable latch, block protection of the top ¼, top ½ or whole array
Package
8-lead SOIC, TSSOP, UDFN, XDFN, 8-ball VFBGA; -40 °C to +85 °C

Product page and datasheet

What you get

  • One object per chip. at25040::Device<YourSpi> with Probe(), Read(), Write(), WritePage(), WaitReady(), block protection and the write-enable latch. See API guide.
  • Safe detection. Probe() reads the status register twice and rejects a floating bus (0xFF) and a bus that echoes the command back. See Hardware.
  • The ninth address bit handled. Addresses 0x100 to 0x1FF put A8 into the opcode for you. See Protocol.
  • Checks before the bus. A bad pointer, a zero length, a range past the array or a write that crosses a page returns Status::Arg without touching SPI.
  • Zero-overhead portability. The port is a CRTP class: no virtual calls, no heap, no exceptions, no RTOS. See Porting.
  • Tested without hardware. Host unit tests run the driver against a model of the chip. See Testing and CI.

Where to go next

  • Quickstart

    Wire the chip, write the port, store and read back four bytes.

  • Hardware

    Pins, bus settings, timing, power and write protection.

  • Architecture

    The three layers and what each one owns.

  • API guide

    Probe, read, write, wait and handle errors, task by task.

  • Porting

    Implement the one-method SPI interface for your MCU.

  • API reference

    Every class and constant, generated from the headers.