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Added 24LC32 EEPROM I2C example
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‎README.md‎

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[ht16k33_i2c](i2c/ht16k33_i2c) | Drive a 4 digit 14 segment LED with an HT16K33.
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[slave_mem_i2c](i2c/slave_mem_i2c) | i2c slave example where the slave implements a 256 byte memory.
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[slave_mem_i2c_burst](i2c/slave_mem_i2c) | i2c slave example where the slave implements a 256 byte memory. This version inefficiently writes each byte in a separate call to demonstrate read and write burst mode.
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[24lc32_i2c](i2c/24lc32_i2c) | Read and write data to 24LC32 EEPROM via I2C.
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### Interpolator
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‎i2c/24lc32_i2c/24lc32_i2c.fzz‎

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‎i2c/24lc32_i2c/24lc32_i2c.png‎

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‎i2c/24lc32_i2c/24lc32_i2c_lib.c‎

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#include <stdio.h>
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#include "pico/stdlib.h"
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#include "hardware/i2c.h"
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// This is the max number of bytes which can be written at once during a page write
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#define MAX_PAGE_WRITE 32
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// This is the 24LC32's capacity in bytes
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#define EEPROM_SIZE 4096
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// Acknowledge polling can be used to see when a write cycle is complete
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// Wait for the i2c slave to acknowledge our empty write
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bool ack_poll(uint8_t i2c_addr, i2c_inst_t *i2c_instance) {
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int timeout = 100;
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for (int i = 0; i < timeout; i++) {
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if (i2c_write_blocking(i2c_instance, i2c_addr, NULL, 1, false) == 1) {
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return true;
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}
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sleep_ms(1);
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}
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printf("ack timeout\n");
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return false;
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}
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// Read num bytes of memory starting at given address into result
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bool read_eeprom(uint16_t address, uint8_t *result, uint16_t num, uint8_t i2c_addr, i2c_inst_t *i2c_instance) {
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if ((address + num - 1) > EEPROM_SIZE) {
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printf("ERROR: Tried to read memory outside EEPROM's range.\n");
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return false;
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}
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for (int i = 0; i < num; i++) {
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uint8_t byte1 = (uint8_t)(address >> 8);
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uint8_t byte2 = (uint8_t)(address);
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uint8_t buf[2] = {byte1, byte2};
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i2c_write_blocking(i2c_instance, i2c_addr, buf, 2, true);
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i2c_read_blocking(i2c_instance, i2c_addr, (result + i), 1, false);
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address++;
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}
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return true;
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}
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// Write a single byte of data at a specified address in memory
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bool byte_write_eeprom(uint16_t address, uint8_t data, uint8_t i2c_addr, i2c_inst_t *i2c_instance) {
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if (address >= EEPROM_SIZE) {
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printf("ERROR: Tried to write to memory outside EEPROM's range.\n");
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return false;
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}
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uint8_t byte1 = (uint8_t)(address >> 8);
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uint8_t byte2 = (uint8_t)(address);
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uint8_t buf[3] = {byte1, byte2, data};
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i2c_write_blocking(i2c_instance, i2c_addr, buf, 3, false);
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// ack_poll to wait for write to be complete
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return ack_poll(i2c_addr, i2c_instance);
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}
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// Write a block of data to eeprom
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bool page_write_eeprom(uint16_t address, uint8_t *data, uint8_t num, uint8_t i2c_addr, i2c_inst_t *i2c_instance) {
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if (num > MAX_PAGE_WRITE) {
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printf("ERROR: Tried to write more than 32 bytes.\n");
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return false;
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} else if ((address + num - 1) > EEPROM_SIZE) {
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printf("ERROR: Tried to write to memory outside EEPROM's range.\n");
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return false;
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}
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uint8_t byte1 = (uint8_t)(address >> 8);
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uint8_t byte2 = (uint8_t)(address);
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uint8_t buf[2 + num];
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buf[0] = byte1;
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buf[1] = byte2;
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// transfer data into buffer
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for (int i = 0; i < num; i++) {
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buf[i + 2] = data[i];
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}
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i2c_write_blocking(i2c_instance, i2c_addr, buf, 2 + num, false);
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// ack_poll to wait for write to be complete
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return ack_poll(i2c_addr, i2c_instance);
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}
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// Initialise i2c for given gpio at given frequency
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void eeprom_init(int sda_pin, int scl_pin, int freq, i2c_inst_t *i2c_instance) {
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i2c_init(i2c_instance, freq);
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gpio_set_function(sda_pin, GPIO_FUNC_I2C);
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gpio_set_function(scl_pin, GPIO_FUNC_I2C);
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gpio_pull_up(sda_pin);
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gpio_pull_up(scl_pin);
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}
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‎i2c/24lc32_i2c/24lc32_i2c_lib.h‎

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#ifndef PICO_I2C_EEPROM_LIB_H
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#define PICO_I2C_EEPROM_LIB_H
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#include "hardware/i2c.h"
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// Acknowledge polling can be used to see when a write cycle is complete
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// Wait for the i2c slave to acknowledge our empty write
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bool ack_poll(uint8_t i2c_addr, i2c_inst_t *i2c_instance);
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// Read num bytes of memory starting at given address into result
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bool read_eeprom(uint16_t address, uint8_t *result, uint16_t num, uint8_t i2c_addr, i2c_inst_t *i2c_instance);
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// Write a single byte of data at a specified address in memory
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bool byte_write_eeprom(uint16_t address, uint8_t data, uint8_t i2c_addr, i2c_inst_t *i2c_instance);
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// Write a block of data to eeprom
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bool page_write_eeprom(uint16_t address, uint8_t *data, uint8_t num, uint8_t i2c_addr, i2c_inst_t *i2c_instance);
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// Initialise i2c for given gpio at given frequency
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void eeprom_init(int sda_pin, int scl_pin, int freq, i2c_inst_t *i2c_instance);
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#endif

‎i2c/24lc32_i2c/CMakeLists.txt‎

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# Add libary
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add_library(24lc32_i2c_lib INTERFACE)
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target_sources(24lc32_i2c_lib INTERFACE
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${CMAKE_CURRENT_LIST_DIR}/24lc32_i2c_lib.c
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)
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target_include_directories(24lc32_i2c_lib INTERFACE
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${CMAKE_CURRENT_LIST_DIR}
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)
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target_link_libraries(24lc32_i2c_lib INTERFACE
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pico_stdlib
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hardware_i2c
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)
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# Add executable
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add_executable(24lc32_i2c
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example.c
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)
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target_link_libraries(24lc32_i2c
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24lc32_i2c_lib
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pico_stdlib
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hardware_i2c
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)
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pico_add_extra_outputs(24lc32_i2c)

‎i2c/24lc32_i2c/README.adoc‎

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= Reading and writing 24LC32 EEPROM via I2C
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This example code demonstrates how to read and write data from 24LC32 EEPROM. It contains a library with functions for reading data, writing single bytes, and writing pages; and an example which uses these functions.
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== Wiring information
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[[24lc32_i2c_wiring]]
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[pdfwidth=75%]
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.Wiring Diagram for 24LC32 EEPROM via I2C.
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image::24lc32_i2c.png[]
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== List of Files
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CMakeLists.txt:: CMake file to incorporate the example into the examples build tree.
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24lc32_i2c_lib.c:: Library containing functions to interact with 24LC32 eeprom via I2C.
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24lc32_i2c_lib.h:: Header file containing function declarations for the 24LC32 library.
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example.c:: The example code.
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== Bill of Materials
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.A list of materials required for the example
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[[24lc32_i2c-bom-table]]
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[cols=3]
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|===
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| *Item* | *Quantity* | Details
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| Breadboard | 1 | generic part
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| Raspberry Pi Pico (any) | 1 | https://www.raspberrypi.com/products/raspberry-pi-pico/
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| 24LC32-based breakout board | 1 | https://www.adafruit.com/product/5146
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| M/M Jumper wires | 4 | generic part
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|===

‎i2c/24lc32_i2c/example.c‎

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#include <stdio.h>
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#include "pico/stdlib.h"
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#include "hardware/i2c.h"
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#include "24lc32_i2c_lib.h"
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// Default I2C address of 24LC32
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#define I2C_ADDRESS 0x50
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int main() {
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stdio_init_all();
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eeprom_init(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, 400*1000, i2c_default);
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printf("24LC32 I2C EEPROM example\nStarting test...\n\n");
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// Write the byte at location 0x00 to 0
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byte_write_eeprom(0x00, 0, I2C_ADDRESS, i2c_default);
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// Make an array of integers from 1 to 31 and write the array to eeprom starting at 0x01
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uint8_t data_list[31];
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for (int i = 0; i < 31; i++) {
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data_list[i] = i + 1;
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}
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page_write_eeprom(0x01, data_list, 31, I2C_ADDRESS, i2c_default);
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// Read eeprom, and ensure we observe ascending integers from 0 to 31
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uint8_t result[32];
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read_eeprom(0x0, result, 32, I2C_ADDRESS, i2c_default);
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for (int i = 0; i < 32; i++) {
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printf("read: %i, expected: %i\n", result[i], i);
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if (result[i] != i) {
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printf("Unexpected read!\n");
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return 1;
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}
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}
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// Now re-write and re-read eeprom
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printf("\nReversing order...\n\n");
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for (int i = 0; i < 31; i++) {
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data_list[i] = 31 - i;
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}
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page_write_eeprom(0x00, data_list, 31, I2C_ADDRESS, i2c_default);
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byte_write_eeprom(0x1F, 0, I2C_ADDRESS, i2c_default);
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// Read eeprom, and ensure we observe descending integers from 31 to 0
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read_eeprom(0x0, result, 32, I2C_ADDRESS, i2c_default);
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for (int i = 0; i < 32; i++) {
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printf("read: %i, expected: %i\n", result[i], 31 - i);
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if (result[i] != 31 - i) {
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printf("Unexpected read!\n");
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return 1;
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}
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}
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printf("Test passed!\n");
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return 0;
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}

‎i2c/CMakeLists.txt‎

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add_subdirectory_exclude_platforms(pcf8523_i2c)
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add_subdirectory_exclude_platforms(ht16k33_i2c)
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add_subdirectory_exclude_platforms(slave_mem_i2c)
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add_subdirectory_exclude_platforms(24lc32_i2c)
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else()
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message("Skipping I2C examples as hardware_i2c is unavailable on this platform")
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endif()

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