Skip to main content

How To: EEPROM

EEPROM is a special kind of memory. It is small (6 KB on Core Module chip) memory with a limited number of write/erase cycles. It is non-volatile memory - which means that it does not require power to retain stored information. This means that bytes written/stored inside the EEPROM will stay there until erased/rewritten (even without the power)

info

Don’t be afraid of limited W/E cycles. In standard conditions, the chip guarantees 100 000 cycles. Remember that those cycles are Write/Erase.

Reading from the EEPROM does not count, so it is completely safe to read from it as much as you wish.

References​

EEPROM Size​

TOWER Core Module has 6 KB EEPROM included. In case you need to find this value out inside your code, there is a function for this inside the SDK: size_t twr_eeprom_get_size(void)

Read/Write Example​

info

In this example, we will write the float value and string to EEPROM immediately after the Core Module boots. With every press of a button, the data will be retrieved from EEPROM and sent to the computer. To test that the memory is persistent you can try to comment both twr_eeprom_write lines out (after running the original example once).

It should still work and the debug should write the same string.

note

Please note that some of our modules (currently twr_radio_* module only) use a few last dozens of bytes in EEPROM. If you use those modules, remember to use the memory addresses from 0 up to 6000.

This makes sure that no data will be overwritten.

info

Expected output of the example below.

EEPROM size: 6144
Data:
3.141590
hello world!
EEPROM Test Code Example

#include <application.h>

twr_button_t button;

void button_event_handler(twr_button_t *self, twr_button_event_t event, void *event_param)
{
    (void) self;
    (void) event_param;

    if (event == TWR_BUTTON_EVENT_PRESS)
    {
        size_t eeprom = twr_eeprom_get_size();
        char readEeprom[13];
        float readFloat;

        twr_eeprom_read(0, &readFloat, 4);
        twr_eeprom_read(4, readEeprom, 12);
        readEeprom[12] = '\0';

        twr_log_debug("EEPROM size: %d\r\nData:\r\n%f\r\n%s", eeprom, readFloat, readEeprom);
    }
}

void application_init(void)
{
    twr_log_init(TWR_LOG_LEVEL_DEBUG, TWR_LOG_TIMESTAMP_ABS);

    float toWriteFloat = 3.14159;
    char toWrite[] = "hello world!";
    twr_eeprom_write(0, &toWriteFloat, sizeof(toWriteFloat));
    twr_eeprom_write(sizeof(toWriteFloat), toWrite, sizeof(toWrite));

    // Initialize button
    twr_button_init(&button, TWR_GPIO_BUTTON, TWR_GPIO_PULL_DOWN, false);
    twr_button_set_event_handler(&button, button_event_handler, NULL);
}