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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)

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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

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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.

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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.

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Expected output of the example below.

EEPROM size: 6144Data:3.141590hello 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);}