Hello, I am new to Particle and using the Photon module. I am connecting several pairs of photon devices and trying to store the “paired” device ID in non-volatile memory. I’ve had success using the EEPROM functions, get() and put() to store and read a 24 char string (the size of the device IDs), …

Shouldn’t you first EEPROM.get() the data and only EEPROM.put() when the result of get() indicates a new device? The way I see this (since you don’t show the rest of your code) pairedID only gets populated in that function, or where and how else? Could you show the rest of your code?

Hello, True, it would make sense to build a checking mechanism into this function, but I don’t see how that would solve the problem I am having. pairedID is a global variable and is initially populated using EEPROM.get() in setup(). See below. //Definition under global variables: String m…

Hi @jameson @rickkas7 has this very nice post showing how to write many types of data into EEPROM. [image] Need explanation for EEPROM usage (generally and on Photon) Here’s an example of reading and writing all sorts of data into EEPROM. // EEPROM sample code // EEPROM Documentatio…

I’d always favour C strings over String objects - there I exactly know what’s going on :wink: The thing with objects is that they need to be serializable in order to be stored away, and I doubt this is happening with EEPROM.put() and EEPROM.get() for any object. I’d rather think you just get the s…

Yes, what ScruffR said. Saving a String object using EEPROM.put() doesn’t work as you’d think it should - it won’t save the contents of the string. The reason is that the underlying code assumes a fixed-size primitive type (int, double, etc.) or structure. The code is: template <typename T> co…

Thanks guys! Got it working. I first tried casting the String as (const char*) in EEPROM.put() and also tried using the .c_str() function, but neither worked. (They may have been storing the first character in the String, but can’t verify this). However, I did get it working properly by using C st…

[image] jameson: The only thing I don't understand is that the char arrays need to be 25 bytes to fully capture the device IDs, which seem to only be 24 chars long. C char arrays use a trailing zero character to tell where the end of the string is, so that is normal.

Non-Volatile Data Storage Help

Firmware

bko June 29, 2016, 11:43am 4

Hi @jameson

@rickkas7 has this very nice post showing how to write many types of data into EEPROM.

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Non-Volatile Data Storage Help

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