ESP8266 Community Forum

Hi all,
I'm trying to store my wifi credentials on my Wemos D1 R2. I'm using the ESP library to access the flash memory and I'm having a heck of a time getting it figured out. I have written a test bed that demonstrates the problem. What I try to write to flash seems to write OK, but when I try to read it back, it never matches.

/*
* The purpose of this program is to initialize the flash memory on the
* board where configuration information is stored. This needs to be performed before the board
* is loaded with the final sketch
*/

#include <ESP8266WiFi.h>

#define CONFIG_SECTOR 0x80-4
#define CONFIG_ADDRESS ( CONFIG_SECTOR * 4096 )
#define IS_CONFIGURED 0xFEFE
#define NOT_CONFIGURED 0xFFFF

typedef struct {
int id;
char name[16];
char location[64];
byte macAddress[6]; // MAC address of the wifi
char ssid[64];
char pw[64];
} Configuration __attribute__ ((packed));

Configuration config;
Configuration verifyConfig;

byte deviceData[sizeof(config)];

// Serial Data
#define ReceivedBufferLength 20
char receivedBuffer[ReceivedBufferLength + 1]; // store the serial command
byte receivedBufferIndex = 0;

void setup() {
Serial.begin(115200);
Serial.println("");
config.id = NOT_CONFIGURED;
strcpy(config.name, "Unknown");
strcpy(config.location, "Unknown location");
WiFi.macAddress(config.macAddress); // Get the MAC address
strcpy(config.ssid, "********");
strcpy(config.pw, "********");

Serial.print("Original name = ");
Serial.println(config.name);

// Write the initialized configuration to the board.
Serial.println("Erasing the memory...");
ESP.flashEraseSector(CONFIG_SECTOR);
delay(1000); // Just in case timing matters after a write
Serial.println("Flashing the initialized configuration...");
ESP.flashWrite(CONFIG_ADDRESS, (uint32_t *)&config, (size_t)sizeof(config));
delay(1000); // Just in case timing matters after a write
// Verify what we've written
Serial.println("Verifying the written data...");
ESP.flashRead(CONFIG_ADDRESS, (uint32_t *)&config, (size_t)sizeof(config));
if(verifyConfig.id == NOT_CONFIGURED)
Serial.println("Initialized. Please unplug");
else {
Serial.print("Error verifying initialization. ID field read as ");
Serial.println(verifyConfig.id);
Serial.print("Name = ");
Serial.println(verifyConfig.name);
}
}

Any ideas what I am doing wrong? I need to be able to store the SSID and password onboard the wemos so that it will survive a loss of power. Thanks in advance!

You might find this GengusKahn's contribution to this post interesting:
viewtopic.php?f=160&t=13583
The WiFi library stores credentials in flash anyway, so you may not need this flash-writing sketch at all.
(The original poster and I wanted to prevent credentials being stored, so you probably won't find our contributions on that thread useful.)

Thanks for pointing me to that post. That help with the WiF aspect. However, I still need to store additional non-Wifi configuration information into flash (a device name, etc). The idea is to have someone with no wemos/arduino skills be able to set these values for their device via bluetooth and allow these setting to survive a power-down.

Looks like the Wifi part may be ok though!

- Jeff

I'm doing something very similar, but I'm not using a Wemos, or ESP.flash*
I'm using an ESP-07 and the EEPROM library. I don't know if that would suit your needs; but it's a possible alternative in case no-one answers your specific case.