network_common.cpp: implement efuse serial number fallback logic

Author: mstegen

SmartEVSE-3/src/network_common.cpp

@@ -1425,7 +1425,11 @@ void WiFiSetup(void) {
     if (preferences.begin("KeyStorage", true) ) {                               // true = readonly
 //prevent compiler warning
 #if DBG == 1 || (DBG == 2 && LOG_LEVEL != 0)
-        uint16_t hwversion = preferences.getUShort("hwversion");                // 0x0101 (01 = SmartEVSE,  01 = hwver 01)
+        // Hardware version 01xx = SmartEVSE
+        // xx01 = v3.0 first batch
+        // xx02 = v3.0 second batch
+        // xx03 = v3.1 (ESP32-mini)
+        uint16_t hwversion = preferences.getUShort("hwversion");                
 #endif
         serialnr = preferences.getUInt("serialnr");
         String ec_private = preferences.getString("ec_private");
@@ -1443,6 +1447,12 @@ void WiFiSetup(void) {
         esp_efuse_read_block(EFUSE_BLK3, efuse_hwversion, 56, 16);
         esp_efuse_read_block(EFUSE_BLK3, efuse_serialnr, 72, 24);
 
+        // check if we can use the serialnr in the efuses if the nvs version was erased
+        uint32_t efuseserialnr = efuse_serialnr[0]+(efuse_serialnr[1]<<8)+(efuse_serialnr[2]<<16);
+        // unprogrammed efuse values are zero's
+        if (efuseserialnr != serialnr && !efuseserialnr && !serialnr) {
+            serialnr = efuseserialnr;
+        }  
         //_LOG_A("Private key: ");
         //for (uint8_t x=0; x<32; x++) _LOG_A_NO_FUNC("%02x",efuse_block1[x]);
         //_LOG_A_NO_FUNC(" hwver: %02x%02x serialnr: %u\n", efuse_hwversion[1], efuse_hwversion[0], efuse_serialnr[0]+(efuse_serialnr[1]<<8));