Documented the message sent when holding the reset button.

Also dug into what the "meter join" response value should be.

docs/protocol.md

@@ -11,6 +11,7 @@ Each message sent or received begins with a `$` (hex 24).  Messages end with a c
 | m        |  0x6d  | Get mac address (of the MGM111)|
 | i        |  0x69  | Get install code |
 | f        |  0x66  | Get firmware version |
+| d        |  0x64  | Sent after holding the reset button for 5 seconds |
 
 ## Sending messages
 
@@ -43,7 +44,7 @@ The mac address reponse bytes are in reverse order, if the device responds with
 The install code bytes are not swapped like the mac address payload.
 
 #### Meter join response payload
-This always returns a 0x01 value even if the Vue is not in range of the meter.
+Seems to return 0x01 even if the Vue is not in range of the meter and seems to return 0x00 before ever being provisioned with the meter. At the least, `1` is good and `0` is bad.
 
 #### Meter reading response payload
 The meter response payload has its own page [protocol-meter-reading.md](protocol-meter-reading.md)

src/emporia_vue_utility.h

@@ -25,7 +25,7 @@
 // 10 to 30 seconds, so "5" is usually fine.
 // You might try setting this to "1" to see if your meter has
 // new values more often
-#define METER_READING_INTERVAL 5
+#define METER_READING_INTERVAL 30
 
 // How often to attempt to re-join the meter when it hasn't
 // been returning readings
@@ -86,7 +86,7 @@ class EmporiaVueUtility : public Component,  public UARTDevice {
             uint16_t import_wh; // Payload Bytes 7 to 8
             byte unknown9[8];   // Payload Bytes 9 to 16
             uint16_t export_wh; // Payload Bytes 17 to 18
-            byte unknown19[21]; // Payload Bytes 19 to 38
+            byte unknown19[21]; // Payload Bytes 19 to 39
             uint32_t watts;     // Payload Bytes 40 to 43 : Starts with 0x2A, only use the last 24 bits.
         } __attribute__((packed));
 
@@ -495,6 +495,10 @@ class EmporiaVueUtility : public Component,  public UARTDevice {
 
         void handle_resp_meter_join() {
             ESP_LOGD(TAG, "Got meter join response");
+            // Reusing Ver struct because both have a single byte payload value.
+            struct Ver *ver;
+            ver = &input_buffer.ver;
+            ESP_LOGI(TAG, "Join response value: %d", ver->value);
         }
 
         int handle_resp_mac_address() {