AP_GPS: added automatic config of TMODE on F9

the Drotek F9 GPS ships with TMODE enabled, which means we don't get a
3D fix.

This also adds the VALGET/VALSET msgs we will need for automatic
moving baseline config

libraries/AP_GPS/AP_GPS_UBLOX.cpp

@@ -210,8 +210,13 @@ AP_GPS_UBLOX::_request_next_config(void)
         } else {
             _unconfigured_messages &= ~CONFIG_VERSION;
         }
-        // no need to send the initial rates, move to checking only
-        _next_message = STEP_PVT;
+        break;
+    case STEP_TMODE:
+        if (_hardware_generation >= UBLOX_F9) {
+            if (!_configure_valget(ConfigKey::TMODE_MODE)) {
+                _next_message--;
+            }
+        }
         break;
     default:
         // this case should never be reached, do a full reset if it is hit
@@ -870,8 +875,36 @@ AP_GPS_UBLOX::_parse_gps(void)
             return false;
         }
 #endif // CONFIGURE_PPS_PIN
+        case MSG_CFG_VALGET: {
+            uint8_t cfg_len = _payload_length - sizeof(ubx_cfg_valget);
+            const uint8_t *cfg_data = (const uint8_t *)(&_buffer) + sizeof(ubx_cfg_valget);
+            while (cfg_len >= 5) {
+                ConfigKey id;
+                memcpy(&id, cfg_data, sizeof(uint32_t));
+                cfg_len -= 4;
+                cfg_data += 4;
+                switch (id) {
+                case ConfigKey::TMODE_MODE: {
+                    uint8_t mode = cfg_data[0];
+                    cfg_len -= 1;
+                    cfg_data += 1;
+                    if (mode != 0) {
+                        // ask for mode 0, to disable TIME mode
+                        mode = 0;
+                        _configure_valset(ConfigKey::TMODE_MODE, 1, &mode);
+                        _unconfigured_messages |= CONFIG_TMODE_MODE;
+                    } else {
+                        _unconfigured_messages &= ~CONFIG_TMODE_MODE;
+                    }
+                    break;
+                }
+                default:
+                    // we don't know the length so we stop parsing
+                    return false;
+                }
+            }
+        }
         }
-           
     }
 
     if (_class == CLASS_MON) {
@@ -1325,6 +1358,52 @@ AP_GPS_UBLOX::_configure_message_rate(uint8_t msg_class, uint8_t msg_id, uint8_t
     return _send_message(CLASS_CFG, MSG_CFG_MSG, &msg, sizeof(msg));
 }
 
+/*
+ *  configure F9 based key/value pair - VALSET
+ */
+bool
+AP_GPS_UBLOX::_configure_valset(ConfigKey key, const uint8_t len, const uint8_t *value)
+{
+    if (_hardware_generation < UBLOX_F9) {
+        return false;
+    }
+    struct ubx_cfg_valset msg {};
+    uint8_t buf[sizeof(msg)+len];
+    if (port->txspace() < (int16_t)(sizeof(struct ubx_header)+sizeof(buf)+2)) {
+        return false;
+    }
+    msg.version = 1;
+    msg.layers = 7; // all layers
+    msg.transaction = 0;
+    msg.key = uint32_t(key);
+    memcpy(buf, &msg, sizeof(msg));
+    memcpy(&buf[sizeof(msg)], value, len);
+    auto ret = _send_message(CLASS_CFG, MSG_CFG_VALSET, buf, sizeof(buf));
+    return ret;
+}
+
+/*
+ *  configure F9 based key/value pair - VALGET
+ */
+bool
+AP_GPS_UBLOX::_configure_valget(ConfigKey key)
+{
+    if (_hardware_generation < UBLOX_F9) {
+        return false;
+    }
+    struct {
+        struct ubx_cfg_valget msg;
+        ConfigKey key;
+    } msg {};
+    if (port->txspace() < (int16_t)(sizeof(struct ubx_header)+sizeof(msg)+2)) {
+        return false;
+    }
+    msg.msg.version = 0;
+    msg.msg.layers = 0; // ram
+    msg.key = key;
+    return _send_message(CLASS_CFG, MSG_CFG_VALGET, &msg, sizeof(msg));
+}
+
 /*
  * save gps configurations to non-volatile memory sent until the call of
  * this message

libraries/AP_GPS/AP_GPS_UBLOX.h

@@ -77,13 +77,14 @@
 #define CONFIG_RATE_PVT      (1<<13)
 #define CONFIG_TP5           (1<<14)
 #define CONFIG_RATE_TIMEGPS  (1<<15)
+#define CONFIG_TMODE_MODE    (1<<16)
 #define CONFIG_LAST          (1<<16) // this must always be the last bit
 
 #define CONFIG_REQUIRED_INITIAL (CONFIG_RATE_NAV | CONFIG_RATE_POSLLH | CONFIG_RATE_STATUS | CONFIG_RATE_VELNED)
 
 #define CONFIG_ALL (CONFIG_RATE_NAV | CONFIG_RATE_POSLLH | CONFIG_RATE_STATUS | CONFIG_RATE_SOL | CONFIG_RATE_VELNED \
                     | CONFIG_RATE_DOP | CONFIG_RATE_MON_HW | CONFIG_RATE_MON_HW2 | CONFIG_RATE_RAW | CONFIG_VERSION \
-                    | CONFIG_NAV_SETTINGS | CONFIG_GNSS | CONFIG_SBAS)
+                    | CONFIG_NAV_SETTINGS | CONFIG_GNSS | CONFIG_SBAS | CONFIG_TMODE_MODE)
 
 //Configuration Sub-Sections
 #define SAVE_CFG_IO     (1<<0)
@@ -211,6 +212,23 @@ private:
         uint8_t scanmode2;
         uint32_t scanmode1;
     };
+    // F9 config keys
+    enum class ConfigKey : uint32_t {
+        TMODE_MODE = 0x20030001,
+    };
+    struct PACKED ubx_cfg_valset {
+        uint8_t version;
+        uint8_t layers;
+        uint8_t transaction;
+        uint8_t reserved[1];
+        uint32_t key;
+    };
+    struct PACKED ubx_cfg_valget {
+        uint8_t version;
+        uint8_t layers;
+        uint8_t reserved[2];
+        // variable length data, check buffer length
+    };
     struct PACKED ubx_nav_posllh {
         uint32_t itow;                                  // GPS msToW
         int32_t longitude;
@@ -467,6 +485,7 @@ private:
         ubx_cfg_gnss gnss;
 #endif
         ubx_cfg_sbas sbas;
+        ubx_cfg_valget valget;
         ubx_nav_svinfo_header svinfo_header;
         ubx_nav_relposned relposned;
 #if UBLOX_RXM_RAW_LOGGING
@@ -515,6 +534,8 @@ private:
         MSG_CFG_SBAS = 0x16,
         MSG_CFG_GNSS = 0x3E,
         MSG_CFG_TP5 = 0x31,
+        MSG_CFG_VALSET = 0x8A,
+        MSG_CFG_VALGET = 0x8B,
         MSG_MON_HW = 0x09,
         MSG_MON_HW2 = 0x0B,
         MSG_MON_VER = 0x04,
@@ -568,6 +589,7 @@ private:
         STEP_POLL_NAV, // poll NAV settings
         STEP_POLL_GNSS, // poll GNSS
         STEP_POLL_TP5, // poll TP5
+        STEP_TMODE, // set TMODE-MODE
         STEP_DOP,
         STEP_MON_HW,
         STEP_MON_HW2,
@@ -624,6 +646,8 @@ private:
     bool havePvtMsg;
 
     bool        _configure_message_rate(uint8_t msg_class, uint8_t msg_id, uint8_t rate);
+    bool        _configure_valset(ConfigKey key, const uint8_t len, const uint8_t *value);
+    bool        _configure_valget(ConfigKey key);
     void        _configure_rate(void);
     void        _configure_sbas(bool enable);
     void        _update_checksum(uint8_t *data, uint16_t len, uint8_t &ck_a, uint8_t &ck_b);