[AllanG]

Uncle_Bob, Werk_AG, thanks for the suggestions. I should have said that I've already tried defining TestMode as True but it has no effect at all. Here's the RX_Config tab contents as I have just tried again, unsuccessfully, to start up....

// --------------------------------------------------------------------------------------
// User configurable options
// --------------------------------------------------------------------------------------

#define Station_ID 0xA1 // Station_ID, use the same value in all TX units
#define Relay_ID 0xA3 // Relay_ID, use the same value in all WD units

// --- Define Software Operation Mode
#define Work_Mode 0 // Mode 0= Davis VP2 Emulation Mode, Mode 1= EasyWeather Mode

// --- Define your Display type
// --- Chosing TFT automatically disables the data logger function (no memory for both)
#define DisplayType 1 // 0= TFT, 1= LCD 20x4, 2= LCD 16x2

// --- Define Backlight TimeOut
// --- With old RX boards, version <= 3.01 always set this value to 0
const byte BackLight_Timeout = 15; // Timeout for display backlight in minutes (1 to 255). 0 = Always ON

// --- Define Display unit Formats --------------------------------------------
#define Date_Time_Format 0 // 0 for dd-mm-yyyy, 1 for yyyy/mm/dd
#define Temp_Display_Unit 0 // 0 for ºC, 1 for ºF
#define ATM_Display_Unit 0 // 0 for mBar, 1 for inHg
#define Rain_Display_Unit 0 // 0 for mm (no other options)
#define Wind_Display_Unit 1 // 0 for Km/h, 1 for mph, 2 for m/s, 3 for Knots

// --- Fine adjusts for Inside Temperature and Barometer
const int TemperaturaInt_offset = 0; // Inside Temperature Fine Adjust in Tenths of Degree (-4 = -0,4ºC)
const float pressure_offset = -1.0; // Pressure Fine Adjust in mB

// --- Some Data from your Weather Station location
#define LATITUDE 534 // Put here your Station latitude in tenths of degrees North
#define LONGITUDE -28 // Put here your Station longitude in tenths of degrees (minus for West)
#define ELEVATION 68 // Put here your Station height above sea level in Meters

// --- Define Roll Over Hour for Meteorological Day
#define MeteoDay_HStart 0 // Use values from 0 to 23

// --- Define Wind Speed and Wind Gust resolution
#define VP2_WindRes 2 // If set to 2, set Cumulus Wind Speed and Wind Gust multipliers to 0.448. Wind Resolution 0.72 Km/h
// If set to 1, set Cumulus Wind Speed and Wind Gust multipliers to 0.224. Wind Resolution 0.36 Km/h
// WARNING !!! Setting this variable to 1 allows a better wind speed and gust resolution,
// but also limits both of them, to a maximum reading of just 91.8 Km/h
// This setting only have effect when the software is used in Davis VP2 emulation mode
// If set to 0, system uses Standard Davis 1 mph wind resolution.

// --- Define the type of your inside Temperature / Humidity Sensor
#define InsideTH_Sensor 1 // 0= DHT22, 1= HTU21D

// ---- Lets define the source or type of our main outside sensors
// ---- If you have all the sensors connected to only one TX board, always select Unit 0 as source
// ---- Define the source of your main Temperature / Humidity sensor
#define TH_OutUnit 0 // 0 for Temp/Hum sensor connected to TX_Unit 0, 1 for Temp/Hum sensor connected to TX_Unit 1
// --- Define your main outside Temperature / Humidity Sensor
#define MainOutTH_Sensor 0 // 0 for sensor type SHT21 or HTU21D, 1 for sensor type SHT1x or DHT22
// ---- Define the source of your Main Wind sensor
#define WIND_OutUnit 0 // 0 for Wind instruments connected to TX_Unit 0, 1 for TX_Unit 1
// ---- Define the source of your main Rain Gauge
#define RAIN_OutUnit 0 // 0 for Rain Gauge connected to TX_Unit 0, 1 for TX_Unit 1, 2 for Auriol RF Rain Gauge
// ---- Define the source of your main Solar / UV sensores
#define SRUV_OutUnit 9 // 0 for Solar Rad / UV sensors connected to TX_Unit 0, 1 for TX_Unit1, 9 for not used
// ---- Define installed Solar / UV Sensors
#define Solar_Sensor 9 // 0 for not present; 1 for present
#define UV_Sensor 9 // 0 for not present; 1 for present


// ---- Extra Sensors Mapping
// ---- Define the TX source and sensor number of each of the five extra sensors, insert 9 if not used.
// ---- Sensor number 0 is for type SHT21 or HTU21D. Sensor number 1 is for type SHT1x or DHT22
// ---- First field = TX unit number, Second field = Sensor number (0 or 1) in the TX unit
// ---- Example: {0,1} - First extra sensor, is sensor 1 from TX unit0
// {1,0} - Second extra sensor, is sensor 0 from TX unit1
#define ExtraSensors { {9,9},{9,9},{9,9},{9,9},{9,9} }


// ---- Broadacasting Data Settings
#define Relay_Data 1 // 0= Disables Data Relay, 1= Enables Data Relay

// ---- Data Logger Settings
#define Logger_Enable 1 // 0= Disable 1= Enable
byte ARCHIVE_PERIOD = 1; // Default Archive Period in Minutes (Usable values: 1, 5, 10, 15, 30, 60 or 120)

// ---- Define your RX board main version number
#define Board_Version 5 // Use 4 for all RX boards v4.xx, use 5 for RX boards v5.xx

// ---- Test Mode ON/OFF
#define TestMode true // false= Normal working mode, true= Test mode only (no logger, no usb connection)

// ---------------------------------------------------------------------------------------------------
// End of user configurable options
// ---------------------------------------------------------------------------------------------------

(Indoor and outdoor temp/humidity sensors are both SHT21)


I've also made sure TX and RX are separated by 2-3 metres, started TX first, waited a minute or two then started the RX but still no change. I've left the RX module running for more than 30 minutes and it still doesn't complete initialisation - the Com_Led remains lit the whole time but the TX led doesn't light or even flash at all.

Any other things I should check or change - I'm probably making a very simple mistake somewhere??!!

Allan