Sumar variables de dos contadores modbus

[E1cid]

In your original function you used msg.payload[0] in
obj.payload.W=(msg.payload[0]/1 << 16) >> 16; to access the buffer.
After the join node both device buffers are at
msg.payload.unit1[0] one buffer from sensor 1
and
msg.payload.unit3[0] one bffer from sensor 2