The meters never get credentials. The Pi logs in as one device, and on that device you turn on This device is a gateway. Its profile must use the default v1/ topic scheme. Then it publishes for the children with QoS 1, telemetry keyed by the child’s name:
topic: v1/gw/telemetry
{
"Meter 1": {"values": {"kwh": 1203.4, "voltage": 229.8}},
"Meter 2": {"values": {"kwh": 88.1}}
}A child is created the first time the gateway mentions it. Send v1/gw/connect with a type that is exactly the name of one of your profiles if you want it to land on that profile; otherwise it gets the gateway profile’s Profile of new children. Commands for a meter reach the Pi on v1/gw/rpc.