SX1302_UDP_Packet_Forwarder

SX1302 Modified UDP Packet Forwarder

This modified version of the Semtech SX1302 UDP Packet Forwarder addresses two issues

1) On TTN the inclusion of the "temp" data element in the stats datagram prevents the datagram being received by TTN 2) Not all SX1302 gateway modules include a stts751 temperature sensor. To overcome the need to install an external I2C temperature sensor a preset temperature value can be set

The following commands have been added and are included in the global_config.json file

Issue 1 - to control the "temp" data element

"temperature_active":false,

The "temp" data element in "stat" datagram" can be included or excluded. If this line is missing the default value is true and the temp variable is included in the stat datagram To send temperature data element set it to true. Too prevent sending the "temp" set it to false.

Issue 2 - a lack of temperature sensor

"temperature_sensor": true,

Some SX1302 gateway modules do not have a stts751 temperature sensor installed. As a result the packet forwarder will fail to start. Where the sensor is installed place use the value of "true" and the sensor will be used. Where there is no sensor, use "false". The default value (if the line is not included in global_config.json) is true

"temperature_value": 25.0

When there is no sensor, use the command to set the expected gateway temperature to a set value. This is used in the calculation of RSSI If "temperature_sensor" was set to "true" then the sensor is used to measure temperature and the variable is ignore If the line is missing the default value is 20.0C

Files and Installation

You only need to copy the file lora_pkt_fwd.

Use the attached version of global_config.json as a reference to demonstrate how to add lines to your existing file.

The third file reset_lgw.sh has not been modified, use your existing file, its only included to provide a complete set of files.

More Detail about the "temp" data element in the stat datagram

SX1301 UDP Packet Forwarder follows what I think is the original gateway-to-server protocol whereas the more recent SX1302 UDP Packet Forwarder follows version v1.3 of the gateway-to-server protocol.

The observation described here relates to the behaviour with the stat datagram json { "stat":{...} }

Example

V1.3 gateway-to-server protocol             Original gateway-to-server protocol
(SX1302 stat datagram)                      (SX1301 stat datagram)
{"stat":{                                   {"stat":{                   
    "time":"2014-01-12 08:59:28 GMT",           "time":"2014-01-12 08:59:28 GMT",
    "lati":46.24000,                                    "lati":46.24000,
    "long":3.25230,                             "long":3.25230,
    "alti":145,                                 "alti":145,
    "rxnb":2,                                   "rxnb":2,
    "rxok":2,                                   "rxok":2,
    "rxfw":2,                                   "rxfw":2,
    "ackr":100.0,                               "ackr":100.0,
    "dwnb":2,                                   "dwnb":2,
    "txnb":2,                                   "txnb":2
    "temp": 23.2                            }}
}}

Observation

TTN server ignores the "stat" datagram when using V1.3 of the gateway-to-server protocol

This can be observed on the console as the gateway is "Not Seen".

The only time the gateway "Last Seen" is updated is when a Lora radio packet is received and forwarded to the server.

By patching the SX1302 UDP packet forwarder and removing the temp data element both the V2 and V3 versions of the server operate correctly.

JoToSystems / SX1302_UDP_Packet_Forwarder

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