Questions about LoRaMac-node for Class-B

goodshot · May 28, 2018, 2:47am

@brocaar

hi brocaar !

I have some questions about Lora-net/LoRaMac-node/branch/class_b

It will be much appreciate if I can get help from you

1、I use apps\LoRaMac\classB\NucleoL073

2、the code “TimerTime_t currentTime = TimerGetCurrentTime( );”

the fuction is getting the total millisecond ？
but TimerTime_t is uint32_t
so it has a overflow problem

for example

sysTime.Seconds=1527471204
sysTime.SubSeconds=469
so the currentTime will be (1527471204 *1000+469) & 0xFFFFFFFF=0xA460E875

but in LoRaMacClassBDeviceTimeAns fuction because of the total millisecond 's overflow problem

for example
when currentTime %128000=0
but systime(millisecond ) % 128 may ≠0

while the beacon will send at the time witch modulo 128 equal 0，so if I set the beacon RXwindow by “currentTime ”，the sysTime will diffrent from the gateway send the beacon

best regards !

brocaar · May 28, 2018, 6:44am

Sorry, but I can’t / don’t give any support on the LoRaMac-node Class-B code. But maybe somebody else can give a hand here

goodshot · May 28, 2018, 7:43am

@brocaar get that

by the way, do you know when gateway send data to the class b device during ping slot ,witch frequency does the gateway choose?

I read the <lorawantm_regional_parameters_v1.1rb_-_final> but I have not find the answer

thank you !

brocaar · May 28, 2018, 8:42am

That depends how you configure your gateway:

github.com

Lora-net/packet_forwarder/blob/master/lora_pkt_fwd/cfg/global_conf.json.PCB_E286.EU868.beacon#L192


        /* forward only valid packets */
        "forward_crc_valid": true,
        "forward_crc_error": false,
        "forward_crc_disabled": false,
        /* GPS configuration */
        "gps_tty_path": "/dev/ttyAMA0",
        /* GPS reference coordinates */
        "ref_latitude": 0.0,
        "ref_longitude": 0.0,
        "ref_altitude": 0,
        /* Beaconing parameters */
        "beacon_period": 128,
        "beacon_freq_hz": 869525000,
        "beacon_datarate": 9,
        "beacon_bw_hz": 125000,
        "beacon_power": 14,
        "beacon_infodesc": 0
    }
}

The frequencies used per region are documented in the Regional Parameters Specification.

goodshot · May 28, 2018, 9:03am

thanks for your reply

I know the beacon freq

I mean the ping freq

470CH

brocaar · May 28, 2018, 9:50am

That is up to you and will be synchronized between LoRa Server and your device using a mac-command Please refer to the LoRa Server configuration: https://www.loraserver.io/loraserver/install/config/