The "Margin" field of the "DevStatusAns" command payload is wrongly encoded

[frazar]

Tested with Arudino Mega 2560 connected to RFM95 module.

Add the following two lines to project_config/lmic_project_config.h:

#define LMIC_DEBUG_LEVEL 2
#define LMIC_PRINTF_TO Serial

After running a slightly modified version of the ttn-otaa sketch, this is the output on the Serial.

Serial connection enstablished.
RXMODE_RSSI
62657: engineUpdate, opmode=0x808
Packet queued
62708: EV_JOINING
62778: engineUpdate, opmode=0xc
273627: engineUpdate, opmode=0xc
273909: EV_TXSTART
273934: engineUpdate, opmode=0x88c
273992: TXMODE, freq=868100000, len=23, SF=7, BW=125, CR=4/5, IH=0
582073: setupRx1 txrxFlags 00 --> 01
start single rx: now-rxtime: 6
582161: RXMODE_SINGLE, freq=868100000, SF=7, BW=125, CR=4/5, IH=0
593337: EV_JOINED
netid: 0
devaddr: XXXXXXXX
artKey: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
nwkKey: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
593699: engineUpdate, opmode=0x808
594248: EV_TXSTART
594274: engineUpdate, opmode=0x888
594393: TXMODE, freq=868100000, len=19, SF=7, BW=125, CR=4/5, IH=0
653595: setupRx1 txrxFlags 0x1 --> 01
start single rx: now-rxtime: 4294967238
653657: RXMODE_SINGLE, freq=868100000, SF=7, BW=125, CR=4/5, IH=0
662938: process options (olen=0x6)
662975: LinkAdrReq: p1:52 chmap:0007 chpage:00 uprt:01 ans:87
663116: decodeFrame txrxFlags 0x1 --> 21
663333: Received downlink, window=RX1, port=-1, ack=0, txrxFlags=0x21
663705: EV_TXCOMPLETE (includes waiting for RX windows)
664010: engineUpdate, opmode=0x800
1289010: engineUpdate, opmode=0x808
1289466: EV_TXSTART
1289495: engineUpdate, opmode=0x888
1289554: TXMODE, freq=868300000, len=24, SF=7, BW=125, CR=4/5, IH=0
Packet queued
1349396: setupRx1 txrxFlags 0x21 --> 01
start single rx: now-rxtime: 4294967238
1349463: RXMODE_SINGLE, freq=868300000, SF=7, BW=125, CR=4/5, IH=0

Basically we can see that the Node is able to join the Lora network (593337: EV_JOINED), but fails to send the first uplink packet and keeps retrying.

Logging on the AWG ubuntu machine and checking the logs with journalctl -f -u loraserver I noticed the following lines appearing right after the node sends the "Packet queued" message:

Sep 24 20:20:15 ip-172-31-45-153 loraserver[18826]: time="2018-09-24T20:20:15Z" level=error msg="processing uplink frame error" data_base64=XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX error="create uplink frame-log error: marshal phypayload error: lorawan: max value of Margin is 31"

[terrillmoore]

I take it that this is not "The Things Network" as the network server? Definitely agree that this is a problem, but I need more context, as I've not seen this in my testing. (Need to figure out what additional test coverage is needed.)

[frazar]

Yes, sorry for not being clear enough. I'm using the LoRa Server software stack in a development environment.

[terrillmoore]

OK, cool! Another test case.... Interesting to think about how one could do hardware-in-the-loop testing with this.

You will probably find that this version of the LMIC stack doesn't do a great job with MAC command responses. See issue #87 for details. TL;DR: it doesn't built the response as it's parsing the request, so things can go back out of order (or not at all).