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[WIP] Class B fixes #481

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[WIP] Class B fixes #481

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2226826
Fix mac cmd size retrieval
sualko Oct 21, 2019
9ed48ca
Set class B flag if pingable
sualko Oct 21, 2019
b7bee3f
Fix beacon frequence in europe
sualko Oct 22, 2019
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5 changes: 4 additions & 1 deletion src/lmic/lmic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -711,7 +711,7 @@ static CONST_TABLE(u1_t, macCmdSize)[] = {
static u1_t getMacCmdSize(u1_t macCmd) {
if (macCmd < 2)
return 0;
if (macCmd >= LENOF_TABLE(macCmdSize) - 2)
if ((macCmd - 2) >= LENOF_TABLE(macCmdSize))
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@terrillmoore terrillmoore Oct 21, 2019

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Ugh. Sorry about this one.

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@sualko sualko Oct 22, 2019

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No problem, but I'm wondering why 0 is returned in the error case, because in scan_mac_cmds I see no check except for line 887, which doesn't do what the comment says.

https://github.com/sualko/arduino-lmic/blob/cabf6fbcd4390fcc42102a47c0323b7dafc6723a/src/lmic/lmic.c#L887

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@terrillmoore terrillmoore Oct 22, 2019

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Yes, that's a bug too -- no test cases for bad mac commands, even in certification.

Should be if (cmdlen == 0 || cmdlen >> olen - oidx).

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@terrillmoore terrillmoore Feb 27, 2022

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This was fixed in 06b53c7, merged in #555 (and possibly before that, but that's the most recent change).

return 0;
return TABLE_GET_U1(macCmdSize, macCmd - 2);
}
Expand Down Expand Up @@ -1889,6 +1889,9 @@ static bit_t buildDataFrame (void) {
LMIC.frame[OFF_DAT_HDR] = HDR_FTYPE_DAUP | HDR_MAJOR_V1;
LMIC.frame[OFF_DAT_FCT] = (LMIC.dnConf | LMIC.adrEnabled
| (sendAdrAckReq() ? FCT_ADRACKReq : 0)
#if !defined(DISABLE_PING)
| ((LMIC.opmode & OP_PINGABLE) ? FCT_CLASSB : 0)
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@sualko sualko Oct 22, 2019

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@terrillmoore I think LMIC.opmode & OP_PINGABLE is the wrong check, because this is true after LMIC_setPingable is called, but this doesn't mean that the periodic read has started (e.g. the device has no beacon received yet). Is OP_TRACK the right mask?

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@terrillmoore terrillmoore Oct 22, 2019

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I guess. The spec is not clear about this at all. Here's the relevant text (starting at line 1147, page 43, spec 1.0.3

The end-device application requests the LoRaWAN layer 1147 to switch to Class B mode. The LoRaWAN layer in the end-device searches for a beacon and returns either a BEACON_LOCKED service primitive to the application if a network beacon was found and locked or a BEACON_NOT_FOUND service primitive. To accelerate the beacon discovery the LoRaWAN layer MAY use the “DeviceTimeReq” MAC command.

Once in Class B mode, the MAC layer sets to 1 the Class B bit of the FCTRL field of every uplink frame transmitted.

From context, it does appear possible that they mean the device has to be locked to the beacon. So I think it makes sense to change to OP_TRACK, as that bit is set exactly when EV_BEACON_FOUND is reported.

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@terrillmoore terrillmoore Feb 27, 2022

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Fixing as part of #208 major update.

#endif // ndef DISABLE_PING
| (end-OFF_DAT_OPTS));
os_wlsbf4(LMIC.frame+OFF_DAT_ADDR, LMIC.devaddr);

Expand Down