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Fix coding of the "Margin" field of the "DevStatusAns" command payload #131

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merged 9 commits into from
Sep 27, 2018
Merged

Fix coding of the "Margin" field of the "DevStatusAns" command payload #131

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cc0d691
Change the maxium allowed value of margin from 254 to 31
frazar Sep 24, 2018
62a8177
Revert "Change the maxium allowed value of margin from 254 to 31"
frazar Sep 25, 2018
5a0119b
Move comment to correct line
frazar Sep 25, 2018
4ff49b2
Add the `devsAnsMargin` field to the `lmic_t` struct`
frazar Sep 25, 2018
f619fd1
Update `devsAnsMargin` when receiving a 'DevStatusReq' command
frazar Sep 25, 2018
95ea3c0
Add comments
frazar Sep 25, 2018
071be04
Fix typo
frazar Sep 25, 2018
c79676d
Set the correct value for margin
frazar Sep 26, 2018
99848e0
Fix typo
frazar Sep 26, 2018
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10 changes: 8 additions & 2 deletions src/lmic/lmic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -609,6 +609,10 @@ scan_mac_cmds(
}
case MCMD_DEVS_REQ: {
LMIC.devsAns = 1;
// LMIC.snr is SNR time 4, convert to real SNR; rounding towards zero.
const int snr = (LMIC.snr + 2) / 4;
// per [1.02] 5.5. the margin is the SNR.
LMIC.devAnsMargin = (u1_t)(0b00111111 & (snr <= -32 ? -32 : snr >= 31 ? 31 : snr));
oidx += 1;
continue;
}
Expand Down Expand Up @@ -838,11 +842,13 @@ static bit_t decodeFrame (void) {
if( LMIC.adrAckReq != LINK_CHECK_OFF )
LMIC.adrAckReq = LINK_CHECK_INIT;

// Process OPTS
int m = LMIC.rssi - RSSI_OFF - getSensitivity(LMIC.rps);
LMIC.margin = m < 0 ? 0 : m > 31 ? 31 : m;
// for legacy reasons, LMIC.margin is set to the unsigned sensitivity. It can never be negative.
// it's only computed for legacy clients
LMIC.margin = m < 0 ? 0 : m > 254 ? 254 : m;

#if LMIC_DEBUG_LEVEL > 0
// Process OPTS
LMIC_DEBUG_PRINTF("%lu: process options (olen=%#x)\n", os_getTime(), olen);
#endif

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3 changes: 2 additions & 1 deletion src/lmic/lmic.h
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Expand Up @@ -253,7 +253,7 @@ struct lmic_t {

u4_t freq;
s1_t rssi;
s1_t snr;
s1_t snr; // LMIC.snr is SNR time 4
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rps_t rps;
u1_t rxsyms;
u1_t dndr;
Expand Down Expand Up @@ -315,6 +315,7 @@ struct lmic_t {
u1_t margin;
bit_t ladrAns; // link adr adapt answer pending
bit_t devsAns; // device status answer pending
s1_t devAnsMargin; // SNR value between -32 and 31 (inclusive) for the last successfully received DevStatusReq command
u1_t adrEnabled;
u1_t moreData; // NWK has more data pending
#if !defined(DISABLE_MCMD_DCAP_REQ)
Expand Down