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time sync protocol: handling of end mark 0xff

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This commit is contained in:
Klaus K Wilting 2020-10-09 23:02:36 +02:00
parent ac82a5f19e
commit 92eb55b001
3 changed files with 45 additions and 40 deletions
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76
src/Timeserver/Nodered-Timeserver.json
View File

@ -1,41 +1,4 @@
[
{
"id": "b8bd33fd.61caa",
"type": "function",
"z": "449c1517.e25f4c",
"name": "Timeserver Logic",
"func": "/* LoRaWAN Timeserver\n\nVERSION: 1.3\n\nconstruct 6 byte timesync_answer from gateway timestamp and node's time_sync_req\n\nbyte meaning\n1 sequence number (taken from node's time_sync_req)\n2..5 current second (from GPS epoch starting 1980)\n6 1/250ths fractions of current second\n\n*/\n\nfunction timecompare(a, b) {\n \n const timeA = a.time;\n const timeB = b.time;\n\n let comparison = 0;\n if (timeA > timeB) {\n comparison = 1;\n } else if (timeA < timeB) {\n comparison = -1;\n }\n return comparison;\n}\n\nlet confidence = 1000; // max millisecond diff gateway time to server time\n\n// guess if we have received a valid time_sync_req command\nif (msg.payload.payload_raw.length != 1)\n return;\n\nvar deviceMsg = { payload: msg.payload.dev_id };\nvar seqNo = msg.payload.payload_raw[0];\nvar seqNoMsg = { payload: seqNo };\nvar gateway_list = msg.payload.metadata.gateways;\n\n// filter all gateway timestamps that have milliseconds part (which we assume have a \".\")\nvar gateways = gateway_list.filter(function (element) {\n return (element.time.includes(\".\"));\n});\n\nvar gateway_time = gateways.map(gw => {\n return {\n time: new Date(gw.time),\n eui: gw.gtw_id,\n }\n });\nvar server_time = new Date(msg.payload.metadata.time);\n\n// validate all gateway timestamps against lorawan server_time (which is assumed to be recent)\nvar gw_timestamps = gateway_time.filter(function (element) {\n return ((element.time > (server_time - confidence) && element.time <= server_time));\n});\n\n// if no timestamp left, we have no valid one and exit\nif (gw_timestamps.length === 0) {\n var notavailMsg = { payload: \"n/a\" };\n var notimeMsg = { payload: 0xff }; \n var buf2 = Buffer.alloc(1);\n msg.payload = new Buffer(buf2.fill(0xff));\n msg.port = 9; // Paxcounter TIMEPORT\n return [notavailMsg, notavailMsg, deviceMsg, seqNoMsg, msg];}\n\n// sort time array in ascending order to find most recent timestamp for time answer\ngw_timestamps.sort(timecompare);\n\nvar timestamp = gw_timestamps[0].time;\nvar eui = gw_timestamps[0].eui;\nvar offset = server_time - timestamp;\n\nvar seconds = Math.floor(timestamp/1000);\nvar fractions = (timestamp % 1000) / 4;\n\nlet buf = new ArrayBuffer(6);\nnew DataView(buf).setUint8(0, seqNo);\nnew DataView(buf).setUint32(1, seconds);\nnew DataView(buf).setUint8(5, fractions);\n\nmsg.payload = new Buffer(new Uint8Array(buf));\nmsg.port = 9; // Paxcounter TIMEPORT\nvar euiMsg = { payload: eui };\nvar offsetMsg = { payload: offset };\n\nreturn [euiMsg, offsetMsg, deviceMsg, seqNoMsg, msg];",
"outputs": 5,
"noerr": 0,
"x": 330,
"y": 327,
"wires": [
[
"c9a83ac9.50fd18",
"6aeb3720.a89618",
"6ac55bbe.12ac54"
],
[
"de908e66.b6fd3"
],
[
"d5a35bab.44cb18"
],
[
"3a661f0a.c61b1"
],
[
"9b4f492d.fbfd18"
]
],
"outputLabels": [
"gw_eui",
"offset_ms",
"device",
"seq_no",
"time_sync_ans"
]
},
{
"id": "9b4f492d.fbfd18",
"type": "change",
@ -214,12 +177,49 @@
"id": "15980d22.6f4663",
"type": "comment",
"z": "449c1517.e25f4c",
"name": "LoRaWAN Timeserver v1.3",
"name": "LoRaWAN Timeserver v1.4",
"info": "PLEASE NOTE: There is a patent filed for the time sync algorithm used in the\ncode of this file. The shown implementation example is covered by the\nrepository's licencse, but you may not be eligible to deploy the applied\nalgorithm in applications without granted license by the patent holder.",
"x": 150,
"y": 47,
"wires": []
},
{
"id": "b8bd33fd.61caa",
"type": "function",
"z": "449c1517.e25f4c",
"name": "Timeserver Logic",
"func": "/* LoRaWAN Timeserver\n\nVERSION: 1.4\n\nconstruct 6 byte timesync_answer from gateway timestamp and node's time_sync_req\n\nbyte meaning\n1 sequence number (taken from node's time_sync_req)\n2..5 current second (from GPS epoch starting 1980)\n6 1/250ths fractions of current second\n\n*/\n\nfunction timecompare(a, b) {\n \n const timeA = a.time;\n const timeB = b.time;\n\n let comparison = 0;\n if (timeA > timeB) {\n comparison = 1;\n } else if (timeA < timeB) {\n comparison = -1;\n }\n return comparison;\n}\n\nlet confidence = 1000; // max millisecond diff gateway time to server time\nlet TIME_SYNC_END_FLAG = 255;\n\n// guess if we have received a valid time_sync_req command\nif (msg.payload.payload_raw.length != 1)\n return;\n\nvar deviceMsg = { payload: msg.payload.dev_id };\nvar seqNo = msg.payload.payload_raw[0];\nvar seqNoMsg = { payload: seqNo };\nvar gateway_list = msg.payload.metadata.gateways;\n\n// don't answer on TIME_SYNC_END_FLAG\nif (seqNo == TIME_SYNC_END_FLAG)\n return;\n\n// filter all gateway timestamps that have milliseconds part (which we assume have a \".\")\nvar gateways = gateway_list.filter(function (element) {\n return (element.time.includes(\".\"));\n});\n\nvar gateway_time = gateways.map(gw => {\n return {\n time: new Date(gw.time),\n eui: gw.gtw_id,\n }\n });\nvar server_time = new Date(msg.payload.metadata.time);\n\n// validate all gateway timestamps against lorawan server_time (which is assumed to be recent)\nvar gw_timestamps = gateway_time.filter(function (element) {\n return ((element.time > (server_time - confidence) && element.time <= server_time));\n});\n\n// if no timestamp left, we have no valid one and exit\nif (gw_timestamps.length === 0) {\n var notavailMsg = { payload: \"n/a\" };\n var notimeMsg = { payload: 0xff }; \n var buf2 = Buffer.alloc(1);\n msg.payload = new Buffer(buf2.fill(0xff));\n msg.port = 9; // Paxcounter TIMEPORT\n return [notavailMsg, notavailMsg, deviceMsg, seqNoMsg, msg];}\n\n// sort time array in ascending order to find most recent timestamp for time answer\ngw_timestamps.sort(timecompare);\n\nvar timestamp = gw_timestamps[0].time;\nvar eui = gw_timestamps[0].eui;\nvar offset = server_time - timestamp;\n\nvar seconds = Math.floor(timestamp/1000);\nvar fractions = (timestamp % 1000) / 4;\n\nlet buf = new ArrayBuffer(6);\nnew DataView(buf).setUint8(0, seqNo);\nnew DataView(buf).setUint32(1, seconds);\nnew DataView(buf).setUint8(5, fractions);\n\nmsg.payload = new Buffer(new Uint8Array(buf));\nmsg.port = 9; // Paxcounter TIMEPORT\nvar euiMsg = { payload: eui };\nvar offsetMsg = { payload: offset };\n\nreturn [euiMsg, offsetMsg, deviceMsg, seqNoMsg, msg];",
"outputs": 5,
"noerr": 0,
"x": 330,
"y": 327,
"wires": [
[
"c9a83ac9.50fd18",
"6aeb3720.a89618",
"6ac55bbe.12ac54"
],
[
"de908e66.b6fd3"
],
[
"d5a35bab.44cb18"
],
[
"3a661f0a.c61b1"
],
[
"9b4f492d.fbfd18"
]
],
"outputLabels": [
"gw_eui",
"offset_ms",
"device",
"seq_no",
"time_sync_ans"
]
},
{
"id": "c9a83ac9.50fd18",
"type": "debug",

7
src/Timeserver/timeserver.java
View File

@ -1,6 +1,6 @@
/* LoRaWAN Timeserver
VERSION: 1.3
VERSION: 1.4
construct 6 byte timesync_answer from gateway timestamp and node's time_sync_req
@ -26,6 +26,7 @@ function timecompare(a, b) {
}
let confidence = 1000; // max millisecond diff gateway time to server time
let TIME_SYNC_END_FLAG = 255;
// guess if we have received a valid time_sync_req command
if (msg.payload.payload_raw.length != 1)
@ -36,6 +37,10 @@ var seqNo = msg.payload.payload_raw[0];
var seqNoMsg = { payload: seqNo };
var gateway_list = msg.payload.metadata.gateways;
// don't answer on TIME_SYNC_END_FLAG
if (seqNo == TIME_SYNC_END_FLAG)
return;
// filter all gateway timestamps that have milliseconds part (which we assume have a ".")
var gateways = gateway_list.filter(function (element) {
return (element.time.includes("."));

2
src/timesync.cpp
View File

@ -148,7 +148,7 @@ void IRAM_ATTR timesync_processReq(void *taskparameter) {
// send timesync end char to show timesync was successful
payload.reset();
payload.addByte(TIME_SYNC_END_FLAG);
SendPayload(RCMDPORT, prio_high);
SendPayload(TIMEPORT, prio_high);
goto Finish;
Fail: