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NB-IoT

NB-IoT Functions​

This category contains functions specific to NB-IoT devices.

API NameBrief Description
api.nbSend()Sends a message to NB-IoT on specified IP, port, and protocol type. Multiple variants. See below.
api.nbReceiveBuffer()Activates, configures, and uses NB-IoT scratchpad buffer. Multiple variants. See below.
api.nbAT()Sends an AT command to NB-IoT module with specified timeout or uses defined commands. Multiple variants. See below.

api.nbSend()​

Sends a message to NB-IoT on specified IP, port, and protocol type.

API NameBrief Description
api.nbSend(addr, port, msg, timeout, type, nownewdatatimeout, rxport)Sends a message string to NB-IoT.
api.nbSend(addr, port, bufferlen, timeout, type, nownewdatatimeout, rxport)Sends data from the scratchpad buffer (api.nbReceiveBuffer) to NB-IoT.

Info: Maximum length of Rx and Tx messages is 512 bytes. Maximum execution time is limited by timeout in milliseconds.


api.nbSend(addr, port, msg, timeout, type, nownewdatatimeout, rxport)​

api.nbSend("185.8.239.192", 5566, "test message", 6000, "UDP")

Sends a message to an IP address via NB-IoT.

Arguments​

  • addr (string): IP address.
  • port (integer): Port.
  • msg (string): Message to be sent to NB-IoT.
  • timeout (integer): Maximum execution time in milliseconds.
  • type (string): Protocol type:
    • "UDP" - UDP protocol.
    • "TCP" - TCP protocol.
    • "DTLS" - DTLS protocol.

Optional

  • nownewdatatimeout (integer, optional): Maximum delay between data chunks on reception.
  • rxport (integer, optional): Port to use for reception; if not specified, port value is used.

Return​

  • status (integer): Zero for success, negative for failure.
  • rxbuffer (string): Received data or nil for failure.

Example​

-- Sends "test message" string to IP 185.8.239.192 on port 5566 with 6s timeout via UDP
status, answer = api.nbSend("185.8.239.192", 5566, "test message", 6000, "UDP")

--------------------------------

-- Sending IEC readout data via onWake function
function onWake()
	print("Executing OnWake() procedure:")
	RS485ExternalPower(1)
	IECReadoutData = IECReadout(deviceId, initSpeed)
	RS485ExternalPower(0)
	print("Data: ")
	print(IECReadoutData)
	res = api.nbSend(ip, port, IECReadoutData, receiveTimeout, protocol)

api.nbSend(addr, port, bufferlen, timeout, type, nownewdatatimeout, rxport)​

api.nbSend("185.8.239.192", 5566, 128, 6000, "UDP")

Sends a buffer to an IP address via NB-IoT.

Arguments​

  • addr (string): IP address.
  • port (integer): Port.
  • bufferlen (integer): Scratchpad (api.nbReceiveBuffer) buffer is sent in given length.
  • timeout (integer): Maximum execution time in milliseconds.
  • type (string): Protocol type: "UDP", "TCP", or "DTLS".

Optional

  • nownewdatatimeout (integer, optional): Maximum delay between data chunks on reception.
  • rxport (integer, optional): Port to use for reception; if not specified, port value is used.

Return​

  • status (integer): Zero for success, negative for failure.
  • rxbufferlen (integer): Length of the received data, zero for failure.

Example​

-- Send from buffer of length 128 to IP 185.8.239.192 on port 5566 with 6s timeout via UDP
status, rxbufferlen = api.nbSend("185.8.239.192", 5566, 128, 6000, "UDP")

--------------------------------

api.dumpArray(txbuf)
res = api.nbSend(ip, port, txbuf, receiveTimeout, protocol)

api.nbReceiveBuffer()​

Activates, configures, and uses NB-IoT scratchpad buffer.

API NameBrief Description
api.nbReceiveBuffer("activate")Activates the buffer.
api.nbReceiveBuffer("deactivate")Deactivates the buffer.
api.nbReceiveBuffer("dump", size)Dumps content of the buffer.
api.nbReceiveBuffer("set-size", size)Sets the size of the buffer.
api.nbReceiveBuffer("get-size")Gets the size of the buffer.
api.nbReceiveBuffer(start, len, toWrite)Writes data into the buffer at the specified start index.

api.nbReceiveBuffer("activate")​

api.nbReceiveBuffer("activate", wantedIndex)

Activates the buffer.

Arguments​

  • "activate" (string, command)

    ❗command - the argument needs to have this exact form❗

Example​

-- Activate the buffer
api.nbReceiveBuffer("activate")

api.nbReceiveBuffer("deactivate")​

api.nbReceiveBuffer("deactivate")

Deactivates the buffer.

Arguments​

  • "deactivate" (string, command)

    ❗command - the argument needs to have this exact form❗

Example​

-- Deactivate the buffer
api.nbReceiveBuffer("deactivate")

api.nbReceiveBuffer("dump", size)​

api.nbReceiveBuffer("dump", 128)

Dumps content of the buffer.

Arguments​

  • "dump" (string, command)

    ❗command - the argument needs to have this exact form❗

Optional

  • size (integer, optional): Size of the buffer to dump.

Example​

-- Dump the buffer content
api.nbReceiveBuffer("dump", 128)

api.nbReceiveBuffer("set-size", size)​

api.nbReceiveBuffer("set-size", 128)

Sets the size of the buffer.

Arguments​

  • "set-size" (string, command)

    ❗command - the argument needs to have this exact form❗

  • size (integer): Size of the buffer.

Example​

-- Set buffer size to 128
api.nbReceiveBuffer("set-size", 128)

api.nbReceiveBuffer("get-size")​

api.nbReceiveBuffer("get-size")

Sets the size of the buffer.

Arguments​

  • "set-size" (string, command)

    ❗command - the argument needs to have this exact form❗

Example​

api.nbReceiveBuffer("get-size")

api.nbReceiveBuffer(start, len, toWrite)​

api.nbReceiveBuffer(0, 5, "Hello")

Writes data to the NB-IoT scratchpad buffer at the specified start index.

Arguments​

  • start (integer): Index/location where the first byte will be written.
  • len (integer): Length of data to write into the buffer.
  • toWrite (string): Data to write into the buffer.

Return​

  • size (integer): Size of the written data, zero for failure.
  • data (string): Data written into the buffer, empty for failure.

Example​

-- Write "ACRIOS" into the buffer starting at index 0
written, echoed = api.nbReceiveBuffer(0, 6, "ACRIOS")
print("Written bytes:", written)
print("Echoed data:", echoed)

api.nbAT()​

Sends an AT command to NB-IoT module with specified timeout or uses defined commands.

API NameBrief Description
api.nbAT("AT_DEBUG_OFF")Turns OFF printing of AT commands.
api.nbAT("AT_DEBUG_ON")Turns ON printing of AT commands.
api.nbAT("REINITIALIZE")Re-initializes the NB-IoT module.
api.nbAT("ICCID?")Returns ICCID value of current SIM card.
api.nbAT("IMSI?")Returns IMSI value of current SIM card.
api.nbAT("IMEI?")Returns IMEI value of the modem.
api.nbAT("DOWNLINK_MAX_PERIOD", period)Sets maximum period without downlink before re-initializing the module.
api.nbAT("REINIT_HARD_LIMIT_RETRY", retries)Sets number of retries before reset after multiple initializations.
api.nbAT("FORCED_REINIT_DONE?")Monitors if "DOWNLINK_MAX_PERIOD" happened.
api.nbAT("PSM", psmState, edrxState, edrxPeriod, edrxPTW, keepSocketOpen, forceRaiSingleUL, forceRel13, compensateTimeoutForInactTimer)Returns or sets power saving mode network status.
api.nbAT("ON_TAU_EVENT", enable)Enables/disables on TAU event.
api.nbAT("SLEEP_MONITOR", enable)Enables/disables sleep monitor.
api.nbAT("AT_DEBUG_ON_TX")Turns ON printing of AT commands on transmission.
api.nbAT("SET_CEREG_TRESHOLD", threshold)Sets AT+CEREG switch threshold.
api.nbAT("TAU_BLANKING", tau)Sets TAU blanking interval.
api.nbAT("NET_STATUS?")Returns network status.
api.nbAT("RADIO_OFF_SLEEP")Turns OFF radio sleep (PSM).
api.nbAT("UPDATE")Switches to SIM module update mode.
api.nbAT("DTLS", pskid, psk)Changes PSK and PSK ID for DTLS.
api.nbAT("TIME_SYNC", force, zone)Synchronizes time with SIM module.
api.nbAT("TRANSPARENT")Sets transparent mode.
api.nbAT("SLEEP")Puts SIM module to sleep.
api.nbAT("APN=apn")Sets APN.
api.nbAT("PLMNID=plmnid")Sets PLMN ID.
api.nbAT("HARD_RX_TIMEOUT", timeout)Sets hard RX timeout.
api.nbAT(command, timeout, wakeUp, success, err, tryMore, setAwakeBefore, pollBeforeCommand, setAwakeOffAfter, receiveFixedBytes)Sends a custom AT command to the NB-IoT module.

Danger: api.nbAT() is a direct access to the AT command interface of the NB-IoT module. It is advanced and should be used with caution.

Warning: For a backward-compatible interface, avoid using AT commands directly. Instead, use only api.nbSend() for sending.


api.nbAT("AT_DEBUG_OFF")​

api.nbAT("AT_DEBUG_OFF")

Turns OFF printing of AT commands.

Arguments​

  • "AT_DEBUG_OFF" (string, command)

    ❗command - the argument needs to have this exact form❗

Example​

-- Turn off AT debug
api.nbAT("AT_DEBUG_OFF")

api.nbAT("AT_DEBUG_ON")​

api.nbAT("AT_DEBUG_ON")

Turns ON printing of AT commands.

Arguments​

  • "AT_DEBUG_ON" (string, command)

    ❗command - the argument needs to have this exact form❗

Example​

-- Turn on AT debug
api.nbAT("AT_DEBUG_ON")

--------------------------------

if atDebug then
	api.nbAT("AT_DEBUG_ON")
end

api.nbAT("REINITIALIZE")​

api.nbAT("REINITIALIZE")

Re-initializes the NB-IoT module.

Arguments​

  • "REINITIALIZE" (string, command)

    ❗command - the argument needs to have this exact form❗

Example​

-- Re-initialize NB-IoT module
api.nbAT("REINITIALIZE")

--------------------------------

function ns() return api.getTick(2) end

if nextWR == 0 then
	print("BEACON", lBTs, ns())
	lBTs = ns()
else
	print("GATHER", lGTs, ns())
	lGTs = ns()
	if reinitOnWakeGather == 1 then
		api.nbAT("REINITIALIZE")
	end
end

api.nbAT("ICCID?")​

api.nbAT("ICCID?")

Returns ICCID value of current SIM card.

Arguments​

  • "ICCID?" (string, command)

    ❗command - the argument needs to have this exact form❗

Return​

  • iccid (string):
    • "89 88 280 666xxxxxxxx x" (x would be numbers) - ICCID value of current SIM card.
    • "" - empty string for failure.
  • status (integer):
    • 0 - successful identification.
    • -1 - failure to identify.

Example​

-- Get ICCID
iccid, status = api.nbAT("ICCID?")

api.nbAT("IMSI?")​

api.nbAT("IMSI?")

Returns IMSI value of current SIM card.

Arguments​

  • "IMSI?" (string, command)

    ❗command - the argument needs to have this exact form❗

Return​

  • imsi (string):
    • "901 40 51000xxxxx" (x would be numbers) - IMSI value of current SIM card.
    • "" - empty string for failure.
  • status (integer):
    • 0 - successful identification.
    • -1 - failure to identify.

Example​

-- Get IMSI number of SIM card with timeout of 5 seconds
function getIMSI() return imsi or (string.gmatch(api.nbAT("IMSI?", 5000), "([0-9]+)")() or "000000000000000") end

api.nbAT("IMEI?")​

api.nbAT("IMEI?")

Returns IMEI value of the modem.

Arguments​

  • "IMEI?" (string, command)

    ❗command - the argument needs to have this exact form❗

Return​

  • imei (string):
    • "984226666906764" - IMEI value of the modem.
    • "" - empty string for failure.
  • status (integer):
    • 0 - successful identification.
    • -1 - failure to identify.

Example​

-- Get IMEI number of the modem
x = api.nbAT("AT+CGSN")
start = string.find(x, "\n")
finish = string.find(x, "\r", start + 1)
imei = string.sub(x, (start + 1), (finish - 1))
print("IMEI: " .. imei)

api.nbAT("DOWNLINK_MAX_PERIOD", 259200000)

If there is no downlink for the given value, sets timeout to 30 seconds and re-initializes the module.

Arguments​

  • "DOWNLINK_MAX_PERIOD" (string, command)

    ❗command - the argument needs to have this exact form❗

  • period (integer): Maximum period of time in milliseconds (1s is 1000ms) without downlink.

Example​

-- Set downlink max period to 3 days
api.nbAT("DOWNLINK_MAX_PERIOD", 3 * 24 * 3600 * 1000)

api.nbAT("REINIT_HARD_LIMIT_RETRY", retries)​

api.nbAT("REINIT_HARD_LIMIT_RETRY", 5)

If NB-IoT module is initialized the specified number of times in a row, sleeps 4 hours and then resets.

Arguments​

  • "REINIT_HARD_LIMIT_RETRY" (string, command)

    ❗command - the argument needs to have this exact form❗

  • retries (integer): Number of retries before reset.

Example​

-- Set hard limit retry to 5
api.nbAT("REINIT_HARD_LIMIT_RETRY", 5)

api.nbAT("FORCED_REINIT_DONE?")​

api.nbAT("FORCED_REINIT_DONE?")

Monitors if "DOWNLINK_MAX_PERIOD" happened.

Arguments​

  • "FORCED_REINIT_DONE?" (string, command)

    ❗command - the argument needs to have this exact form❗

Return​

  • reinits (integer): Number of re-initializations since reset.

Example​

-- Check if forced reinit done
reinits = api.nbAT("FORCED_REINIT_DONE?")

api.nbAT("PSM", psmState, edrxState, edrxPeriod, edrxPTW, keepSocketOpen, forceRaiSingleUL, forceRel13, compensateTimeoutForInactTimer)​

api.nbAT("PSM", 1, 1, 1024, 64, 1, 0, 0, 0)

Returns or sets power saving mode network status.

Arguments​

  • "PSM" (string, command)

    ❗command - the argument needs to have this exact form❗

Optional

  • psmState (integer): PSM state. Use -1 to skip.
  • edrxState (integer): eDRX state. Use -1 to skip.
  • edrxPeriod (integer): eDRX Requested Value (Period). Use -1 to skip.
  • edrxPTW (integer): eDRX Requested Value (PTW). Use -1 to skip.
  • keepSocketOpen (integer): Keep Socket Open. Use -1 to skip.
  • forceRaiSingleUL (integer): Force RAI Single UL. Use -1 to skip.
  • forceRel13 (integer): Force Rel 13. Use -1 to skip.
  • compensateTimeoutForInactTimer (integer): Compensate Timeout For Inact Timer. Use -1 to skip.

Return​

  • psmState (integer): PSM state.
  • edrxState (integer): eDRX state.
  • edrxPeriod (integer): eDRX Requested Value (Period).
  • edrxPTW (integer): eDRX Requested Value (PTW).
  • keepSocketOpen (integer): Keep Socket Open.
  • forceRaiSingleUL (integer): Force RAI Single UL.
  • forceRel13 (integer): Force Rel 13.
  • compensateTimeoutForInactTimer (integer): Compensate Timeout For Inact Timer.

Example​

-- Set PSM parameters
api.nbAT("PSM", 1, 1, 1024, 64, 1, 0, 0, 0)

api.nbAT("ON_TAU_EVENT", enable)​

api.nbAT("ON_TAU_EVENT", 1)

Enables/disables on TAU event.

Arguments​

  • "ON_TAU_EVENT" (string, command)

    ❗command - the argument needs to have this exact form❗

  • enable (integer):

    • 1 for enable.
    • 0 for disable.

Return​

  • status (integer):
    • 1 for enabled.
    • 0 for disabled.

Example​

-- Enable on TAU event
api.nbAT("ON_TAU_EVENT", 1)

api.nbAT("SLEEP_MONITOR", enable)​

api.nbAT("SLEEP_MONITOR", 1)

Enables/disables sleep monitor.

Arguments​

  • "SLEEP_MONITOR" (string, command)

    ❗command - the argument needs to have this exact form❗

  • enable (integer):

    • 1 for enable.
    • 0 for disable.

Return​

  • status (integer):
    • 1 for enabled.
    • 0 for disabled.
  • timestamp (integer): Last module suspended timestamp.
  • failureCount (integer): Module sleep failure count.

Example​

-- Enable sleep monitor
api.nbAT("SLEEP_MONITOR", 1)

--------------------------------

function onStartup()
	_, FLen = api.wmbusFilter("fetch")
	loadConf()
	print("WMBus-NBIoT, V"..ver)
	hasCC = ex("_hw_features", "CC:1") or false
	api.nbAT("APN=acrios.iot")
	api.nbAT("PLMNID=23003")
	awT = 0
	api.nbAT("ON_TAU_EVENT",1)
	api.nbAT("SLEEP_MONITOR",1)

api.nbAT("AT_DEBUG_ON_TX")​

api.nbAT("AT_DEBUG_ON")

Turns ON printing of AT commands on transmission.

Arguments​

  • "AT_DEBUG_ON_TX" (string, command)

    ❗command - the argument needs to have this exact form❗

Example​

-- Turn on AT debug on TX
api.nbAT("AT_DEBUG_ON_TX")

api.nbAT("SET_CEREG_TRESHOLD", threshold)​

api.nbAT("SET_CEREG_TRESHOLD", 5)

Sets AT+CEREG switch threshold.

Arguments​

  • "SET_CEREG_TRESHOLD" (string, command)

    ❗command - the argument needs to have this exact form❗

  • threshold (integer): AT+CEREG switch threshold.

Example​

-- Set CEREG threshold to 5
api.nbAT("SET_CEREG_TRESHOLD", 5)

api.nbAT("TAU_BLANKING", tau)​

api.nbAT("TAU_BLANKING", 3600)

Sets TAU blanking interval.

Arguments​

  • "TAU_BLANKING" (string, command)

    ❗command - the argument needs to have this exact form❗

  • tau (integer): TAU blanking interval.

Return​

  • interval (integer): TAU blanking interval.

Example​

-- Set TAU blanking to 3600
api.nbAT("TAU_BLANKING", 3600)

api.nbAT("NET_STATUS?")​

api.nbAT("NET_STATUS?")

Returns network status.

Arguments​

  • "NET_STATUS?" (string, command)

    ❗command - the argument needs to have this exact form❗

Return​

  • lastTac (integer): Last TAC.
  • lastCellId (integer): Last Cell ID.
  • lastPeriodicTau (integer): Last Periodic TAU.
  • lastActiveTime (integer): Last Active Time.
  • lastEdrxValue (integer): Last Provided eDRX Value.
  • lastEdrxPtwValue (integer): Last Provided eDRX PTW Value.
  • edrxNegotiated (integer): Negotiated eDRX.
  • timeoutForInactTimer (integer): Compensate Timeout For Inact Timer Value.

Example​

-- Get network status
api.nbAT("NET_STATUS?")

api.nbAT("RADIO_OFF_SLEEP")​

api.nbAT("RADIO_OFF_SLEEP")

Turns OFF radio sleep (PSM).

Arguments​

  • "RADIO_OFF_SLEEP" (string, command)

    ❗command - the argument needs to have this exact form❗

Example​

-- Turn off radio sleep
api.nbAT("RADIO_OFF_SLEEP")

api.nbAT("UPDATE")​

api.nbAT("UPDATE")

Switches to SIM module update mode.

Arguments​

  • "UPDATE" (string, command)

    ❗command - the argument needs to have this exact form❗

Example​

-- Switch to update mode
api.nbAT("UPDATE")

api.nbAT("DTLS", pskid, psk)​

api.nbAT("DTLS", "id", "psk")

Changes PSK and PSK ID for DTLS.

Arguments​

  • "DTLS" (string, command)

    ❗command - the argument needs to have this exact form❗

  • pskid (string):

    • "PSK ID 001 test" - PSK ID.
    • "" - use empty string for deactivation.

  • psk (string):

    • "e560cb0d918d26d31b4f642181f5f570ad89a390931102e5391d08327ba434e9" - PSK ID.
    • "" - use empty string for deactivation.

Return​

  • status (integer):
    • 0 for success.
    • -1 for deactivation.

Example​

-- Set DTLS PSK
api.nbAT("DTLS", "id", "psk")

api.nbAT("TIME_SYNC", force, zone)​

api.nbAT("TIME_SYNC", 1, "UTC")

Synchronizes time with SIM module (by default done automatically on month change).

Arguments​

  • "TIME_SYNC" (string, command)

    ❗command - the argument needs to have this exact form❗

Optional

  • force (integer, optional):
    • 1 for force time sync.
    • 0 for not forcing time sync.
  • zone (string, optional): Time zone:
    • "UTC" for UTC time zone.
    • "LOCAL" for local time zone.

Return​

  • zoneShift (integer): Time zone shift in minutes, returns only when optional argument is set.

Example​

-- Sync time in UTC
api.nbAT("TIME_SYNC", 1, "UTC")

api.nbAT("TRANSPARENT")​

api.nbAT("TRANSPARENT")

Sets transparent mode.

Arguments​

  • "TRANSPARENT" (string, command)

    ❗command - the argument needs to have this exact form❗

Example​

-- Set transparent mode
api.nbAT("TRANSPARENT")

api.nbAT("SLEEP")​

api.nbAT("SLEEP")

Puts SIM module to sleep.

Arguments​

  • "SLEEP" (string, command)

    ❗command - the argument needs to have this exact form❗

Example​

-- Put SIM to sleep
api.nbAT("SLEEP")

api.nbAT("APN=apn")​

api.nbAT("APN=internet")

Sets a custom APN name.

Arguments​

  • "APN=apn" (string, command):

Explanation

The command consists of two parts, first one needs to stay the same:

  • "APN=

Then the string needs to be finnished with a value that represents your APN:

  • myAPN"

Alotgether, it would look like this:

  • "APN=myAPN"

Example​

-- Set APN
api.nbAT("APN=internet")

--------------------------------

function onStartup()
  print("--- NB-IoT - S0 default script ---")
  -- print to serial only when serial is connected
  api.exec("_print_mode", "CONNECTED")
  -- set APN and PLMNID explicitely
  api.nbAT("APN=" .. APN)
  api.nbAT("PLMNID=" .. PLMNID)

api.nbAT("PLMNID=plmnid")​

api.nbAT("PLMNID=20404")

Sets a custom PLMN ID.

Arguments​

  • "PLMNID=plmnid" (string, command):

Explanation

The command consists of two parts, first one needs to stay the same:

  • "PLMNID=

Then the string needs to be finnished with a value that represents your APN:

  • 12345"

Alotgether, it would look like this:

  • "PLMNID=12345"

Example​

-- Set PLMN ID
api.nbAT("PLMNID=20404")

--------------------------------

function onStartup()
  print("--- NB-IoT - S0 default script ---")
  -- print to serial only when serial is connected
  api.exec("_print_mode", "CONNECTED")
  -- set APN and PLMNID explicitely
  api.nbAT("APN=" .. APN)
  api.nbAT("PLMNID=" .. PLMNID)

api.nbAT("HARD_RX_TIMEOUT", timeout)​

api.nbAT("HARD_RX_TIMEOUT", 5000)

Sets hard RX timeout.

Arguments​

  • "HARD_RX_TIMEOUT" (string, command)

    ❗command - the argument needs to have this exact form❗

  • timeout (integer): Hard RX timeout in milliseconds.

Example​

-- Set hard RX timeout to 5000 ms
api.nbAT("HARD_RX_TIMEOUT", 5000)

api.nbAT(command, timeout, wakeUp, success, err, tryMore, setAwakeBefore, pollBeforeCommand, setAwakeOffAfter, receiveFixedBytes)​

api.nbAT("AT+CSQ")

Sends a custom AT command to the NB-IoT module.

Arguments​

  • command (string): AT command.
  • timeout (integer): Maximum execution time in milliseconds.

Optional

  • wakeUp (integer, optional): Sending 1 will make sure that module is not asleep.
  • success (string, optional): Custom success message (default "OK").
  • err (string, optional): Custom error message (default "ERROR").
  • tryMore (integer, optional): Number of retries (max 5, 0 - no answer awaited).
  • setAwakeBefore (integer, optional): Sending 1 will set module awake before command.
  • pollBeforeCommand (integer, optional): Sending 1 will test if module is listening.
  • setAwakeOffAfter (integer, optional): Sending 1 will set module asleep after command.
  • receiveFixedBytes (integer, optional): Number of bytes to receive.

Return​

  • answer (string): nil or non-zero length string with an answer to AT command.
  • status (integer): Zero for success, negative for failure.

Example​

-- Get signal strength
res, b = api.nbAT("AT+CSQ")
print(res)

--------------------------------

else -- beacon
  local function sendBeacon(rcntr, reason, uptime, sinceTau, lastGatherTs, lastBeaconTs, version)
    local ans, res=api.nbAT("AT+CSQ", 6000, nil, "+CSQ:", "99", 3)
    tn=mqtt_topic_base .. "beacon"
    local y, M, d, h, m, sec=api.getTimeDate()
    json("signal", tonumber(string.match(ans, "+CSQ: ([0-9]+),%d.*")) or 0, 1)

--------------------------------

-- Starting MQTT connection
mqtt_server = "server.cz"   -- MQTT server
mqtt_user = "uuuuu"
mqtt_password = "pppppp"
mqtt_port = 1883             -- MQTT port

api.nbAT("AT+CSQ")
api.nbAT("AT+CEREG?")
api.nbAT("AT+COPS?")
-- api.nbAT("AT+CSSLCFG=\"authmode\",0,0") -- ,2 for SSL
api.nbAT("AT+CMQTTSTART", 5000, 0, "+CMQTTSTART: 0") -- Start MQTT
api.nbAT('AT+CMQTTACCQ=0,"' .. getIMSI() .. '"') -- ,1 for SSL
api.nbAT("AT+CMQTTCONNECT=0,\"tcp://" .. mqtt_server .. ":" .. mqtt_port .. "\",60,1,\"" .. mqtt_user .. "\",\"" .. mqtt_password .. "\"", 10000, 0, "+CMQTTCONNECT: 0,0")