--- title: "Arduino SNMP Voltage Monitor" url: "https://maker.wiznet.io/jaden/projects/arduino-snmp-voltage-monitor/" markdown_url: "https://maker.wiznet.io/jaden/projects/arduino-snmp-voltage-monitor/md" type: "UCC: User Created Content" author: "41J" author_url: "https://41j.com/blog/2014/12/arduino-snmp-voltage-monitor/" editor: "WIZnet" editor_url: "https://maker.wiznet.io/" original_author: "41J" original_url: "https://41j.com/blog/2014/12/arduino-snmp-voltage-monitor/" published: "2023-03-03" language: "en" likes: 4 views: 328 comments: 0 source: "WIZnet Makers (https://maker.wiznet.io/)" --- # Arduino SNMP Voltage Monitor > Arduino SNMP server Original author: 41J (source: https://41j.com/blog/2014/12/arduino-snmp-voltage-monitor/) ## Article ![](https://maker.wiznet.io/upload/ckeditor5/45786002%5F1677838196%2Epng) using the Arduino with a Wiznet TCP/IP Ethernet chip as a SNMP server to monitor an analog input. The eventual use-case being a battery monitor. Turns out there’s already an SNMP library for the Arduino called [Agentuino](https://code.google.com/p/agentuino/). It hasn’t been updated in a couple of years, but seems to work well. author modified the code to catch the OID associated with UPS battery charge level (1.3.6.1.4.1.318.1.1.1.2.2.1.0). And just return the value of input A0. This can then be read using snmpget (available in the snmp package on Debian): ``` root@navlaptop:/home/new# snmpget -v 1 -r 1 -c public 192.168.2.64 1.3.6.1.4.1.318.1.1.1.2.2.1.0 # NC iso.3.6.1.4.1.318.1.1.1.2.2.1.0 = INTEGER: 78 root@navlaptop:/home/new# snmpget -v 1 -r 1 -c public 192.168.2.64 1.3.6.1.4.1.318.1.1.1.2.2.1.0 # ~ 2.5V iso.3.6.1.4.1.318.1.1.1.2.2.1.0 = INTEGER: 444 root@navlaptop:/home/new# snmpget -v 1 -r 1 -c public 192.168.2.64 1.3.6.1.4.1.318.1.1.1.2.2.1.0 #NC iso.3.6.1.4.1.318.1.1.1.2.2.1.0 = INTEGER: 88 ``` So the setup appears to work quite well. One concern is the power concumption which with the Arduino and Wiznet is around 170mA. This might not be suitable for the solar deployment I’ve been looking at. Anyway the code is below (it’s just a modified version of the Agentuino sample): `/**` `* Agentuino SNMP Agent Library Prototyping...` `*` `* Copyright 2010 Eric C. Gionet ` `*` `*/` `#include // Include the Streaming library` `#include // Include the Ethernet library` `#include ` `#include ` `#include ` `#include ` `//` `#define DEBUG` `//` `static` `byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };` `static` `byte ip[] = { 192, 168, 2, 64 };` `static` `byte gateway[] = { 192, 168, 2, 1 };` `static` `byte subnet[] = { 255, 255, 255, 0 };` `//` `// tkmib - linux mib browser` `//` `// RFC1213-MIB OIDs` `// .iso (.1)` `// .iso.org (.1.3)` `// .iso.org.dod (.1.3.6)` `// .iso.org.dod.internet (.1.3.6.1)` `// .iso.org.dod.internet.mgmt (.1.3.6.1.2)` `// .iso.org.dod.internet.mgmt.mib-2 (.1.3.6.1.2.1)` `// .iso.org.dod.internet.mgmt.mib-2.system (.1.3.6.1.2.1.1)` `// .iso.org.dod.internet.mgmt.mib-2.system.sysDescr (.1.3.6.1.2.1.1.1)` `const` `static` `char` `sysDescr[] PROGMEM = ``"1.3.6.1.2.1.1.1.0"``; ``// read-only (DisplayString)` `// .iso.org.dod.internet.mgmt.mib-2.system.sysObjectID (.1.3.6.1.2.1.1.2)` `const` `static` `char` `sysObjectID[] PROGMEM = ``"1.3.6.1.2.1.1.2.0"``; ``// read-only (ObjectIdentifier)` `// .iso.org.dod.internet.mgmt.mib-2.system.sysUpTime (.1.3.6.1.2.1.1.3)` `const` `static` `char` `sysUpTime[] PROGMEM = ``"1.3.6.1.2.1.1.3.0"``; ``// read-only (TimeTicks)` `// .iso.org.dod.internet.mgmt.mib-2.system.sysContact (.1.3.6.1.2.1.1.4)` `const` `static` `char` `sysContact[] PROGMEM = ``"1.3.6.1.2.1.1.4.0"``; ``// read-write (DisplayString)` `// .iso.org.dod.internet.mgmt.mib-2.system.sysName (.1.3.6.1.2.1.1.5)` `const` `static` `char` `sysName[] PROGMEM = ``"1.3.6.1.2.1.1.5.0"``; ``// read-write (DisplayString)` `// .iso.org.dod.internet.mgmt.mib-2.system.sysLocation (.1.3.6.1.2.1.1.6)` `const` `static` `char` `sysLocation[] PROGMEM = ``"1.3.6.1.2.1.1.6.0"``; ``// read-write (DisplayString)` `// .iso.org.dod.internet.mgmt.mib-2.system.sysServices (.1.3.6.1.2.1.1.7)` `const` `static` `char` `sysServices[] PROGMEM = ``"1.3.6.1.2.1.1.7.0"``; ``// read-only (Integer)` `// .1.3.6.1.4.1.318.1.1.1.2.2.1.0` `const` `static` `char` `upsBatPnct[] PROGMEM = ``"1.3.6.1.4.1.318.1.1.1.2.2.1.0"``;` `//` `// Arduino defined OIDs` `// .iso.org.dod.internet.private (.1.3.6.1.4)` `// .iso.org.dod.internet.private.enterprises (.1.3.6.1.4.1)` `// .iso.org.dod.internet.private.enterprises.arduino (.1.3.6.1.4.1.36582)` `//` `//` `// RFC1213 local values` `static` `char` `locDescr[] = ``"Agentuino, a light-weight SNMP Agent."``; ``// read-only (static)` `static` `char` `locObjectID[] = ``"1.3.6.1.3.2009.0"``; ``// read-only (static)` `static` `uint32_t` `locUpTime = 0; ``// read-only (static)` `static` `char` `locContact[20] = ``"Eric Gionet"``; ``// should be stored/read from EEPROM - read/write (not done for simplicity)` `static` `char` `locName[20] = ``"Agentuino"``; ``// should be stored/read from EEPROM - read/write (not done for simplicity)` `static` `char` `locLocation[20] = ``"Nova Scotia, CA"``; ``// should be stored/read from EEPROM - read/write (not done for simplicity)` `static` `int32_t` `locServices = 7; ``// read-only (static)` `uint32_t` `prevMillis = millis();` `char` `oid[SNMP_MAX_OID_LEN];` `SNMP_API_STAT_CODES api_status;` `SNMP_ERR_CODES status;` `void` `pduReceived()` `{` `SNMP_PDU pdu;` `//` `#ifdef DEBUG` `Serial << F(``"UDP Packet Received Start.."``) << F(``" RAM:"``) << freeMemory() << endl;` `#endif` `//` `api_status = Agentuino.requestPdu(&pdu);` `//` `if` `( pdu.type == SNMP_PDU_GET || pdu.type == SNMP_PDU_GET_NEXT || pdu.type == SNMP_PDU_SET` `&& pdu.error == SNMP_ERR_NO_ERROR && api_status == SNMP_API_STAT_SUCCESS ) {` `//` `pdu.OID.toString(oid);` `//` `//Serial << "OID: " << oid << endl;` `//` `if` `( strcmp_P(oid, sysDescr ) == 0 ) {` `// handle sysDescr (set/get) requests` `if` `( pdu.type == SNMP_PDU_SET ) {` `// response packet from set-request - object is read-only` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = SNMP_ERR_READ_ONLY;` `} ``else` `{` `// response packet from get-request - locDescr` `status = pdu.VALUE.encode(SNMP_SYNTAX_OCTETS, locDescr);` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = status;` `}` `//` `#ifdef DEBUG` `Serial << F(``"sysDescr..."``) << locDescr << F(``" "``) << pdu.VALUE.size << endl;` `#endif` `} ``else` `if` `( strcmp_P(oid, sysUpTime ) == 0 ) {` `// handle sysName (set/get) requests` `if` `( pdu.type == SNMP_PDU_SET ) {` `// response packet from set-request - object is read-only` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = SNMP_ERR_READ_ONLY;` `} ``else` `{` `// response packet from get-request - locUpTime` `status = pdu.VALUE.encode(SNMP_SYNTAX_TIME_TICKS, locUpTime);` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = status;` `}` `//` `#ifdef DEBUG` `Serial << F(``"sysUpTime..."``) << locUpTime << F(``" "``) << pdu.VALUE.size << endl;` `#endif` `} ``else` `if` `( strcmp_P(oid, sysName ) == 0 ) {` `// handle sysName (set/get) requests` `if` `( pdu.type == SNMP_PDU_SET ) {` `// response packet from set-request - object is read/write` `status = pdu.VALUE.decode(locName, ``strlen``(locName));` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = status;` `} ``else` `{` `// response packet from get-request - locName` `status = pdu.VALUE.encode(SNMP_SYNTAX_OCTETS, locName);` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = status;` `}` `//` `#ifdef DEBUG` `Serial << F(``"sysName..."``) << locName << F(``" "``) << pdu.VALUE.size << endl;` `#endif` `} ``else` `if` `( strcmp_P(oid, sysContact ) == 0 ) {` `// handle sysContact (set/get) requests` `if` `( pdu.type == SNMP_PDU_SET ) {` `// response packet from set-request - object is read/write` `status = pdu.VALUE.decode(locContact, ``strlen``(locContact));` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = status;` `} ``else` `{` `// response packet from get-request - locContact` `status = pdu.VALUE.encode(SNMP_SYNTAX_OCTETS, locContact);` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = status;` `}` `//` `#ifdef DEBUG` `Serial << F(``"sysContact..."``) << locContact << F(``" "``) << pdu.VALUE.size << endl;` `#endif` `} ``else` `if` `( strcmp_P(oid, sysLocation ) == 0 ) {` `// handle sysLocation (set/get) requests` `if` `( pdu.type == SNMP_PDU_SET ) {` `// response packet from set-request - object is read/write` `status = pdu.VALUE.decode(locLocation, ``strlen``(locLocation));` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = status;` `} ``else` `{` `// response packet from get-request - locLocation` `status = pdu.VALUE.encode(SNMP_SYNTAX_OCTETS, locLocation);` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = status;` `}` `//` `#ifdef DEBUG` `Serial << F(``"sysLocation..."``) << locLocation << F(``" "``) << pdu.VALUE.size << endl;` `#endif` `} ``else` `if` `( strcmp_P(oid, sysServices) == 0 ) {` `// handle sysServices (set/get) requests` `if` `( pdu.type == SNMP_PDU_SET ) {` `// response packet from set-request - object is read-only` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = SNMP_ERR_READ_ONLY;` `} ``else` `{` `// response packet from get-request - locServices` `status = pdu.VALUE.encode(SNMP_SYNTAX_INT, locServices);` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = status;` `}` `//` `#ifdef DEBUG` `Serial << F(``"locServices..."``) << locServices << F(``" "``) << pdu.VALUE.size << endl;` `#endif` `} ``else` `if` `( strcmp_P(oid, upsBatPnct) == 0) {` `// battery voltage output` `int` `val = analogRead(0);` `status = pdu.VALUE.encode(SNMP_SYNTAX_INT, val);` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = status; ` `}` `else` `{` `// oid does not exist` `//` `// response packet - object not found` `pdu.type = SNMP_PDU_RESPONSE;` `pdu.error = SNMP_ERR_NO_SUCH_NAME;` `}` `//` `Agentuino.responsePdu(&pdu);` `}` `//` `Agentuino.freePdu(&pdu);` `//` `//Serial << "UDP Packet Received End.." << " RAM:" << freeMemory() << endl;` `}` `void` `setup()` `{` `Serial.begin(9600);` `Ethernet.begin(mac, ip);` `//` `api_status = Agentuino.begin();` `//` `if` `( api_status == SNMP_API_STAT_SUCCESS ) {` `//` `Agentuino.onPduReceive(pduReceived);` `//` `delay(10);` `//` `Serial << F(``"SNMP Agent Initalized..."``) << endl;` `//` `return``;` `}` `//` `delay(10);` `//` `Serial << F(``"SNMP Agent Initalization Problem..."``) << status << endl;` `}` `void` `loop()` `{` `// listen/handle for incoming SNMP requests` `Agentuino.listen();` `//` `// sysUpTime - The time (in hundredths of a second) since` `// the network management portion of the system was last` `// re-initialized.` `if` `( millis() - prevMillis > 1000 ) {` `// increment previous milliseconds` `prevMillis += 1000;` `//` `// increment up-time counter` `locUpTime += 100;` `}` `}` --- Source: https://maker.wiznet.io/jaden/projects/arduino-snmp-voltage-monitor/