41J Blog

I’ve been looking at a Par can (Parabolic aluminized reflector light) lighting chassis with a view to designing a LED PCB to sit inside it. I believe the model I have is a PAR64 it’s sold by Sound House here in Japan, but I believe it’s pretty much standard.

Normally the PAR64 takes bulbs with integrated parabolic reflectors like these:

I’m interested in installing LEDs in the base, here are the base dimensions:

I’m also considering how a PCB might be mounted into the base, I’ve been looking at these angle brackets. And possibly drilling some holes in the chassis:

So, I’m still considering the feasibility of the project. It seems like a parabolic mirror might be required which would be somewhat limiting. However I’m hoping there are other novel options.

As a quick proof of concept I wanted to try 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. It hasn’t been updated in a couple of years, but seems to work well. I installed the library and 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). I then 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 <[email protected]>
*
*/
#include <Streaming.h>         // Include the Streaming library
#include <Ethernet.h>          // Include the Ethernet library
#include <SPI.h>
#include <MemoryFree.h>
#include <Agentuino.h> 
#include <Flash.h>
//
#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;
  }
}

Arduino SNMP:
https://code.google.com/p/agentuino/

Arduino SNMP Temp:
http://openhardware.gridshield.net/home/arduino-snmp-temperature-sensor

Today we’ve been playing around with some ESP8266 boards. This IC uses a lx106 32bit core, running at 80MHz, and have ~80K of RAM and use serial EEPROM which is generally around 512Kb. They also have an integrated Wifi RF frontend.

We used the toolchain available here to get the boards programmed.

The boards can be programmed using 3.3V RS232 signals, so a basic FTDI USB adapter works well.

When programming pins 3 and 4 need to held high. Pin 5 should be held low. I built a board to tie these pins to the correct values, as a programming interface between the FTDI board and the ESP8266 as follows:

Prog board 1:

Prog board 2:

Prog board 3:

Prog board 4:

While you can use this board of programming, the pins should not be pulled up/down on board. The ESP8266 can also require upto 1A when running with the Wifi up. On my tests I also tied pin 4 and 6 high in the running configuration (however I’m not sure if this is actually required) anyway, I built up these boards for the running config:

Power board front:

Power board back:

I flashed the device with the blinky demo from the Toolchain examples, however the LED on our boards is not connected to GPIO2 (which the demo uses). However the output was easily visible on a scope:

Scope output:

Resources

Pinout:

Wiki page with a bunch of useful info: here
Core Datasheet with instruction set etc: here
Core Marketing summary: here
IC Datasheet: here

Random notes:

Also need:

apt-get install gperf
apt-get install bison

Update path:

PATH=$PATH:/opt/Espressif/crosstool-NG/builds/xtensa-lx106-elf/bin
PATH=$PWD/builds/xtensa-lx106-elf/bin:$PATH

I previously posted a quick example of using the standard library websockets API in golang. Unfortunately there are a number of issues that make difficult to use in practice. Notably, it lacks support for PING/PONG packets which are often used to for KeepAlive functionality in websockets. This is particularly important, as browsers tend to be aggressive in killing off these connections.

So, here’s a quick complete example of Gorilla Websockets in golang, with similar functionality to that I posted previously. It simply echos everything it receives back to the client. First the golang code:

package main

import (
        "github.com/gorilla/websocket"
        "net/http"
        "fmt"
)

var upgrader = websocket.Upgrader{
    ReadBufferSize:  1024,
    WriteBufferSize: 1024,
}

func print_binary(s []byte) {
  fmt.Printf("Received b:");
  for n := 0;n < len(s);n++ {
    fmt.Printf("%d,",s[n]);
  }
  fmt.Printf("\n");
}

func echoHandler(w http.ResponseWriter, r *http.Request) {
    conn, err := upgrader.Upgrade(w, r, nil)
    if err != nil {
        //log.Println(err)
        return
    }

    for {
        messageType, p, err := conn.ReadMessage()
        if err != nil {
            return
        }

        print_binary(p)

        err = conn.WriteMessage(messageType, p);
        if  err != nil {
            return
        }
    }
}

func main() {
  http.HandleFunc("/echo", echoHandler)
  http.Handle("/", http.FileServer(http.Dir(".")))
  err := http.ListenAndServe(":8080", nil)
  if err != nil {
    panic("Error: " + err.Error())
  }
}

And then the html used to interface with the websocket. Save it in the same directory as the golang program, and access it at: http://localhost:8080/filename.html

<html>
<head>
<meta charset="UTF-8" />
<script>
        var serversocket = new WebSocket("ws://localhost:8080/echo");

        serversocket.onopen = function() {
                serversocket.send("Connection init");
        }

        // Write message on receive
        serversocket.onmessage = function(e) {
                document.getElementById('comms').innerHTML += "Received: " + e.data + "<br>";
        };

        function senddata() {
                var data = document.getElementById('sendtext').value;
                serversocket.send(data);
                document.getElementById('comms').innerHTML += "Sent: " + data + "<br>";
        }

</script>
</head>

<body>
        <input id="sendtext" type="text" />
        <input type="button" id="sendBtn" value="send" onclick="senddata()"></input>
        <div id='comms'></div>
</body>
</html>