Sorry if this has been asked elsewhere, but is OneWire support included in 4.2.0 RC1 Scott...

Not entirely sure I understand your question, so I'll try to answer with some observations/facts.

• You must have this native driver to directly communicate with 1-wire devices (parasitic or not) with the Netduino (alternatively, you can use components like those from Peter Anderson)
• With this firmware, I can read from a mix of DS18B20, DS18S20, DS18B20PAR sensors some connected in parasitic mode (only 2 wires - ground and 1-wire signal) and others connected with the 5VDC (non-parasitic). I currently have 5 sensors connected - 3 are not parasitic and 2 are parasitic. That works fine.
• On occassion, I will get a bad read (think 1 in 50 reads) for whatever reason (possibly because I don't have a MOSFET as recommended), but with the CRC check, you always know, so I handle them easily. And usually, it won't happen twice on the same sensor.

-Valkyrie-MT

Valkyrie,

Can you elaborate on the CRC fix you are using to deal with the bad reads? I am getting some bogus temp readings as well..

Scott...

Ok, after a ton of research, and a ton of code tests I figured it out... The DS2450 returns the CRC with the bytes swapped, and it inverts the bits within each byte. i.e. 0xFF = 0x00. The following code results in a good CRC calculation... A little code cleanup and I'm golden! var response = new byte[10]; var status = _core.Read(response); var commandaddrdata = new byte[11]; // Array used to calculate the CRC16 commandaddrdata[0] = 0xAA; commandaddrdata[1] = 0; commandaddrdata[2] = 0; commandaddrdata[3] = response[0]; commandaddrdata[4] = response[1]; commandaddrdata[5] = response[2]; commandaddrdata[6] = response[3]; commandaddrdata[7] = response[4]; commandaddrdata[8] = response[5]; commandaddrdata[9] = response[6]; commandaddrdata[10] = response[7]; UInt32 _LowInt = (UInt32) ~response[8] & 0xFF; // CRC Bits are inverted. Take complement of bits. UInt32 _HighInt = (UInt32) ~response[9] & 0xFF; UInt32 DSCRC16 = (((UInt32)_HighInt << 8) | _LowInt); var crcwithcommand = OneWire.ComputeCRC16(commandaddrdata, count: 11); if (crcwithcommand == DSCRC16) { channelA = (((Int16)response[1] << 8) | response[0]) * ConversionFactor; channelB = (((Int16)response[3] << 8) | response[2]) * ConversionFactor; channelC = (((Int16)response[5] << 8) | response[4]) * ConversionFactor; channelD = (((Int16)response[7] << 8) | response[6]) * ConversionFactor; } else { if (errorProc != null) errorProc(0, "DS2450 CRC Error. Return:" + DSCRC16.ToString() + " Calc:" + crcwithcommand.ToString()); }

Valkyrie,

wondering if you have gotten the CRC code (after an all channel voltage read) working with a DS2450. I know that its a 16 bit CRC, and the datasheet says that its calculated from Command Byte, Address Bytes, and Data Bytes. But I cant get a calculated 16bit CRC that matches the one that is sent back from the 2450. Heres, some test code...

var response = new byte[8];
var res2 = new byte[2];

var commandaddrdata = new byte[11]; // Array used to calculate the CRC16
var status = _core.Read(response); // Data Bytes
var stat2 = _core.Read(res2); // CRC bytes

commandaddrdata[0] = 0xAA;
commandaddrdata[1] = 0;
commandaddrdata[2] = 0;
commandaddrdata[3] = response[0];
commandaddrdata[4] = response[1];
commandaddrdata[5] = response[2];
commandaddrdata[6] = response[3];
commandaddrdata[7] = response[4];
commandaddrdata[8] = response[5];
commandaddrdata[9] = response[6];
commandaddrdata[10] = response[7];

var crc = OneWire.ComputeCRC16(response, count: 8);
var crcwithcommand = OneWire.ComputeCRC16(commandaddrdata, count: 11);

_LowByte = res2[1];
_HighByte = res2[0];
float DSCRC16 = (((UInt16)_HighByte << 8) | _LowByte);

Using this code DSCRC16 never matches crc or crcwithcommand. Have tried it with both inverted and non inverted high and low bytes on the read CRC.

Any ideas?

Thanks,
Scott...

For instance with temperature sensors, I've found that there are 2 kinds of bogus values. Ones corrupted in transmission (will fail CRC) and incomplete calculations from the sensors (which returns a default value that passes CRC). So, what I do is maintain the last sensor value in a variable and give that when requested. While at the same time, I routinely try to update the value. Below is the actual code I use for the sensor read with CRC and uninitialized value checking...

                // Write command and identifier at once
                var matchRom = new byte[9];
                Array.Copy(_rom, 0, matchRom, 1, 8);
                matchRom[0] = OneWire.MatchRom;

                _core.Reset();
                _core.Write(matchRom);
                _core.WriteByte(DS18X20.ReadScratchpad);
                System.Threading.Thread.Sleep(5);  // Wait Tconv (for default 12-bit resolution)

                var response = new byte[9];

                var status = _core.Read(response);
                var CRCPass = OneWire.ComputeCRC(response, count: 8) == response[8];
                var Initialized = OneWireExtensions.BytesToHexString(response.Range(0, 1)) != "0550";

                if (status == 9 && CRCPass && Initialized)
                {
                    if (this.FamilyCode == 0x28)
                    {
                        _lastTemp = ((short)((response[1] << 8) | response[0])) / 16F;
                    }
                    else if (this.FamilyCode == 0x10)
                    {
                        _lastTemp = (float)(((short)((response[1] << 8) | response[0])) >> 1) - 0.25F + ((float)(response[7] - response[6]) / (float)response[7]);
                    }
                    
                    _lastTempTime = DateTime.Now;

                    Debug.Print("Getting DS18X20 Temp - " + this.Address + ", " + _lastTemp.ToString());
                }

Also, the .Range method is just an extension method that returns an arrange of the requested range.

-Valkyrie-MT

FANTASTIC! The One-Wire code in the firmware appears solid to me. I haven't seen any issues with it. Although, I really wanted to see a much simpler and object oriented way of working with 1 wire, so I wrote a wrapper class (called OneWireNetwork) out of CW2's sample. I only tested it with my DS18B20 sensors, but I have more coming soon and hopefully will add classes for them. So, what I did was create a collection class of devices that has a "Discover" method to scan the One-Wire network for devices. I hope this can be the start of a One-Wire framework that will make this the easiest One-Wire platform available. I have attached the code to this post. It is a complete replacement for CW2's OneWireTestApp project from the first post. Also, this example works with 1, 2, 3, or more devices, using parasite power or not.

By using the library, the code gets very simple:

public static void Main()
    {
      // TODO: Change pin according to the actual wiring
      var deviceNetwork = new OneWireNetwork(Pins.GPIO_PIN_D0);
          
      // Interrogate the devices on the network (adding them to the collection)
      deviceNetwork.Discover();

      while (true)
      {
          // Loop through all the discovered devices
          foreach (var aDevice in deviceNetwork)
          {
              Debug.Print("Address: " + aDevice.Address);
              
              if (aDevice is DS18B20) 
                  Debug.Print("Temp: " + (aDevice as DS18B20).Temperature);
          }

          Thread.Sleep(20000);
      }
    }

Output:

1-Wire device present
Multiple devices present
72000002DC320128
B2000002DC405128
54000002DC577D28
Address: 000002DC3201
Temp: 23.375
Address: 000002DC4051
Temp: 23.4375
Address: 000002DC577D
Temp: 23.5
The program '[16] Micro Framework application: Managed' has exited with code 0 (0x0).

Things still to add:
Support for reading and writing to the device memory
Throw Events for device alerts
Robust exception handling
Throw Events for devices being added or removed
Support for a variety of One-Wire devices
Automatic instantiation of classes based on detected device family (should probably use some Reflection here)

I think CW2's firmware should get included into the next Beta. Let's get more people trying to use it...

*** Thanks again to CW2 ***

-Valkyrie-MT

Valkyrie,

I noticed that ever time you call Discover() it causes "foreach (var aDevice in gdeviceNetwork)" to add a new device to gDeviceNetwork...

May be intended, but if you put the discover in a loop, it adds a new device for every 1wire device you have on the network each time you call it. Seems like you should put a CRC check to make sure that the same device is not being added for each call...

FYI: I moved the Discover() call outside the loop, once at the top of Main() and it solved my problem..

Scott...

Sorry for the newb question, but can you tell me where I unzip the files for the example program prior to build and deploy? Firmware installed, just need to know where to put the unziped contents, and the DLL when built. Thanks, Scott...

I'm trying to use the serial port to control a SparkFun serial LCD, and use the OneWire support of this firmware at the same time. I started out using both the DLL included with this release as well as the SerLCD class elsewhere in the forums. When I build either one by themselves, I can either write to the LCD or read 1wire temp sensors, but not both at the same time. I always get an InvalidOperation exception on the serial port open. So, to simplify the equation, I've added the following code to the OneWireTestApp. This just opens the serial port, writes a few lines to it, then starts waiting for button presses to read the temp sensor. I'm getting the same exception on the line lcd.Open(); Anyone else having this problem? public static byte[] getBytes(String message) { System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding(); return encoding.GetBytes(message); } public static void Main() { sw1 = new InterruptPort(Pins.ONBOARD_SW1, true, ResistorModes.Disabled, InterruptModes.InterruptEdgeLow); sw1.OnInterrupt += new NativeEventHandler(sw1_OnInterrupt); // TODO: Change pin according to the actual wiring oneWire = new OneWire(Pins.GPIO_PIN_D0); SerialPort lcd; lcd = new SerialPort(SerialPorts.COM1, 9600, Parity.None, 8, StopBits.One); lcd.ReadTimeout = 10; lcd.Open(); byte[] byteme = getBytes("Welcome to Netduino"); lcd.Write(byteme, 0, byteme.Length); byte[] bytes = new byte[1] { 12 }; lcd.Write(bytes, 0, bytes.Length); Thread.Sleep(Timeout.Infinite); }

IMHO the problem is that your oneWire object uses pin D0 that also has alternative function of being RxD of COM1 and it tries to reserve it during its initialization, which results in exception. To resolve the issue, you can use different pin for OneWire, e.g. D2, or switch to COM2 (D2, D3) for serial communication.

CW2, That did it! Thanks!

Scott...

Darrin, Looking great! Love the e-stop button... Scott...