Netduino 2 and the Adafruit BMP085 Barometer (I2C)

Yes, I'm a noob.  Man, I'm glad I got that off my chest.  

This is the first time I've attempted to hook up a sensor using I2C and I decided to start with this barometer from Adafruit.com: http://www.adafruit.com/products/391

Anyway (11 hours later), what I thought would be simple turned out to be not so simple.  Here is what I am facing.

I have:

- A Netduino 2 running Firmware 4.2.2.1

- A Barometric Pressure sensor from Adafruit (BMP085)  http://www.adafruit.com/products/391  (datasheet: http://www.adafruit....85-DS000-06.pdf)

- A headache

- And the following code:

            byte[] Addr = new byte[2];            Addr[0] = 0xF4;            Addr[1] = 0x34;            byte[] TxBuff = new byte[4];            byte[] RxBuff = new byte[4];            I2CDevice.Configuration I2C_Configuration = new I2CDevice.Configuration(0x77, 400);            I2CDevice I2C1 = new I2CDevice(I2C_Configuration);            I2CDevice.I2CTransaction[] WriteTran = new I2CDevice.I2CTransaction[]             {                I2CDevice.CreateWriteTransaction(Addr),                I2CDevice.CreateWriteTransaction(TxBuff)            };            I2CDevice.I2CTransaction[] ReadTran = new I2CDevice.I2CTransaction[]            {                I2CDevice.CreateWriteTransaction(Addr),                I2CDevice.CreateReadTransaction(RxBuff)            };            while (true)            {                                int iWriteCount = I2C1.Execute(WriteTran, 1000);                Debug.Print("Write Count: " + iWriteCount.ToString());                Thread.Sleep(200);                int iReadCount = I2C1.Execute(ReadTran, 1000);                Debug.Print("Read Count: " + iReadCount.ToString());                string ReadOut = new string(System.Text.Encoding.UTF8.GetChars(RxBuff));                Debug.Print("EEPROM CONTENT:" + ReadOut);                                Thread.Sleep(200);            }

I am starting to wonder if anyone has ever gotten the Netduino 2 and the BMP085 to work over i2c.  Seems to be a weird combination out there on the web.  Hmm.

your code doesent look correct.

also, has your sensor pullups? if not you have to add 4.7kohm ones

ill add my classes, use them, i used it, they work.

...

IC_BMP085 press;

ress = new IC_BMP085(0x77);

...

 void print()   {   String logString =   "pressure: " + press.pressure + " " +   "altitude: " + press.altitude.ToString("F1") + " " +   "free mem: " + Debug.GC(false);   Debug.Print(DateTime.Now + ": " + logString);

}

Okay.  I am going to assume your code is good.  Still returning 0's for all values.

I did not include pull-ups, because I read this one the adafruit product site:

"The sensor is soldered onto a PCB with a 3.3V regulator, I2C level shifter and pull-up resistors on the I2C pins. "

Are you saying I still need to add them anyway?

I will try this regardless, but...  you think it may be a misprint?  That is, did you add them yourself?

Thanks, Noom!  

it really shouldnt return 0's. if it has pullups on their board, than you dont need one.

maybe upgrade the a newer firmware version of your netduino. iirc there were i2c problems before 4.2.2.2

Man, I do not have Windows 7 installed, but I am totally following what you're saying.

Looks like I have some work to do before I can proceed.

You've pointed me in the right direction, NooM!  Thank you!

Okay, I have updated to Windows 7, NETMF 4.3, Visual Studio 2012 and the Netduino Firmware 4.3 Beta.  It didn't make a difference by itself, but then I stumbled upon something that makes no sense.  I'm hoping someone can explain this to me.

Using the code that NooM was nice enough to provide, Visual Studio spit out this in the output window upon the Netduino booting up:

i meant 4.2.2.2 not the 4.3 beta

Hahahahahaha.  WTF did I just do??  

Okay.  This sounds worse than it is.  I will try out 4.2.2.2 on my original development machine and report back.

Thanks!

So, I put everything back the way it was, only updated the firmware to 4.2.2.2.  It actually behaves the same say.  All values report 0 until I disconnect and then reconnect the SDA pin while it's running.

So my last question still stands, I suppose.  Has anyone ever run into this problem?  Any thoughts on what might cause this?

I'm at a total loss, and almost ready to scrap this Netduino.  

Thanks in advance.

damn i thought its fixed in that version

it works fine with netduino v1 versions (iam using the mini, no problems there with i2c,spi and uart, but other bugs )

Hahaha.  You mean an open source platform has other bugs, too??

I do have a Netduino Mini sitting on my shelf that I was going to tackle once I got my feet wet with this, but... Maybe I need to hook up this barometer to the mini to isolate the problem being with the Netduino 2.  At least then I would know.

NooM, do you have or have you ever used a Netduino 2 or +2 with i2c?  I may end up getting another one, but I don't want to go through this again.  I mean, it does work, right?

Considering buying N2P.

I've read some posts here regarding ic2 problems and I have earmarked this particular sensor for use in my first project, so I'm very much interested in following this post.

Will this sensor work for me using ic2? Sensor problem? firmware problem? Platform problem?

@Danger -- could I ask you to be sure to post whether or not you get this problem resolved?

Many thanks and good luck.

no i dont own one, and never have.

but i was active a lot and saw a lot of that i2c stuff, but from what i know it got fixed in 4.2.2.2, well doesent look like

no i dont own one, and never have.

 

but i was active a lot and saw a lot of that i2c stuff, but from what i know it got fixed in 4.2.2.2, well doesent look like

I can confirm the exact same behavior using Adafruit i2c OLED. I have to disconnect / reconnect the SDA pin for it to work properly. I've been fighting this for over an hour now until I ran across this post.

sgraves, you totally did it!  Thanks so much for posting this workaround.

It's totally weird that you have to pull something like this to get it to work right, but... after this many hours of trying stuff, I'll take it!

Thanks, again!

Hi everyone, 

I tried to take a shot at this too. I've got a Netduino Plus 2 too( ), running NETMF4.2.
Borrowing your code I tried it like this:

     public static void NetduinoForumsMethod2()
        {
            IC_BMP085 press;
            press = new IC_BMP085(0x77);
            while (true)
            {


                var logString = "pressure: " + press.pressure + " " + "altitude: " + press.altitude.ToString("F1") + " " + "free mem: " + Debug.GC(false); Debug.Print(DateTime.Now + ": " + logString);
                Thread.Sleep(3000);
            }


        }

In the code class provided, it now crashes on 2 places.
First in the CalculateTemperature method on following line:

                x2 = mc * 2048 / (x1 + md);
                b5 = x1 + x2;


                temperature = (Single)((b5 + 8) >> 4) / 10;

            if (x1 + md == 0)
            {
                temperature = 0;
            }
            else
            {
                x2 = mc * 2048 / (x1 + md);
                b5 = x1 + x2;


                temperature = (Single)((b5 + 8) >> 4) / 10;
            }

            p = (b7 < 0x80000000 ? (b7 * 2) / b4 : (b7 / b4) * 2);

This is caused again by a divided by zero exception, where b4 is 0.

Trying to bypass I tried following code:

            if (b4 == 0) p = 0; //It kept crashing here, /0 doesn't work.
            else p = (b7 < 0x80000000 ? (b7 * 2) / b4 : (b7 / b4) * 2);

And now it is always returning 236

 

06/01/2011 00:05:13: pressure: 236 altitude: 30344.2 free mem: 88488

06/01/2011 00:05:16: pressure: 236 altitude: 30344.2 free mem: 87744

06/01/2011 00:05:19: pressure: 236 altitude: 30344.2 free mem: 87972

06/01/2011 00:05:22: pressure: 236 altitude: 30344.2 free mem: 88716

06/01/2011 00:05:25: pressure: 236 altitude: 30344.2 free mem: 88716

06/01/2011 00:05:28: pressure: 236 altitude: 30344.2 free mem: 88488

 

Problem solving! Many crashes in code that worked with you guys.

So something wrong with my wiring? I just took some pictures of my wiring, hope it helps. 





Only mind the white wires, the other ones are for my OneWire Temperature sensor. (More here)
 

I tried the wiring schema Danger provided: 

Sensor Pin VIn --> Netduino Pin 5V

Sensor Pin GND --> Netduino Pin GND

Sensor Pin SDA --> Netduino Pin SDA

Sensor Pin SCL --> Netduino Pin SCL

But my sensor shows slightly different labels. 

I did it like this:
Sensor VCC => NP2 5V
Sensor GND => NP2 GND

Sensor DA/SDA => NP2 SD
Sensor CL/SCL => NP2 SC

 

Any thing else I could have screwed up? 

 

Thanks in advance!