Following the same way we did with the MPU6050 article, and the HMC5883L, we now have to design the component BMP180, which is a pressure sensor. Again, instead of drawing the part, you can use SparkFun’s library. Even if you use the component from the library, you can always practice and learn.

The complete list of this series:

First steps

First of all, open the datasheet here. Go to section 6 – “Package”. There you find how the component is, and where is located each pin. All we need to do is to design the footprint according to this drawing.

Open EAGLE, on the main window, left panel, open your library folder. If you configured correctly the library on the first tutorial or you did the second tutorial, you should have a folder! Now select your name on the library panel and go to “File”, then “New” and finally click on “Library”. Before anything, save your file. Go to “File”, “Save as”, and save the file as BMP180 inside your library folder. Great, let’s begin.

Designing the package

Click on the “Package” button and a window will appear. On “New” box, write the package name. This is the name of package size, i.e. for the BMP180 that should be 7 pin LGA, or LGA7. Select “Yes” to create new package with that name. Before drawing the part, go to the “View” menu, then “Grid” and change your units for millimeters, place the “Size” to 1 mm and “Alt” to 0.5mm.

Click on the “Wire” button from the toolbar, select tPlace from the layers menu and draw a rectangle. After that, click on the button and change the properties from the geometric figure to fit on the package size defined by 3.6mm x 3.8mm. This layer will be printed on the PCB, and it helps you when designing the part. If you have any doubt about how to draw the piece, consult the datasheet dimensions. For example, the rectangle will have origin on the coordinate: (0,0), then go to (3.6, 0) to (3.6,3.8) and finally (0,3.8) to (0,0). Your drawing should look like the image.

Now draw the pads. Click on the SMD pad button . Insert one pad anywhere on the screen. Click on the information button again and change its proprieties, like the place and size of it. Put it on the coordinate P1 = (0.35 , 3.4) with size 0.5 x 0.6 mm. However, you can make the pad a little larger than on the datasheet. For example, let’s say 0.7 x 0.9 mm. Now copy that pad with the copy tool . Place all the other 6 terminals around, right clicking it to rotate, when placing the pads on the sides. After that, just position each one on the correct place. It will look like this image.

Now you can draw another line at the top left position to indicate how to mount the component. Click on the name tool and change the pin names for 1 to 7. Beware to put the pin 1 on the upper left pin, and that the pin 7 is on its right side (top view – looking through). At last, select the text button and write “>Name” and “>Value” over the tNames and tValues layers, respectively. OK, your package is ready! Save and get out!

Adjusting the symbols

Now go back to the device creation window. You might need to open your new library file again, and click on the “Device” button. Write it on the “New” dialog box BMP180. Save the file as BMP180. Now this part is easier. The pressure sensor has 7 pins, but only 5 pins are connected. Click on the wire tool and select the Symbols layer. Draw a box of any size you want. After that, select the pin button and place all 7 pins. Remember that you can change the pin size on the top menu, as the image shows. Also, remember to right click when placing the pins if you want to change the side that the pin is. By right-clicking you can rotate it.

After putting the pins, you can name them! Select the name tool once more and name the pins according to the datasheet. Now select the text tool and write “>Name” to the Name layer and “>Value” to the Value layer. Simple as that. There you go! Your schematic should be ready like the image below.


Still, you might notice my pins are noted as “nc”, or “io”, or “pwr”. You are probably thinking I set some configuration to each pin, and you are right. You can click on the correct tool for this, as on the image, and set each pin type. This will help when EAGLE checks the rules from your circuits. For example, the BMP180, if used with I2C should not have pins CSB and SDO connected (this is written on the datasheet). So you can set them as “nc”. If you connect it by mistake, EAGLE will tell you.

Connecting the pieces

Save again your work and you are ready to connect the pins and pads. You can do that by clicking on device the button. Name it BMP180, and create it. First of all, on the new window, click on “Prefix” button (down there) and write a big and capital “U”. Now “OK”. Select the “Add” button and put your new BMP180 you just created. Above the “Prefix”, click on the “New” button and select your LPCC16 package. After all this work, you will see an exclamation mark near the package name. Select the “Connect” button and associate each pin to a pad. Of course, as this pressure sensor has unused pads, some of them won’t be assigned to any pin. There’s no problem on that. However, if this was the opposite, a pin without a pad, you would have problems. The final step is to add a description to your device. Save it and we are done! Cool!

Conclusions

Now we are able to compare our own design with the standard SparkFun library. Putting both components side by side we will see small differences. SparkFun’s design is fancier, although we can still improve our design, and we have larger pads. Cool! Their part follows exactly as described on the datasheet.

Where to go from here

  • Designing The Parts IV (Or Downloading) – PCH8563;
  • Designing The Parts V (Or Downloading) – AT24C64;
  • Schematic I – The Arduino Pro Mini;
  • Schematic II – The Sensors;
  • Schematic III – Other Modules;
  • Board Designing;
  • Generating Files.

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