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Questions relating to designing PCBs
By Zero__
#185632
Hi guys,

I'm designing my first PCB for a big school project and I had a few novice questions. Thanks in advance for the help.

I'm creating a simple breakout board for an XBEE series 1 and an Adafruit bno055 IMU. In the case of the bno055, it's really a breakout board for the breakout board. I want to be able to plug in the Xbee and the Bno055 breakout into my board, and have traces which lead to a six-pin header at the end of the board. That six-pin header will go to six pins on my microcomputer - SDA and SCL (I2C for bno055), RX and TX (UART for Xbee), and Vcc and GND (both of which will be supplied by the microcomputer).

I've been following Sparkfun's Eagle guides and so far, I have made what I believe to be the correct schematic.

http://i.imgur.com/CTruyzU.png?1
Image

I have two questions:
  • Are these individual VCCs and GNDs I have all automatically connected to one another?
  • For the Xbee, what I really want is the header holes for an Xbee series 1. Is placing the Xbee component in my schematic really creating header holes of the proper dimension in my PCB?
  • The bno055 will be a bit more tricky. There is no eagle file for the PCB on the adafruit website. They do, however, have the dimensions for it. I'll have to align the header holes just so, so my bno055 breakout board will fit onto my own PCB. Do I dimension it at the schematic level, or the board layout once I move onto that?
My apologies is these questions are pretty rudimentary and I appreciate the support.
User avatar
By Ross Robotics
#185652
Are these individual VCCs and GNDs I have all automatically connected to one another?
Yes, all VCC connections will be connected and all GND connections will be together.
For the Xbee, what I really want is the header holes for an Xbee series 1. Is placing the Xbee component in my schematic really creating header holes of the proper dimension in my PCB?
Yes, if you are using the correct library. You haven't stated where the library came from, but if it's from Sparkfun, it's correct. Once you create the board in Eagle, you will have a stack of parts that you will place yourself. You will see when you move the Xbee part that it will be 2 headers moving as one.
The bno055 will be a bit more tricky. There is no eagle file for the PCB on the adafruit website. They do, however, have the dimensions for it. I'll have to align the header holes just so, so my bno055 breakout board will fit onto my own PCB. Do I dimension it at the schematic level, or the board layout once I move onto that?
You will have to position the headers vertically 0.7" apart yourself and looks like they are on-grid horizontally. Eagle has a ruler system to make this easier.
By Zero__
#185656
You will have to position the headers vertically 0.7" apart yourself and looks like they are on-grid horizontally. Eagle has a ruler system to make this easier.
Thank you Ross. I think I did just that here: http://i.imgur.com/a0t58tr.png

Do you know how I figure out what diameter those holes need to be though? I will use standard .1" pitch square headers. Those holes on the picture are spaced .1" apart, so pitch should be good.
By davep238
#185678
Zero__ wrote:
You will have to position the headers vertically 0.7" apart yourself and looks like they are on-grid horizontally. Eagle has a ruler system to make this easier.
Thank you Ross. I think I did just that here: http://i.imgur.com/a0t58tr.png

Do you know how I figure out what diameter those holes need to be though? I will use standard .1" pitch square headers. Those holes on the picture are spaced .1" apart, so pitch should be good.
The EAGLE library "pinheader.lbr" uses a 0.04" drill.
By Zero__
#185738
Ok, I've "finished" my first PCB. I'm not sure how much you can tell from a board picture, but I'd like to know if anyone can see any glaring errors. I followed the Sparkfun board tutorial step by step to create it. http://imgur.com/U8NDtXi

One more question: my text is a hard to read grey while in the Sparkfun tutorial, their silkscreen text is white. Did I do something wrong here? I clicked the text tool and selected layer 21, tPlace, as the tutorial said.
By uChip
#185744
Your DOUT signal appears to be shorted to the ground plane. Did you run a DRC? The DRC should catch errors like that.

The color of each layer can be changed. Just click on the "Layer settings..." button or choose the menu View->Layer settings...

- Chip
By Zero__
#185788
Hi,

I'm a little confused by the Sparkfun Board Layout Tutorial when it says: "but adding ground pours to your design at the very beginning (after placing parts, before routing) makes manual routing much easier."

After I add a ground pour, do I not need to worry about routing any of my gnd lines to an actual GND pin because it will automatically be taken care of by the pour?
User avatar
By Ross Robotics
#185791
Zero__ wrote:Hi,After I add a ground pour, do I not need to worry about routing any of my gnd lines to an actual GND pin because it will automatically be taken care of by the pour?
Correct. You can add the ground planes before or after you finish the board. Just don't route the GND and once you hit the ratsnest button, it will connect all of them together. The only exception is when you have "islands". In the attached image, the islands are circled in yellow. You will notice there is a GND via connecting to it to the bottom layer to make the connection. Sometimes you will need to move components around to make the connection.
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