I have just finished a board in Eagle and would like to get a few opinions.
I have done one pcb before but that is the extent of my experiance.
My first question is how can I post the Eagle or gerber files for view?
A little more info on the project. I am using a microcontroller(Basic Atom) to sample accel, baro , gps and save to SD.
I have done some reading on pcb design but still have some questions.
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What should be done with unconnected pins. Do I configure for output and connect to gnd?
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I used a 2 layer board and a ground plane on bottom. Should I be using a ground plane?
I plan on posting files in a different forum so I will post link here.
mike whorley:
A little more info on the project. I am using a microcontroller(Basic Atom) to sample accel, baro , gps and save to SD.I have done some reading on pcb design but still have some questions.
What should be done with unconnected pins. Do I configure for output and connect to gnd?
I used a 2 layer board and a ground plane on bottom. Should I be using a ground plane?
I plan on posting files in a different forum so I will post link here.
Mike,
Typically when designing a small project, I’ll put the extra pins to a header if I have the space. If I do not, I leave them disconnected.
A ground plane/pour is a good idea. It will keep the grounds at the same potential.
Don’t forget decoupling capacitors for any chips (0.1uF).
It is hard to help much without seeing the board layout. There are many things that a first time designer can do that could cause problems.
James L
A ground plane is always a good idea. If you can’t make it a complete ground plane, them try to minimise the length and number of any tracks on the bottom layer, and try not to have any tracks carrying high speed / fast rise time signals on the top layer pass over the breaks in the ground plane.
I figure configuring unused I/O as an output in firmware is a reasonable idea - you don’t really want floating pins. I must admit that I haven’t always done this, and don’t seem to have problems. Actually, I rarely have unused I/O - there’s always some extra feature that can be added to use up all the pins!
I would also add that you should consider suitable protection / filtering for any pins which are connected to the “outside world”. The real world has ESD, surges / spikes and EMC (susceptibility and emissions) to worry about. Also consider what would happen if someone plugs something in wrong - this could mean reverse polarity protection or polarised connectors etc.
I'd program them as outputs, but would not tie them to ground. I'd run them either to a header or to an uloaded 0805 package so I could use them in the future.. What should be done with unconnected pins. Do I configure for output and connect to gnd?
/mike
n1ist:
I'd program them as outputs, but would not tie them to ground. I'd run them either to a header or to an uloaded 0805 package so I could use them in the future.. What should be done with unconnected pins. Do I configure for output and connect to gnd?
/mike
I figure what Mike meant was configure them as outputs and set the pin state to “0” in firmware.
Good idea to allow the possibility of using the spare pins in the future. Usually I manage to use all of the pins anyway - that typical engineer probllem of feature creep…
MichaelN:
n1ist:
I'd program them as outputs, but would not tie them to ground. I'd run them either to a header or to an uloaded 0805 package so I could use them in the future.. What should be done with unconnected pins. Do I configure for output and connect to gnd?
/mike
I figure what Mike meant was configure them as outputs and set the pin state to “0” in firmware.
Good idea to allow the possibility of using the spare pins in the future. Usually I manage to use all of the pins anyway - that typical engineer probllem of feature creep…
“Feature Creep”…
Ha…you are not the only one.
James L
I have posted pics here http://forums.basicmicro.com/viewtopic.php?f=484&t=9145
I have added headers and jumpers and more headers and still have open pins.
That site requires a login to see the pics - you might consider puting them here too…
Would love to post here but not sure how.
mike whorley:
Would love to post here but not sure how.
I think you must have a place on the net to put them up, then link to them by URL.
James L
Yep, James is correct. You need to upload them to somewhere with an FTP program - I use FileZilla. Your ISP should have given you some free place you can use to store this data.
Then you can link to images with the “Img” button, or put a link using the “URL” button if they are not picture files.