Another thing that i like about the EA LPC4088 board is that it has Xbee formfactor headers on it. EA also makes a GPS accessory that plugs into using the popular PA6H module so there is lots of community support out there for it.
The unit itself is pretty slick and has a 10hz update rate which is helpful for tracking high speed things like race cars. The device talks over a UART using standard NMEA protocol so there are plenty of parsing libraries out there. I literally had this running in a couple hours.
I also soldered on a UFL connector and attached an active external antenna. It has a magnet mount which will work well on the roof of the car.
The precision shown on the display is only enough to get you in my general metro area. The data logger logs six decimal places of info which is more meaningful for tracking a car on track.
This hasn’t yet left my house. I’m super eager to actually drive around with this and see how the data looks. I’m hoping it doesn’t require too elaborate of filtering.
I went around in circles for a few weeks trying to figure out the best way to deal with the main unit. My initial thought was to spin an entirely new PCB to house the LPC4088 Quickstart board, SDcard interface, accelerometer, ADCs, buffer opamps, etc, etc. Basically it would replace the LPC4088 QSB Base Board and add the additional components I needed. Nice and clean.
After thinking a bit, however, I came to the conclusion that this would be pretty redundant, entail a much more complicated design effort, and cost more to build. I might as well use what’s been done for me and simply add what I need. Fortunately, the Base Board has an Arduino shield interface. I can just build a shield! It will plug into the empty shield header interface shown here:
The other benefit of this reduced scope is that I can actually get the design done and built in a timely manner. I decided on using a Microchip 8-channel MP3208 12-bit ADC. This will cover 8 channels of 0-5V analog input, plenty for my logger. I’m using MCP604 opamps and basic RC filters for input buffering/filtering.
Here’s an example of one of the analog input circuits. It has an optional 5V pullup via jumper, buffer, and antialiasing filter.
The other main purpose of the shield is two connectors. One for all my sensors to connect to as inputs and the other to connect to the Remote Display.
The board looks like this:
I just placed the order today so the PCBs should be here in a couple weeks. In the mean time i need to gather up the BOM and order the parts.
In the meantime I plan to focus on the software a bit and get that decent shape. More to come!
I received the “Remote Display” PCBs from OSHPark before Christmas. This was my first time using OSHPark, but i must say it was a pretty great experience. It was very easy to upload my Eagle board design, it processed quickly, and they gave detailed renders of the final boards and all the layers – all easily viewable right on their website. They also arrived ahead of schedule.
I had some time off for the holidays and managed to get one board built up.
It’s funny how I already see things that I wish I had done differently. Why didn’t i label the trim pots and the buttons?!? (The pots control contrast and the R, G, and B backlight). But what matters most came through, it works!
It still looks like a science fair project, but at least all the hardware is set and physically stable. One less bread board to deal with.
Now that this is done I need to focus on both the “Main Unit” PCB and polish up the software.