Updates in ARM Development…
I’ve been pretty busy lately… I recently designed and built my Science Fair project board–I’m still working out all of the bugs in the hardware, but I’m getting there. The project is about embedded networking and encryption on an ARM microcontroller (I chose the Philips LPC2148). I’ll post full details on the project when I’m done with it.
This was my first real PCB. It is almost completely all surface mount, with the exception of a few headers, serial port and stuff like that. The passive component’s size is 0805, which I thought would be a good start with smt. I discovered that smt is awesome. It is much more convenient than through-hole, and you don’t have to reach around and flip the board in all kinds of directions if you need to desolder something.
Since I had little time after developing the schematic in two weeks, I rush designed the board in about 3 days. In the end, not too bad. I chose the wrong component packages for a few things, but I made them fit when I soldered them down. That’s all cosmetics. As for true design mistakes, I shared the TXD0 and RXD0 UART pins of the microcontroller with chip select and interrupt pins on an ethernet controller which happens to hold them high (thus screwing up my uart channel), and I think I messed up the SO/SI - MISO/MOSI lines on the spi. Well, it’s all correctable with wire wrap wire.
Continue reading for more info and cool pictures.
JTAG works great. UART is coming along. It works when the mcu is connected to an external little UART board, but not with the onboard chip and serial port. Soon it should all be fixed.
I got the prototype boards done by Advanced Circuits (http://www.4pcb.com). They shipped the next day, and I had the board about 3 days after I submitting the order. I ordered 3 prototype boards (no soldermask, no silkscreen), and it cost $83 shipped, with UPS 2nd Day. I guess I recommend them, but then again the only other place I’ve tried is SparkFun (now BatchPCB), which took considerably longer (but they cost less for better quality boards). They did a good job too. Advanced Circuits gave me this cool clock-date-temperature-snooze alarm-timer pen/pencil holder thing, the classic promotional post-it pad, and popcorn. Here’s a picture if you don’t believe me:
I soldered everything by hand. I first thought I would need a skillet/hot plate and do some reflow soldering with solder paste, but I changed my mind and I returned the skillet. It actually isn’t that difficult to do by hand at all. I don’t know how I managed to solder the LQFP64 pins for the first time, but things worked out and now I consider SMD is easy.
Here is a picture of the legs of LPC2148. Most of the pins should be down, if not I corrected it at a later time (after the picture was taken).
Finally, I decided to take a quick picture of my electronics setup so far:
Soon I’ll be getting an oscilloscope. Yeah, I’ve been doing all of this stiff the whole time without one. I guess I really don’t need one, but it might help when time is short and I have a big problem. Other than that, I think my setup is pretty complete. Not shown in the picture are my two big green component boxes that store most of my electronics components.
