Content originally posted in LPCWare by markr on Tue Oct 15 13:41:41 MST 2013
I purchased one of the Mini-LPC812 boards from the link above. It took a little longer to arrive than expected because of a Chinese holiday, but the vendor did contact me and let me know it would be slow shipping. I've now had it a coupe days and have been playing with it. My review can be summed up:
[h3]Nice board, bad documentation.[/h3]
It is a small board. I can confirm the headers are 0.1" centers, so it can be used on a breadboard. The board workman ship is good. Is uses all surface mount components and the Rs & Cs are 603s. Header pins for the I/O breakout were not included.
It shipped well packaged with a CD-R with drivers for the USB chip, a copy of Flash Magic, Keil's ARM compiler, NXP docs, and a PDF of the schematic (which has errors). No layout or placement info was included (this will be important later.) The compiler and NXP docs were not current versions.
The USB drivers are required because it uses a SiLabs CP2102 for USB-to-serial instead of the more common FTDI part. The drivers installed without a problem, but require a reboot to work. The schematic shows a voltage regulator from the USB 5.0V to 3.3V, but it is not populated. 3.3V is supplied by the SiLabs part. It can provide 100mA max. The only was to power it externally is to find and cut the trace from the CP2102.
One of the consequences of the size, is the lack of markings. Only a couple parts are marked and the I/O pin markings are on the back of the board. The I/O is a 1:1 match with the LPC812 SO20 pinout, so its not an issue.
The board includes a reset button and a button connected to the ISP pin (P0.1) Other than the LPC812's 20 pins, there are no additional breakout pins. So there is (1) 3.3V pin and (1) GND pin. 5V is not (easily) available, and the only ground point is a single pin. There is an LED to indicate power. The board includes an RGB LED, a micro variable resistor (connected to P0.0) and a SMD 12MHz crystal with padding caps. There is no way to disconnect these devices other than removing them.
The RGB LED is driven directly by 3 I/O pins. There is no transistor buffer, so unless the current limiting resistors are removed, the LED will always present a pull-up load on those pins. [u]The LED pinout is incorrect on the schematic. [/u]The 3 colors are not mapped as shown. This is where the lack of markings and placement documentation became a challenge. Trying to figure out which IO connected to which resistor to which LED took a few minutes with a DVM.
Regarding OpenOCD, there is no JTAG header, although the pins required for SWD could be mapped to a connector, it will not work out of the box and it will not work through the USB header without digging into the SiLabs USB chip and driver. Flash Magic is the only way to program it "as-is". Getting LPCXpresso to produce a HEX file for use with Magic Flash was another project...
Overall, its a nice little board for testing an LPC812 project. The extra components will have to be (delicately) removed to use all the pins and I wish there was the option for external power and another ground pin or 2, but it will do the job. If I wanted more than 2-3 of these, I'd design my own and fix the issue mentioned above.
I'm happy with my $19 investment.
-markr
