Is it possible to make an mbed "compatible" clone board? I have a couple of LPC1768FBD100 chips here and I am thinking about doing my own pcb for a project but I cant find any firmware on the mbed site and there seems to be a unique serial-no for each mbed. Is this intentional for limiting people to do clones?
Turn your Mbed over and look at the underside. There's a bespoke processor there that's propriety to Mbed. I seriously doubt you will get your hands on one of these chips or the code that runs it. So I reckon a clone is out of the question.
I don't have the forum links handy, but I've seen comments from the mbed team (specifically, in regards to open-sourcing the mbed libraries.) As I understand it, their goal at the current time is to build a solid base platform for prototyping - this is why they haven't released the source for the libraries, becaue they want to avoid fragmentation of the platform. If everyone started modifying the library code, the community would suffer, because it would no longer be possible to have things "just work" - they would rely on a specific version of the library, etc.
So, it stands to reason that they want to avoid hardware clones in the same way. Have you ever looked at the Arduinos? I'm not exaggerating when I say that there's something like 50 "arduino" boards. That was a huge-turn off for me, honestly - so I can understand why they want to avoid it.
Plus, some of the income from the hardware goes to supporting this site, the compiler, etc.
The chip on the underside contains some firmware which handles things like programming the target, serial comms, etc. It also contains the unique serial number which is solely used to allow one user per board to create an mbed.org account.
None of that however prevents you from making a binary compatible board using an LPC1768. In fact, we have step by step instructions for doing just that: http://mbed.org/users/chris/notebook/prototype-to-hardware/
Personally I couldn't be bothered to clone the mbed on it's own. It's a super easy prototyping board to work with. I fully intend to build devices with what will likely amount to something like an mbed surrounded by whatever inputs and outputs I want to use though. When I want to prototype quickly though I will just keep using mbeds. My Arduino has been collecting dust since I got the mbed.
If you are willing to forego the usb flash drive programming, then it could be done. Just wire up the pins of the LPC1768 to a 40-pin socket similarly to the mbed as shown in this schematic
add a USB connector to get 5 volts, convert that to 3.3 volts using a regulator, add all necessary timing crystals (e.g 12 MHz and 32.768 kHz) and break out the serial pins of the mbed using a MAX232 serial converter or similar device to RS232 serial-line drive levels, or you can use a serial-to-USB converter chip (e.g. FT2232 by ftdi). The big benefit of using the FT2232 is you could wire the FT2232 to the JTAG pins to give it built-in JTAG support similar to OpenOCD and the like, and wire the serial port of the FT2232 to the serial port of the LPC1768. Put two push buttons on it, one for reset, and the other for pin P2.10 (for ISP programming). Then you could program it through the serial port using a utility like lpc21isp:
You could also add the DP83848J for ethernet support. If such an mbed clone existed that would be pretty cool, as it would be a all-in-one complete solution for mbed+JTAG+ethernet.
Just dropping a note here in case anyone digs up this thread... look into the LPCXpresso LPC1769 board:
It will run mbed binaries without modification, and for the most part it's pin-compatible with the mbed (has some extra IO pins brought out, as well.) Price is really reasonable too. Not as easy to use as a development board, since it required a cmd-line util to flash it, but for small-batch production purposes where you don't have to reprogram it often, it's quite handy.
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mbed, the fastest way to prototype with ARM based microcontrollers.
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