[sdiy] Using Cortex Mx Arms in Synth DIY

[Eric Brombaugh]

On 12/23/2011 02:58 PM, James Patchell wrote:
>
> The Cortex Mx processors are:
> 1. Very Inexpensive
> 2. Very6 FAST!
> 3. Free Developement Tools?
> 4. Easy to use?
>
> The main problem is the development tools.
>
> NXP has LPCexpresso which has a code size limited compiler (64IK) that
> is basically free. This software is produced by Code Red. For most SDIY
> projects, I bet this would work just fine.
>
> Yagarto is completely free. It is a community supported gcc for the arm
> and right now I believe it works under Windows, Linux and MacOS. It can
> be connected up to Eclipse and provides debugging. Don't really know if
> I would call this easy to use.
>
> Rowley CrossWorks is almost free ($150 for a personal license). Again,
> this is gcc, but comes with a set of much improved libraries and it does
> have a nice user interface (IDE). I have used Rowley to work with Arms
> in the past, however, I don't know if I would call it easy to use.

It's also possible to develop using a stripped-down command-line ARM GCC 
toolchain + text editor + makefiles. If you don't care for top-heavy GUI 
IDEs then this works very well.

> For debugging and programming, JTAG interfaces can range from basically
> free to quite expensive. I have a J-Link that came with an Arm dev kit.
> I*f you buy the JLink by itself, it can be quite pricey. There is an
> open source JTAG interface that uses an FTDI chip. These are fairly
> reasonable, but I don't know how difficult it is to get one to work.

I've used OpenOCD with an Olimex "USB Tiny" JTAG pod (FTDI-based) and 
this works just fine under both Windows and Linux. The Olimex pods are 
kinda pricey ($50 range), especially considering you can get entire 
development systems for less today.

STM32 variants of the Cortex Mx also support a simpler proprietary 
in-system programming interface called SWD which needs only 2 wires + 
ground. The inexpensive (<$20) Discovery development boards can serve as 
programmers for this via either the Windows ST-LINK Utility, or on 
Linux/Mac OS via several open-source downloader/debugger packages.

Eric