Re: Lua on Microcontrollers

Hi Bogdan,

On Wed, Dec 11, 2013 at 1:53 AM, Bogdan Marinescu <bogdan.marinescu@gmail.com> wrote:

Hi John,

On Wed, Dec 11, 2013 at 11:37 AM, John Hind <john.hind@zen.co.uk> wrote:

> Date: Tue, 10 Dec 2013 21:09:44 +0200
> From: Bogdan Marinescu <bogdan.marinescu@gmail.com>
> Subject: Re: Lua on Microcontrollers

> About memory, 2M or even 1M of RAM is enough to implement quite a bit
> of functionality with eLua. And there are also MCUs that can work with
> SDRAM
> memory:
>
> http://www.embeddedartists.com/products/boards/lpc4088_qsb.php
>
> That thing has 32M of SDRAM, which is more than enough for any embedded
> Lua application that I can think of.
> And there is also this:
>
> http://am.renesas.com/products/mpumcu/rz/rza/rza1/index.jsp
>
> All in all, internal RAM is evolving in the correct direction for eLua.

Hi Bogdan,

I'd not realised you were still actively developing eLua.

Have you considered a port of eLua onto Raspberry Pi and/or Beaglebone Black? Of course, Lua can easily be installed on these under Linux, but I mean running "bare metal" without an OS. So it would just be a route to getting a low-cost target board with plenty of RAM. The "microcontroller + SDRAM" boards all seem to be very poor value compared to these little Linux boards.

That's true. I've been seriously considering a port to the BBB, since TI provides a framework for writing bare-metal apps on the BBB, but never found the time to do it. When I'm doing now is porting Lua 5.2 on top of the mbed framework (http://www.mbed.org), which has a large range of libraries and a growing platform support. This would allow me to focus on the actual embedded Lua core, without having to worry about porting to a new platform, which is a huge advantage.

The BBB is very interesting; BTW, TI provides the StarterWare framework as part of its push into industrial automation (TI's EtherCAT, PowerLink, Ethernet/IP, and Profibus stacks use it).

On the other hand, for integration I think the SOM (system on module) form factor, such as the Embedded Artists board you linked to, is much easier to deal with than the RPi/Beagle board format.

It's nice to see mbed has taken off; I took a quick glance early on and decided it wasn't interesting to me, but in my plentiful spare time (oops -- which is now less since I did go for a MicroPython board) I'll have to take another look.

Of course if the single chip microcontrollers get up to a few M RAM rather than a few hundred K as at present, the problem would go away, but we do seem to have been waiting a long time for this now.

That's true. I think we're going there, but the wait is not over.

The wait is over if you can spend the money, deal with poor availability, and handle off-chip flash: the Renesas SH7260 has up to 1M SRAM, 0K flash (and they are working on chips with up to 10M SRAM); the ST/Freescale PowerPC-based SPC56xx has 1M SRAM/2M flash, and the Freescale Vybrid (Cortex A5) has 1.5M SRAM/0K flash. For most of these chips, availability is still poor, and prices tend to be high (>$20), but at least all are available in QFP. The Vybrid VF3xx is probably the most interesting: it's ARM-based, the cheapest (~$12 in small volumes), is a 176LQFP, and has an affordable dev board (Phytec's Cosmic board, $55/$65) -- but it's not yet stocked by Mouser or Digikey.

--Tony

The thing I really like about the MicroPython approach is the composite USB device: it presents for development as both a serial console port and a mass storage device. This allows editing of scripts directly on the device from any host computer without having to faf about with file transfer over a serial link.

That's something doable with current eLua, at least on some of the platforms. Shouldn't even be that difficult, some manufacturers provide very good USB libraries.

Best,
Bogdan

- John

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