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Release v2.2.9: Support for STM8S Access Line Devices

A project log for eForth for cheap STM8S gadgets

Turn cheap stuff from AliExpress into interactive development kits!

Thomas • 04/01/2017 at 12:37•9 Comments

For the STM8 mainstream family *STM8S), ST marketing defined different "classes" of devices:

The code in this project initially targeted the STM8S105C6, but it's now optimized for low-grade Valdue Line devices (the STM8S103F3 is essentially a Value Line device with better specs).

I now have this STM8S105K4T6 devices on my desk:At about $1.90 it offers 16KiB Flash, 2KiB RAM, and 1KiB EEPROM, that's nothing to write home about. However, since the day when I started this project, I had the goal that the code isn't limited to a single STM8 variant. Now I have a target device for testing device configuration.

EDIT1: the code in the develop branch contains the necessary changes for applying STM8EF to Access Line devices. The new include file target.inc also provides board specific configuration options for the memory layout.

EDIT2: I just released v2.2.9 which adds support for Access Line devices. I haven't seen many cheap Access Line gadgets out there, but it's a nice addition to the home-brew toolbox anyway.

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Discussions

K.C. Lee wrote 04/01/2017 at 13:48 • point

Once you pay more than $0.44, might want to look at the STM32F030 as it is much more powerful.  ST has a free license deal with Keil MDK for their STM32F0 line.

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Thomas wrote 04/01/2017 at 16:13 • point

Hi K.C., the STM32F030 is really cool, However, in my career, I spent thousands of hours programming with Keil-C, and I don't miss it much. MECRISP already supports the STM32F0, and there isn't much left to be improved. 

I prommis one thing: once Chinese budget board builders begin bringing better chips on their boards I'll stop bothering everybody with STM8 :-).

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Thomas wrote 04/01/2017 at 16:22 • point

I guess you mean offers like these: http://goo.gl/J94KnB ? Really interesting. It's at least tempting to create a ITC Forth for it (one where practically everything can be exchanged at runtime). I'll keep an eye on it.

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K.C. Lee wrote 04/01/2017 at 21:27 • point

Yes.  I have been using those for a lot of HaD projects before the STM8.  Enough horse power for driving VGA, run real time FFT for audio.  It was cheap enough that I held off for STM8S, but it doesn't have the stories for running at 5V, built-in EEPROM and VUSB (which turns out doesn't work).

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Thomas wrote 04/02/2017 at 06:31 • point

I ordered a set, thanks. Am I right in thinking that the minimal number of external components is just two capacitors and a resistor?
Your VGA terminal shows what's possible with modern components if there is enough dedication to removing waste (muda) from a design.

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K.C. Lee wrote 04/02/2017 at 07:30 • point

If you don't use the bootstrap mode, BOOT0 can be tied to Gnd and save a resistor.  The reset cap might be optional, but recommended.  I haven't tried without one as I sometimes use it to reset other parts e.g. LCD

The brown out is at 2V (max), operating is 2.4V to 3.6V.  From what I have seen, the STM32F050 datasheet power consumption is more accurate.  It is probably a binned part, so they relax on the parameters and not test the other 16K of FLASH.

https://hackaday.io/project/9469/logs

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Thomas wrote 04/02/2017 at 09:01 • point

We've discussed components with "relaxed parameters" parts before. Your findings are very interesting, especially the temperature range observations, which show that these parts provide some headroom for hobby projects!

https://hackaday.io/project/16097-eforth-for-cheap-stm8s-value-line-gadgets/log/51498-whats-the-difference-between-stm8s003f3p-and-stm8s103f3p6#discussion-list

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jaromir.sukuba wrote 04/02/2017 at 16:58 • point

STM32F030 is very likely the same silicon as STM32F050; for now. 

Tomorrow they may change masks to improve process yield and parameters can change, though still within F030 datasheet values.

Datasheets of "higher-end" parts, like F031 could be also useful to guess parameters not mentioned in F030 datasheet. Again, the same applies as per F050.

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K.C. Lee wrote 04/02/2017 at 17:24 • point

The STM32F050 is no longer in their line up.  Judging from the datasheet, they have loosen up the spec for a higher yield already.  On the other hand, it is a 3 years old high volume part, so chances are that it is very well tuned their yields are pretty good and consistent.

Making new masks cost a lot of money, so unless their volume increases to such a point or they have to migrate to new process/geometries, it is unlikely to change in the short term.  There will be other more interesting parts by then. 

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