[chbot] Help track down a processor - the double chox fish challenge

[Charles Manning]

Yup you'd need huge volumes to make 3c micros work. It might have been less
costly to convince the customer to bin those parts and start again with
something else :-).

At 10k volumes there are quite a few sub-$ STM32s and more from other
vendors. You then have a proper development/debugger set up, proper C,
proper everything.

It stuns me when I see people designing in a PIC16xxx to "save money" or
"reduce power" in a system with a 20k unit lifetime  when there are so many
easier to use options out there that can provide a better result faster.

Now that China has latched on to RISCV in a big mway maybe we'll see a
whole lot of 10 cent RISCV chips in the next few years.


On Thu, Jun 24, 2021 at 6:48 PM Stephen Irons <stephen at irons.nz> wrote:

> Padauk PFS173-S20 is a SOIC-20 and has power on 6 and ground on 15 -- the
> opposite of yours -- and pins 12 and 13 can be an analog input to a
> comparator with an adjustable reference.
>
> Perhaps some of their other series have a different pinout. See
> http://www.padauk.com.tw/en/product/index.aspx
>
> In case you are attracted to 'the 3c microcontroller'
>
>    - C-like language, but really just assembler with some C syntax for
>    loops and conditionals, etc.
>    - No stand-alone command-line compiler, so cannot automate building,
>    etc.
>    - Home-grown IDE with all of the disadvantages of a home-grown IDE.
>    - Windows only tools.
>    - Inaccurate in-circuit emulator. At least they do provide one, but it
>    has significant differences from the real parts. Also, it only works with
>    the low-grade debugger in the home-grown IDE.
>    - Buggy datasheets. They do have errata, but you have to look for
>    them. I see that they now have one dated 2020-06, so perhaps that problem
>    has gone away.
>    - In-circuit programming needs dedicated pins or careful thought as it
>    needs high voltages.
>
> It has an analog comparator, timers and PWM generators, but no other
> peripherals (UART, SPI, I2C, etc). I implemented a bit-banged I2C slave on
> a PFS173-S8 (SOIC-8).
>
> I would not use them again, unless a cost-benefit analysis showed that it
> would be an advantage. You would need significant quantities to offset the
> cost of learning the ins and outs of new tools, new archtecture, etc. Our
> client was hooked by the '3c' bit, and bought all of the (really cheap)
> tools, but failed to appreciate how expensive 3 weeks of debugging might
> be, to find and fix a race condition that happens once per hour on the
> torture test jig, and to radically modify the software when one of the
> external time-constants turned out to be too long for the 8-bit timer, and
> to find out that there was no reliable way to increment on counter overflow
> and not miss I2C events, and so on.
>
> I would use an STM32 or similar for a dollar or two, and get the hardware
> to do stuff that hardware is good at.
>
> Stephen Irons
>
>
> On Wed, Jun 23, 2021 at 13:10, Mark Atherton <markaren1 at xtra.co.nz> wrote:
>
> For those with way too much spare time on their hands. I have a CPU based
> Chinese product which requires some firmware updates (probably a complete
> rewrite). Finding a pin-compatible part with a low cost tool-chain is also
> OK. This is not a commercial exercise. CPU has 20 pins, SOIC package Pin 5
> - I2C Pin 6 - GND Pin 7 - I2C PIN 12 - ADC PIN 13 - ADC PIN 15 - 3V3 Pretty
> much all of the other pins are GPIO. Almost like ATtiny87, except I2C
> required either side of the GND pin. I started by using Digikey as the
> sifting and sorting agent, just wondering if their is a better way. -mark
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