MiSTer FPGA Forum

Hi Mister People

What's the difference between RTC 1.2 and RTC 1.3?

I've Googled it, with no luck. And I looked at the GitHub page about the RTC board, but that hasn't been updated in two years.

1.3 has solder points for i2c and spi, and traces for a temperature sensor, although there's no current support for the sensor. Other than that, 1.2 and 1.3 are essentially the same

Thanks so much, LegacyPixels.

Some questions for anyone who wants to weigh in:

1. Who decides a) the version numbers, and b) the features that are released in each version? Is there an RTC spec? I couldn't find evidence of one on Google.

2. Is there any practical use, for MiSTer users, of a temperature sensor on a clock? Or for either of the communication protocols mentioned by LegacyPixels? In short, what future functionality does a MiSTer owner sacrifice by buying a 1.2 RTC and foregoing the support for i2c, spi and the temperature sensor present in a version 1.3 RTC?

I didn't realise there were two versions, wonder which I have. Could this mean if a temperature censor was added then we could monitor the temperature of the MiSTer?

Moondandy wrote: ↑Tue May 25, 2021 9:32 am Could this mean if a temperature censor was added then we could monitor the temperature of the MiSTer?

The below is a post from Sorgelig on the old Atari Forums about the temperature sensor:

Source: https://www.atari-forum.com/viewtopic.p ... 70#p345508

Actually, this feature is not even announced. Placement of sensor is not so good as it has no direct contact to FPGA chip. So, the measurement won't reflect actual temperature and will be affected by environment and even airflow direction where sensor will show 20C while real FPGA chip has 70C. Thus it cannot be taken in account when you judge the chip heating.
You need to create a compatible environment to make measurement somehow reflect the actual chip temperature.

So, this whole complexity stops me from offering temperature measurement function. Users will relay on this while it may not reflect the actual temperature.

Xbytez wrote: ↑Wed May 26, 2021 3:30 pm
The below is a post from Sorgelig on the old Atari Forums about the temperature sensor:

Source: https://www.atari-forum.com/viewtopic.p ... 70#p345508

Very helpful. Thank you.

This begs the question: Who decided there needs to be an RTC 1.3, and that a temperature sensor needs to be part of that version?

If Sorgelig has disavowed the usefulness of a temperature sensor on a clock, no less, is there any remaining reason to invest in a version 1.3 RTC that has support for i2c and spi protocols? Or are those equally questionable additions?

[edited to correct a typo]

AnotherGamer wrote: ↑Thu May 27, 2021 10:16 pm

This begs the question: Who decided there needs to be an RTC 1.3, and that a temperature sensor needs to be part of that version?

If Sorgelig has disavowed the usefulness of a temperature sensor on a clock, no less, is there any remaining reason to invest in a version 1.3 RTC that has support for i2c and spi protocols? Or are those equally questionable additions?

There always going to be revisions with this sort of thing. There like 6 different Revisions of the PCB for the MiSTer Analog I/O board, with soldering pads for components that are intentionally left off for features yet to be implemented or abandoned. With even more variants if you look at all the MiSTer add-ons part manufactures/sellers. Not everyone can agree to use 3mm or 5mm LEDs or what size tac switches to use for the User, OSD and Reset buttons. Grey Market Chinese sellers even leave out necessary pins for proper I/O board support.

RTC 1.3 exist as their was an idea to implement a feature later on that turned out to be a dead end, so their pads that remain unpopulated.
It's a common practice with many both consumer and commercial electronics to leave unpopulated pads for features left out for one reason or another.

The NES Toploader for example has though-hole pads for a large capacitor that never got populated.
Turned out Nintendo didn't needed it as it was cheaper for them to revise the AC adapter than to include an additional large power cap in each top loader console.

It would not matter which version of the RTC you get, for us they are functionally the same.

HTTP is a specification. It is managed by the Internet Engineering Task Force. Anyone can go to the IETF website, read the HTTP/2 specification (RFC 7540), and understand exactly what features are defined for that version of the spec.

HTML is a specification. It is managed by the World Wide Web consortium. Anyone can go to w3.org, read the HTML 5 specification, and understand exactly what features are defined for that version of the spec.

When ZeroHimself has RTCs in stock, he sells RTC 1.3.

When misterfpga.co.uk has RTCs in stock, they sell RTC 1.3.

So there's apparently collaboration in this. There's agreement among sellers that there is an RTC "1.3", and agreement on what features must be present in order to label a real-time clock as "1.3".

Who determines those version numbers, and then determines what features are in each version, so that we get the versioning consistency we see between ZeroHimself and MisterFPGA.co.uk?

AnotherGamer wrote: ↑Sat May 29, 2021 3:23 pm Who determines those version numbers, and then determines what features are in each version

Sorgelig

AnotherGamer wrote: ↑Sat May 29, 2021 3:23 pm so that we get the versioning consistency we see between ZeroHimself and MisterFPGA.co.uk?

The designs are open source hardware and anyone is free to manufacture boards Sorgelig has designed and released for the MiSTer project on GitHub, as such this is why you see consistency across vendors.

The MiSTer GitHub for hardware releases is here:

https://github.com/MiSTer-devel/Hardwar ... r/releases

And there's a circuit diagram! Thank you!

So on March 3, 2018 Sorgelig published a circuit diagram for RTC 1.3.

And a little over two months later, on May 17 2018, he declared that a temperate sensor "feature is not even announced".

Is there any reason to wait for an RTC 1.3 to be in stock with, say, ZeroHimself, versus just buying an RTC 1.2 board available right now from MisterAddons?

It seems like RTC 1.3 offers nothing that is immediately or even imminently useful, and that anyone who buys a v1.2 RTC is not missing out on anything at all.

AnotherGamer wrote: ↑Wed Jun 02, 2021 8:05 pm just buying an RTC 1.2 board available right now from MisterAddons?

The picture shown on MisterAddons website is the v1.3 RTC, however in the description it does list the RTC as v1.2

Maybe just send a message to confirm the version actually being sold.

Xbytez wrote: ↑Wed Jun 02, 2021 9:39 pm
The picture shown on MisterAddons website is the v1.3 RTC ...

Very good to know. Thanks a lot.