[Oberon] PO2013 - Real time measurement

Chris Burrows chris at cfbsoftware.com
Thu Dec 20 12:00:37 CET 2018

A software solution is fine for a workstation system where it doesn’t need to be too accurate during long-running tasks and can be reset daily. 


However, we find the RTC more convenient to use on Workstation Oberon simply because we don’t have to enter the date and time whenever we restart the system – which can be several times a day during OS development. 


But that was not the main reason behind implementing it. The sort of applications we are targeting are:


1.       Unattended embedded systems

2.       Accurate real-time dataloggers using HCFiler as a high-capacity file system

3.       Running continuously for extended periods e.g.  weeks or months. 


The following features of the Maxim DS3234 Real-time Clock / Calendar device we use make it very suitable for *these* applications: :)


1.       Counts Seconds, Minutes,Hours, Day, Date, Month, and Year with Leap Year Compensation Valid Up to 2099

2.       Battery backup - time is maintained even when the system is powered-down.

3.       ±2 minutes per year accuracy from -40°C to +85°C

4.       Accurate time is maintained during long-running software tasks.





Chris Burrows




From: Jörg [mailto:joerg.straube at iaeth.ch] 
Sent: Thursday, 20 December 2018 3:43 AM
To: chris at cfbsoftware.com; 'ETH Oberon and related systems'
Subject: RE: [Oberon] PO2013 - Real time measurement


I wrote a background task for FPGA Oberon to have a SW-based real time clock.

Accuracy is rather good. I set the time manually, had the system run for a day and the time was still correct 😊




-----Original Message-----
From: Oberon <oberon-bounces at lists.inf.ethz.ch <mailto:oberon-bounces at lists.inf.ethz.ch> > On Behalf Of Chris Burrows
Sent: Wednesday, December 19, 2018 2:07 PM
To: 'ETH Oberon and related systems' <oberon at lists.inf.ethz.ch <mailto:oberon at lists.inf.ethz.ch> >
Subject: Re: [Oberon] PO2013 - Real time measurement


> -----Original Message-----

> From: Oberon [ <mailto:oberon-bounces at lists.inf.ethz.ch> mailto:oberon-bounces at lists.inf.ethz.ch] On Behalf Of 

> Skulski, Wojciech

> Sent: Wednesday, 19 December 2018 3:01 AM

> To: ETH Oberon and related systems

> Subject: Re: [Oberon] PO2013 - Real time measurement


> Chris:


> 1)  Are your examples available for download?



The examples have been written for, and are included with, the various distributions of Astrobe for Cortex-M. e.g. the list here:


 <http://www.astrobe.com/M3Examples/ReadMe.htm> http://www.astrobe.com/M3Examples/ReadMe.htm


However, the SPI Real-time Clock example for FPGA RISC5 Oberon can be downloaded from the FPGA RISC5 section of the Astrobe Forum: 


 <http://www.astrobe.com/forum/viewforum.php?f=13> http://www.astrobe.com/forum/viewforum.php?f=13


I'm planning to upload the I2C temperature sensor example that I tested with the Pepino when Magnus originally wrote the I2C interface a couple of years



 <http://saanlima.com/forum/viewtopic.php?f=14&t=1289> http://saanlima.com/forum/viewtopic.php?f=14&t=1289


However, I'll have to retest it first as there have been a number of significant changes since then.


> 2) Having such components begs a question of system integration.

> Namely, how to add one of these or several to a firmware System On 

> Chip? What are the interfaces? What are the rules? How to add a 

> software driver or drivers after adding the FW components?  The latter 

> mostly means the rules for defining registers and their addresses.



The choice is yours - you are only constrained by how much you can configure the available pins to SPI or I2C functions. Some of the Cortex-M boards and Digilent FPGA boards have a set of Arduino-compatible pins. This has been very convenient for testing the TFT display on various boards as the one I have is mounted on an Arduino Shield.


The PMOD sockets on the Digilent FPGA boards are also very useful and there are a large variety of PMOD-compatible sensors / devices available.


The examples and libraries I supply are intended to be used as components / modules (hardware and software) for prototyping. You can develop and test each part of the system individually. How you eventually integrate them into a system is totally up to you and would depend on how many devices of each type (I2C, SPI, GPIO, ADC etc. etc.) you were using and how many pins you had access to. The FPGA boards are very versatile when it comes to configuring them.





Chris Burrows

CFB Software

 <http://www.astrobe.com> http://www.astrobe.com





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