April 2018 - Oberon - mailman3.inf.ethz.ch

FPGA - nRF24L01 `RPI Net' server
by Tomas Kral 23 Apr '18

23 Apr '18

Hi, I have wanted to do `network time client' exercise by Paul Reed, left on hold since last year, but ended up coding simple `Net' server, supporting only subset of messages, those needed to set Oberon time. Executing `Net.GetTime RPI ~' does things and sets time picked from RPI, good. I dump packet headers, as it is interesting to follow packet exchange, also for debugging. Output below [Ctrl-C to exit]: valid header 52 4 54 255 name request RPI 53 0 79 54 RPI set valid header 70 0 54 79 time request 71 4 79 54 ^C Now I need someone to click regularly on `Net.GetTime RPI ~' for me, to keep my Oberon time in sync :-) I wonder if it makes sense to implement full net server? Code skeleton below. while(true) { receivehead( &head1 ); if ( head1.valid ) { cout << "valid header \n"; printf ("%d %d %d %d\n", head1.typ, head1.len, head1.sadr, head1.dadr); switch ( head1.typ ) { case NRQ: cout << "name request\n"; i = 0; do { receive(&x); id[i++] = x; if (i == 7) { id[7] = 0; x = 0; }; } while ( x != 0 ); while ( i++ < head1.len ) receive(&x); printf ( "%s\n", id ); if ( strcmp( id, "RPI" ) == 0 ) { setpartner( id ); send( NRS, 0, dmy ); printf( "%s set\n", partner ); }; break; case TRQ: cout << "time request\n"; uxobtime(&obtime); i = 0; appendw( obtime, idb, 4, &i ); send( TIM, 4, idb ); break; default: cout << "skipped\n"; skip ( head1.len ); break; }; } delay(1); } -- Tomas Kral <thomas.kral(a)email.cz>

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FPGA - nRF24L01 connection
by Tomas Kral 18 Apr '18

18 Apr '18

Hi, As advised by Paul, I have tried carrier test example, as I am still unable ping payloads between RPI and Oberon. On RPI, I run a simple example `RF24' program, it steps through all 126 channels, and listens for 128us in each, incrementing carrier count if detected any on that channel. On Oberon I just execute `NRF.Ping' command, that just tries to send 32 byte payload over the wireless. Carriers detected in channels, are reported as a single hex digit From left to right, 0..126 On channel 5, SW := {1,0,0,0,0,0,0,0}; 000033400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 000022300000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 0000123000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000000000000000000000000000000 On channel 85, SW := {1,1,1,0,0,0,0,0}; 000000000000000000000000000000000000000000000000000000000000000000000000000000000000321000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000000123000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000000435000000000000000000000000000000000000000 I am surprised to see that signal carrier is detected in the spectrum of channels, 4,5,6 and 84,85,86 with similar count??? Many thanks for any insight. -- Tomas Kral <thomas.kral(a)email.cz>

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FPGA - User/Password
by Tomas Kral 18 Apr '18

18 Apr '18

Hi, `Oberon.Mod' defines station Username and Password, `Net.Mod' makes use of it when establishing connection to other machines. What is the command to set user credentials, PO2013 book mentions user initials are typically used as station names? Many thanks. -- Tomas Kral <thomas.kral(a)email.cz>

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FPGA - User/Password
by Andreas Pirklbauer 17 Apr '18

17 Apr '18

> > What is the command to set user credentials, PO2013 book > > mentions user initials are typically used as station names? > > System.SetUser username password ~ PS: In fact, you just execute ‘System.SetUser’ and then enter the username and password on the keyboard.

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FPGA - User/Password
by Andreas Pirklbauer 17 Apr '18

17 Apr '18

> What is the command to set user credentials, PO2013 book > mentions user initials are typically used as station names? System.SetUser username password ~

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Re: [Oberon] ABSTRACT to EMPTY redefinition in Component Pascal
by Josef Templ 16 Apr '18

16 Apr '18

> > I thought that It could be used to have (a sort of) multiple interfaces, > grouping all the methods as abstract in the the base record and selecting > only those that are needed in later extensions. > > For example a Stream class may have all the (stream related) methods as > abstract, while non-buffered extensions redefine flush() as EMPTY. > However not all streams have positioning, but I can't redefine tell() as > EMPTY since it returns something. > > So it looked like rather limiting. > > -- > Diego Sardina > > I think of EMPTY as a short-hand notation for BEGIN END ProcName; In principle, it would allow the compiler to save a few bytes and use a generic stub for the return code, but only if such a generic stub is possible on a particular target platform. This depends on the details of managing the run-time stack. The i386 code generator is not using a generic sub. In addition, the compiler puts a flag into the symbol file that marks an exported EMPTY procedure. This is used for checking if a super call to an EMPTY procedure is made. Super calls are not allowed for EMPTY procedures. I am not sure why. It may be because it does not give sense to call something that does nothing by definition. But this is disputable, I think. It breaks the abstraction in the sense that it tells you something about the (missing) implementation of a procedure. In general, I am not aware of any other major OOP language that has a similar concept. It does not seem to be very important, and, yes, it is rather limited. - Josef

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Re: ABSTRACT to EMPTY redefinition in Component Pascal
by Josef Templ 15 Apr '18

15 Apr '18

In practice, I think, there are not too many use cases for overriding an ABSTRACT method by an EMPTY method but it is possible to think of the following situation: An ABSTRACT base type *Object *provides ABSTRACT methods *Store* and *Load* for persisting the contents of an object. A concrete sub-type must implement all methods but if there is nothing to store resp. load, the implementation of *Store *and *Load *could be simply marked EMPTY. Note: In reality, storing and loading objects is usually more complicated and an EMPTY implementation may not be a good solution. For example, a version tag per extension level may be required for keeping persisted objects compatible when the storage format or contents changes in later versions. In BlackBox this approach is used throughout the framework. See module *Stores*. - Josef

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FPGA - nRF24L01 connection
by Tomas Kral 12 Apr '18

12 Apr '18

Hi, I have two Nordic wireless modules. I have wired one of them to my RPI, see photo, the other should plug into Pepino Oberon FPGA board. I have also compiled a gateway from `MySensors' git repo. Running the gateway gives following. ... Protocol version - 1.4 Created PTY '/dev/pts/2' Gateway tty: /dev/ttyMySensorsGateway ================ SPI Configuration ================ CSN Pin = CE0 (PI Hardware Driven) CE Pin = Custom GPIO25 Clock Speed = 8 Mhz ================ NRF Configuration ================ ... When I use a serial cable over USB (FTDI), I just access serial as /dev/ttyUSB1 device, and I use PCLink at Oberon end. But, how do I exchange data with Oberon over wireless, what is the gateway device, do I need to modify RF24.Mod? Many thanks in advance. -- Tomas Kral <thomas.kral(a)email.cz>

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Re: [Oberon] Re (2): Class Methods Vs. Procedure variables in Records
by peter＠easthope.ca 11 Apr '18

11 Apr '18

From: Andreas Pirklbauer <andreas_pirklbauer(a)yahoo.com> Date: Sun, 2 Jul 2017 13:09:01 +0000 > I have not checked, but how does one upload something to the > Wikibook? Copy & paste via the system clipboard. For instructions about editing & etc. click on the Help link in the left margin. https://en.wikibooks.org/wiki/Help:Contents > Who maintains it? Question 6 in the FAQ. https://en.wikibooks.org/wiki/Help:FAQ/Overview > What is its goal? For Wikibooks in general, see FAQ question 2. https://en.wikibooks.org/wiki/Help:FAQ/Overview The Oberon Wikibook aims to document details too involved for the Wikipedia article. https://en.wikipedia.org/wiki/Oberon_(operating_system) Ref. 1st sentence below the title. https://en.wikibooks.org/wiki/Oberon Regards, ... Lyle E. -- This message was composed and transmitted by software designed to avoid the need, overhead and vulnerability of antivirus software. 123456789 123456789 123456789 123456789 123456789 123456789 123456789 Tel: +1 360 639 0202 Pender Is.: +1 250 629 3757 http://easthope.ca/Peter.html Bcc: peter at easthope. ca

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ABSTRACT to EMPTY redefinition in Component Pascal
by Diego Sardina 11 Apr '18

11 Apr '18

Dear Oberon community, I found an unusual feature while playing a bit with Component Pascal. The report says: "A method redefined by an empty method must be empty or abstract." This sentence means that in later extensions an abstract method can be redefined as an optional/empty. Are there any use-cases for this? MODULE M; TYPE T = ABSTRACT RECORD END; T1 = ABSTRACT RECORD (T) END; PROCEDURE (VAR t: T) P(), NEW, ABSTRACT; PROCEDURE (VAR t: T1) P(), EMPTY; END M. -- Diego Sardina

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