[TriEmbed] Hacking a fake vintage radio (with Arduino + Pi 0)

Wed Jul 1 10:53:55 CDT 2020

I learned FORTRAN in highschool (late '70s) and converted an Apple ][
Applesoft BASIC interpreter into a FORTRAN-4 interpreter -- I found out
that the two languages were very similar token for token and just edited
the strings recognized for the tokens.  Other than one class project in
college (1980) where we had to use the then already vintage card punch and
batch submit a simulation program (in a C class of all things - they wanted
us to know about FORTRAN because of its connections to SPICE for circuit
analysis), it was 23 years before I would use it again.

I worked a contract at a big food company that was rewriting their
nutrition label database access after a big merger, and since it was on DEC
VAXes running VMS they insisted that it be developed in Fortran so their
MIS folks could maintain it.  (I was primarily a C/C++ programmer in UNIX
and thus a fish out of water, but I was the only poor schlub that would
work the contract)  At that time DEC's Fortran had evolved a lot to go with
free-form whitespace no longer column controlled and no continuation
"cards" - the compiler even allowed macro preprocessors and linking with
the C libraries in order to use RDB database functions and embedded SQL.
Needless to say I utilized all the latest features of DEC Fortran at the
time and my code looked an awful lot like a C program, to the consternation
of the MIS guys.  Their next contract with us ended up in C++ with a lot of
non-object style coding so their MIS guys could maintain it afterwards -
much like the Arduino "Wiring" code of today.

On Wed, Jul 1, 2020 at 11:05 AM John Vaughters via TriEmbed <
triembed at triembed.org> wrote:

> FORTRAN is exactly what I was taught in college, and I was told it is only
> to be used in structured manners that emulate the 'while' statements and
> other structured loops. If you wanted a complete zero on your assignment,
> you would just need to use a goto as label jump and bye bye grade.
>
> BTW - FORTRAN is still the fastest known code next to assembly, especially
> if you use the Intel optimized compiler. We are in the process of replacing
> some FORTRAN code now, but look around, it's still the 800 lb Gorilla for
> heavy computation.
>
> John Vaughters
>
>
>
>
>
>
> On Wednesday, July 1, 2020, 10:45:41 AM EDT, Rick DeNatale via TriEmbed <
> triembed at triembed.org> wrote:
>
>
>
>
>
>
> How many of you are old enough to remember FORTRANs computed go to, and
> its evil twin the computed come from.
> https://web.archive.org/web/20180716171336/http://www.fortran.com/fortran/come_from.html
>
>
>
> > On Jul 1, 2020 at 9:13 AM, <Scott Hall via TriEmbed> wrote:
> >
> > NO NO, DON'T USE GOTO !
> >
> > Seriously though, this has been a behaviour of the Arduino compiler
> compilation for a while -- its even mentioned in some Arduino books.  The
> workaround is to have a single function called for each case label and to
> put the statements desired with the function.  This gets optimized to a
> jump table anyway, so its just a matter of doing this in practice.
> >
> > On Wed, Jul 1, 2020 at 12:34 AM Jon Wolfe via TriEmbed <
> triembed at triembed.org> wrote:
> >> Yep, GCC has a ton of extensions to C and C++, though they obviously
> need careful consideration when using, if it’s work the downside of making
> the code less portable.
> >>
> >> https://gcc.gnu.org/onlinedocs/gcc-5.2.0/gcc/C-Extensions.html
> >>
> >> One of my favorites is local functions.
> >>
> >>
> >>
> >> From: Rodney Radford
> >> Sent: Tuesday, June 30, 2020 9:04 PM
> >> To: Jon Wolfe
> >> Cc: Brian; Triangle Embedded Computing Discussion
> >> Subject: Re: [TriEmbed] Hacking a fake vintage radio (with Arduino + Pi
> 0)
> >>
> >> I had never heard of the GCC label variable, so I had to google it...
> wow, I learned something new tonight!
> >>
> >>
> https://stackoverflow.com/questions/1777990/is-it-possible-to-store-the-address-of-a-label-in-a-variable-and-use-goto-to-jum
> >>
> >>
> >> On Tue, Jun 30, 2020 at 8:57 PM Jon Wolfe via TriEmbed <
> triembed at triembed.org> wrote:
> >>>
> >>> There is a trick you can use with gcc that is a non-standard C
> construct where you can use ‘goto’ and give it a variable containing the
> address of a label. You then create an array of label address and you can
> then dynamically index that array to jump to various locations.  I’ve seen
> it used as an optimization technique, and you can also have more control
> over the program flow, though it is using the infamous keyword, Essentially
> though it end up looking pretty much like a switch-case.
> >>>
> >>> That is really odd about that gcc bug.  It’s not like I’ve never seen
> them, but 99.9% of the time when I thought I had found a compiler bug in
> C/C++, it turns out to be something else. (hafl the time one of those
> things that disappears with a “clean/rebuild all”)  I remember the Arduino
> /AVR/gcc linker used to have a bug related to 8-bit AVR chips that had more
> than 64KB of flash memory, such as the ATMega 1284. Those chips address by
> 16 bit words not bytes, so 128kb of flash is accessible without trick likes
> far pointers, but the linker would mess up the address calculations
> sometimes I think for interrupt handlers or functions called by interrupt
> handlers that crossed the 64kb boundary.
> >>>
> >>>
> >>> From: Huan Truong via TriEmbed
> >>> Sent: Tuesday, June 30, 2020 12:48 PM
> >>> To: Brian
> >>> Cc: Triangle Embedded Computing Discussion
> >>> Subject: Re: [TriEmbed] Hacking a fake vintage radio (with Arduino +
> Pi 0)
> >>>
> >>> Oh yeah, that explains my issue. I definitely ran into that issue
> >>> where I have checked and had no reason to believe I was doing
> >>> something wrong, yet, when I evacuated each switch to a function, the
> >>> switch worked correctly. But neither scoping with an anonymous scope
> >>> nor renaming the variables work.
> >>>
> >>> The reason I used the switch was that I read on stackoverflow at one
> >>> point and someone said that we should use switches instead of elseifs
> >>> when we have a lot of cases. Then, using switches, the compiler will
> >>> be able to (at some point) create a lookup table for you so it's
> >>> faster. I doubt that was what happening at least on the Arduino case.
> >>> You'll need a giant lookup table which the uCs don't have memory for.
> >>> I suspect that in a lot of cases, using switches is probably just as
> >>> slow as using elseifs. Now as I see that it is so buggy, I probably
> >>> will not use switches, at least on Arduino.
> >>>
> >>> Cheers,
> >>> - Huan.
> >>>
> >>> On Tue, Jun 30, 2020 at 9:23 AM Brian via TriEmbed
> >>> <triembed at triembed.org> wrote:
> >>>>
> >>>> Side note:
> >>>>
> >>>> The arduino compiler has bugs in how it handles switch statements.
> I've
> >>>> run into situations lately where the order of the case statements
> matter
> >>>> (which it never should); cases are completely ignored, etc.
> >>>>
> >>>> I believe it may be tied to the use of local scoping within a case,
> e.g.:
> >>>>
> >>>> switch(thing) {
> >>>> case 1:
> >>>> {
> >>>> // stuff with case-local scope
> >>>> }
> >>>> break;
> >>>> }
> >>>>
> >>>> Syntactically- and semantically-correct code has proven to generate
> >>>> incorrect runtime results.
> >>>>
> >>>> I haven't had time/motivation to submit a bug report, but I should do
> >>>> that. At any rate, a potential workaround is to reorder your cases.
> >>>>
> >>>> -B
> >>>>
> >>>> On 6/24/20 9:51 PM, Huan Truong via TriEmbed wrote:
> >>>> > Thanks Pete!
> >>>> >
> >>>> > I feel like there was something really mysterious about the switch
> statement. Even if I pasted the whole blocks of code of each function I
> would have called to the {} inside a case, the code still wouldn’t work.
> That baffled me by a mile.
> >>>> >
> >>>> > But yeah, I spent way too much time on the project that I’m
> comfortable with the idea of not understanding some of it now. The watchdog
> timer code was baffling too.
> >>>> >
> >>>> > Please excuse my typos, sent from phone.
> >>>> >
> >>>> > On Jun 24, 2020, at 10:14 AM, Pete Soper via TriEmbed <
> triembed at triembed.org> wrote:
> >>>> >
> >>>> > What a beautifully presented adventure. Loved reading it. And when
> you say a problem "could be bad" you make your point. :-) (meant as a "find
> Waldo" exercise for alert readers)
> >>>> >
> >>>> > Hadn't heard of "kev" or any other Arduino emulator for that
> matter. That aspect was interesting too.
> >>>> >
> >>>> > The other issue with redeclaration of the vars local to the switch
> statement is that they literally don't exist outside it, so communicating
> their values outside the block would be difficult. :-) In general, every {}
> defines a local scope in C/C++ and you can declare variables inside that
> scope but they cease to be defined outside the scope. The scope outside any
> {} (aka "global") or vars declared "static" can avoid this issue but not
> the redefine issue.
> >>>> >
> >>>> > Thanks for sharing this!
> >>>> >
> >>>> > Pete
> >>>> >
> >>>> >
> >>>> >> On 6/24/20 12:43 PM, Huan Truong via TriEmbed wrote:
> >>>> >> This has taken me way more time than I thought, but finishing this
> >>>> >> retrofit is a big achievement for me. It's really silly and serves
> >>>> >> exactly no purpose other than RE'ing something no one cares about.
> So
> >>>> >> I just want to share for some shits and giggles.
> >>>> >>
> >>>> >>
> http://www.tnhh.net/posts/adventures-hacking-fake-vivitar-vintage-radio.html
> >>>> >>
> >>>> >>
> >>>> >>
> >>>> >>
> >>>> >>
> >>>> >
> >>>> > _______________________________________________
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> >>>
> >>>
> >>> --
> >>>
> >>> Huan Truong
> >>> www tnhh.net / twitter @huant
> >>>
> >>> _______________________________________________
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> >>
> >
> >
> > --
> > Scott G. Hall
> > Raleigh, NC, USA
> > scottghall1 at gmail.com
> > Although kindness is rarely a job, no matter what you do it's always an
> option.
> > _______________________________________________ Triangle, NC Embedded
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-- 
Scott G. Hall
Raleigh, NC, USA
scottghall1 at gmail.com
*Although kindness is rarely a job, no matter what you do it's always an
option.*
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