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twofingers

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Joined: 02/06/2014
Location: Germany
Posts: 1769

Posted: 12:51pm 22 Jun 2024

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As an alternative to Peter's code, we can also use the following:

'x$="bb10d5a6"
'x$="4640e400"
x$="c640e733"
Print x$
Print CDBL2(x$)
End

Function CDBL2(x$)
Local i%,z$
For i% = 7 To 1 Step -2
z$=z$+Chr$(Val("&h"+Mid$(x$,i%,2)))
Next
CDBL2=Str2bin(SINGLE, z$)
End Function

Only tested with the three values!

Regards
Michael

edit:
But Johns function is 20% faster!

disco4now said ... I also have a need to go the other way, sending the value in a double precision float to a CAN bus controlled power supply which expects 4 bytes coded as a single precision float.
Gerry

I think this can be done with

d$= Bin2str$(single, a!, BIG)

.

Just for me, this is the thread that triggered the problem.
Edited 2024-06-23 00:23 by twofingers

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JohnS
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Joined: 18/11/2011
Location: United Kingdom
Posts: 4378

Posted: 03:02pm 22 Jun 2024

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It's not my function, really - it's Peter's. All I did was tweak his code.

John

twofingers

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Joined: 02/06/2014
Location: Germany
Posts: 1769

Posted: 03:14pm 22 Jun 2024

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@John
All good! It's Peter's code and you wrapped it in a function. I don't think Peter is jealous.

Kind regards (and it's always a pleasure to see/read something from you)
Michael

‚My name is Ozymandias, king of kings
Look on my works, ye Mighty, and despair!‘
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare
The lone and ...

phil99

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Joined: 11/02/2018
Location: Australia
Posts: 3376

Posted: 05:28am 23 Jun 2024

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twofingers said I think this can be done with
d$= Bin2str$(single, a!, BIG)

And if you need to convert that to Hex:-

out$="":for n=1 to 4:out$=out$+hex$(STR2BIN(uint8,mid$(d$,n,1)),2):next:?out$

out$=""
a! = -0.002210000064
for n=1 to 4
out$=out$+hex$(STR2BIN(uint8,mid$(Bin2str$(single, a!, BIG),n,1)),2)
next
Print out$

> RUN
BB10D5A6
>

Or as a Function:-

Function CSGL$(a!)
'you pass in the 8 byte double-precision float number
Local out$="", sgl$=""
sgl$= Bin2str$(single, a!, BIG)
For n=1 To 4
out$=out$+Hex$(Str2bin(uint8,Mid$(sgl$,n,1)),2)
Next
CSGL$ = out$
End Function

> ? csgl$(cdbl("abcd012"))
0ABCD012
>
> ? cdbl(csgl$(-1.463246299e-12))
-1.463246299e-12
>

Edited 2024-06-23 17:01 by phil99

CaptainBoing

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Joined: 07/09/2016
Location: United Kingdom
Posts: 2171

Posted: 10:00am 23 Jun 2024

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Excellent work.

I put those two functions on an MMX (double precision)

> ?pi
3.141592654
> ? CSNG$(pi)
40490FDB
> ? CDBL("40490FDB")
3.141592741 <--- clearly some "rounding error" due to loss of granularity but likely close enough
> ? pi - 3.141592741
-8.741020707e-08
>

scribbled following to POKE "40490FDB" into a float on a MM Mk2 (single precision IEEE754 - same as that ACS7262)

> list
Dim a$="40490FDB"
Dim q As float

For n=0 To 3
Poke VAR q, 3-n, Val("&h"+Mid$(a$,(2*n)+1,2))
Next

Print q

> RUN
3.14159
>

Well done all.

h
Edited 2024-06-24 05:46 by CaptainBoing

zeitfest
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Joined: 31/07/2019
Location: Australia
Posts: 701

Posted: 08:30am 24 Jun 2024

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Looks good - especially as I get the same values

[ f77 automatically converts double precision to single when required ]

Running

PROGRAM singval
DOUBLE b
REAL c
b = 3.141592654
c = b
FORMAT (A,F15.9,/)
WRITE (6,0) "b = ", b
WRITE (6,0) "c = ", c
END
\

b = 3.141592654
c = 3.141592741

OK

Edited 2024-06-24 18:32 by zeitfest

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