Hi,
I tried to store some data in flash memory using pgmspace.h.
It works well in C programs but I found that using C++ the things go wrong.
My sample code is:
$ cat x.c
#include avr/io.h
#include avr/pgmspace.h
prog_uint8_t table[] = {
0x01,
0x02,
0x03
};
uint8_t x;
void
-Original Message-
From:
avr-gcc-list-bounces+eweddington=cso.atmel@nongnu.org
[mailto:avr-gcc-list-bounces+eweddington=cso.atmel@nongnu.
org] On Behalf Of Kövesdi György
Sent: Wednesday, March 04, 2009 2:35 AM
To: avr-gcc-list@nongnu.org
Subject: [avr-gcc-list]
Does anyone have any working sample code that shows how to convert 10 bit
ADC outputs into floating points using GCC.
I need to work with floating points on an ATtiny25.
Best Regards,
Rodney
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On Wed, 04 Mar 2009 18:18:22 -0800
Rodney McCray res1z...@verizon.net wrote:
Does anyone have any working sample code that shows how to convert 10
bit ADC outputs into floating points using GCC.
I need to work with floating points on an ATtiny25.
Best Regards,
Rodney
Many of the newer AVRs, Tiny88 for example, let you dynamically change
the CPU clock
frequency. However the AVR-LibC based delays always assume
a fixed frequency based on F_CPU.
I'll always know what frequency I'm at when I call a delay() function.
Is there a way of doing:
_delay_us( double
I'll always know what frequency I'm at when I call a delay() function.
Is there a way of doing:
_delay_us( double __us, uint32_t f_cpu )
and still have the compiler generate code that does not
invoke floating point at run time?
I could make a delay function for each clock
How would I construct a lookup table of logarithms in program memory?
I'll need the logarithm of N entries between 0 and 1, ex: If N = 10, then I
need log(0), log(0.1), log(0.2) etc.
I don't know what precision I'll need yet, but I'll need to be adjusting N,
so manually creating the table with a
-Original Message-
From:
avr-gcc-list-bounces+eweddington=cso.atmel@nongnu.org
[mailto:avr-gcc-list-bounces+eweddington=cso.atmel@nongnu.
org] On Behalf Of Bob Paddock
Sent: Wednesday, March 04, 2009 9:00 AM
To: AVR-GCC
Subject: [avr-gcc-list] Using delay functions
On Wed, Mar 4, 2009 at 12:05 PM, David VanHorn d...@mobilefusioninc.com wrote:
How would I construct a lookup table of logarithms in program memory?
I'll need the logarithm of N entries between 0 and 1, ex: If N = 10, then I
need log(0), log(0.1), log(0.2) etc.
I don't know what precision
David VanHorn wrote:
How would I construct a lookup table of logarithms in program memory?
I'll need the logarithm of N entries between 0 and 1, ex: If N = 10,
then I need log(0), log(0.1), log(0.2) etc.
I don't know what precision I'll need yet, but I'll need to be
adjusting N, so manually
The delay functions require a constant so the delay can be calculated at
compile time. I would think that part of the problem is that you have to
introduce more code to check the value of f_cpu and to calculate the delay.
This pushes the delay calculation into run-time, plus it adds more
-Original Message-
From:
avr-gcc-list-bounces+eweddington=cso.atmel@nongnu.org
[mailto:avr-gcc-list-bounces+eweddington=cso.atmel@nongnu.
org] On Behalf Of David VanHorn
Sent: Wednesday, March 04, 2009 11:46 AM
To: AVR-GCC
Subject: Re: [avr-gcc-list] Using delay
David VanHorn wrote:
How would I construct a lookup table of logarithms in program memory?
I'll need the logarithm of N entries between 0 and 1, ex: If N = 10,
then I need log(0), log(0.1), log(0.2) etc.
I don't know what precision I'll need yet, but I'll need to be adjusting
N, so manually
Before you get that far, what do you want the logs for? And what base (if
it matters)? And what speed and accuracy? If you need low speed and high
accuracy, just use the standard C log function. If you need high speed and
low accuracy and low code space, a find-first-one function will
probably something like this
#define REF_VOLTAGE 2.56
float voltage = 0.0;
voltage = ADC_VALUE * ( refVoltage / 2 ^ 10 );
double check that the compiler compiled the part in parentheses to a
constant.
As others have said, you will want to do fixed point math or other
unit scaling
Message: 2
Date: Wed, 4 Mar 2009 13:05:39 -0500
From: David VanHorn d...@mobilefusioninc.com
Subject: [avr-gcc-list] Tables
To: AVR-GCC avr-gcc-list@nongnu.org
Message-ID:
a8ed8b370903041005q5638beb8m66021895f9a11...@mail.gmail.com
Content-Type: text/plain; charset=iso-8859-1
How
The C preprocessor is too basic to do this sort of thing. Functions like
logarithms come from the math library the the preprocessor can't make
use of libraries at compile time.
This is a PERL script I use to generate sine tables to load onto a
Mega48. It shouldn't be hard to adapt it to
David VanHorn schrieb:
Speed is primary, I need to get the conversion absolutely as fast as
possible.
Accuracy is secondary.
Once I have the logs, the rest of the calculation would be fixed point.
My output will be a 16 bit binary value, the sum of N log values.
My question comes down to
Bob Paddock graceindustr...@gmail.com wrote:
Is there a way of doing:
_delay_us( double __us, uint32_t f_cpu )
and still have the compiler generate code that does not
invoke floating point at run time?
#undef F_CPU
#define F_CPU new_value
_delay_us(us);
F_CPU is always evaluated
F_CPU is always evaluated upon each invocation, so if you ever change
it within one compilation unit, the next invocation of one of these
macros will reflect this.
That's compile-time, he's looking for execution-time changes in processor
speed.
He didn't explicitly say so, but I think he's
David VanHorn wrote:
F_CPU is always evaluated upon each invocation, so if you ever change
it within one compilation unit, the next invocation of one of these
macros will reflect this.
That's compile-time, he's looking for execution-time changes in processor
speed.
He didn't explicitly say so,
On Wed, Mar 04, 2009 at 04:37:22PM -0500, David VanHorn wrote:
F_CPU is always evaluated upon each invocation, so if you ever
change it within one compilation unit, the next invocation of one of
these macros will reflect this.
That's compile-time, he's looking for execution-time changes
-Original Message-
From:
avr-gcc-list-bounces+eweddington=cso.atmel@nongnu.org
[mailto:avr-gcc-list-bounces+eweddington=cso.atmel@nongnu.
org] On Behalf Of David Kelly
Sent: Wednesday, March 04, 2009 2:59 PM
To: David VanHorn
Cc: AVR-GCC
Subject: Re: [avr-gcc-list]
David VanHorn wrote:
Ok, I'll have to see what it takes to do this in windows.
If this is How do I run PERL scripts in Windows, get ActivePerl from
ActiveState:
http://www.activestate.com/activeperl/
Graham.
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On Thursday 05 March 2009 01:06:58 j...@lillahusetiskogen.se wrote:
The big question is, why would you like to do something like that in a
processor like ATtiny25? Why not 32 bit fixed point?
Somewhat related..
Does anyone have or know of a compact fixed point library?
(Not that I have looked
Thanks Eric,
I will get back to you if I run into any trouble.
Best Regards,
Rodney
-Original Message-
From: Weddington, Eric [mailto:ewedding...@cso.atmel.com]
Sent: Wednesday, March 04, 2009 7:50 AM
To: Rodney McCray; AVR-GCC-list@nongnu.org
Subject: RE: [avr-gcc-list] Floating Point
-Original Message-
From:
avr-gcc-list-bounces+eweddington=cso.atmel@nongnu.org
[mailto:avr-gcc-list-bounces+eweddington=cso.atmel@nongnu.
org] On Behalf Of Daniel O'Connor
Sent: Wednesday, March 04, 2009 4:36 PM
To: avr-gcc-list@nongnu.org
Subject: Re: [avr-gcc-list]
On Thursday 05 March 2009 10:11:46 Weddington, Eric wrote:
Somewhat related..
Does anyone have or know of a compact fixed point library?
(Not that I have looked I'll be honest)
Yes. There have been posts about fixed point support in AVR GCC and
avr-libc, I believe on this list and a post
David Brown david.br...@hesbynett.no wrote:
However, the compiler has a much
better chance of doing bounds checking, alias checking, and other
optimisations on the array expression.
Why? Either the compiler knows at compile-time that foo is actually
an array it has detailed information
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