[avr-gcc-list] How to force GCC to not to remove nop statements ?
Hi list,
Like many people I guess, I am using in-lined nop asm statements to
respect the timing of external devices, when toggling their control
lines.
In the case at hand I am driving a text LCD module, and the
Enable line must be pulsed low for 250ns.
void lcd_send_nibble(uint8_t data)
{
...
//pulse Enable line
LCD_PORT |= LCD_E;
__asm__ volatile(nop);
__asm__ volatile(nop);
__asm__ volatile(nop);
__asm__ volatile(nop);
LCD_PORT = ~LCD_E;
}
My AVR was running at 8MHz, so an instruction cycle of 125ns, so two nop
in-lined were spot on, just perfect, and it ran fine.
Today I pushed the AVR (ATmega32) up to its maximum of 16MHz.
So I now need 4 nops not two. So I did that.. and the LCD doesn't work
reliably. Suspecting the problem, I went straight to the generated
assembly, and horror, my 4 nop statements have disappeared !
I made a few trials. It appears that up to and including 3 nop
statements, GCC leaves them alone. But if I put 4 of them, it removes
them all !
Any way to instruct GCC to leave my 4 nops ?
Am using avr-gcc 4.3.2
Regards,
--
Vince
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RE: [avr-gcc-list] How to force GCC to not to remove nop statements ?
-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 Vincent Trouilliez Sent: Thursday, February 19, 2009 11:02 AM To: avr-gcc-list@nongnu.org Subject: [avr-gcc-list] How to force GCC to not to remove nop statements ? Hi list, Like many people I guess, I am using in-lined nop asm statements to respect the timing of external devices, when toggling their control lines. snip Am using avr-gcc 4.3.2 If you are using WinAVR 20081205 then you can use one of the new builtin functions: void __builtin_avr_delay_cycles(unsigned long __n); The prototype can be found in avr/builtins.h, but you shouldn't need the prototype to call it. The parameter is expecting the number of cycles that you want to delay, so in your case this should be: __builtin_avr_delay_cycles(4); And then let gcc handle generating the code for you. ;-) Eric Weddington ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] How to force GCC to not to remove nop statements ?
On Thursday 19 February 2009 19:01, Vincent Trouilliez wrote: I made a few trials. It appears that up to and including 3 nop statements, GCC leaves them alone. But if I put 4 of them, it removes them all ! Are you absolutely sure they are really left out? I assume they are just not shown in the assembly file. Four or more nops are replaced by ellipses, but are present allright. Have a close look at the addresses. Otherwise you could use __asm__ volatile( nop \n\t nop \n\t nop \n\t nop \n\t); in which gcc cannot start to optimize. Ruud ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] How to force GCC to not to remove nop statements ?
Hi Vincent,
If I understand correctly, the word volatile itself is to tell the compiler
not to ignore the statement. I am not sure if your statement is correct, but I
have used
asm volatile (nop::);
and the compiler never removed the nops from code.
Nayani
--- On Thu, 2/19/09, Vincent Trouilliez vincent.trouill...@modulonet.fr wrote:
From: Vincent Trouilliez vincent.trouill...@modulonet.fr
Subject: [avr-gcc-list] How to force GCC to not to remove nop statements ?
To: avr-gcc-list@nongnu.org avr-gcc-list@nongnu.org
Date: Thursday, February 19, 2009, 11:31 PM
Hi list,
Like many people I guess, I am using in-lined nop asm statements to
respect the timing of external devices, when toggling their control
lines.
In the case at hand I am driving a text LCD module, and the
Enable line must be pulsed low for 250ns.
void lcd_send_nibble(uint8_t data)
{
...
//pulse Enable line
LCD_PORT |= LCD_E;
__asm__ volatile(nop);
__asm__ volatile(nop);
__asm__ volatile(nop);
__asm__ volatile(nop);
LCD_PORT = ~LCD_E;
}
My AVR was running at 8MHz, so an instruction cycle of 125ns, so two nop
in-lined were spot on, just perfect, and it ran fine.
Today I pushed the AVR (ATmega32) up to its maximum of 16MHz.
So I now need 4 nops not two. So I did that.. and the LCD doesn't work
reliably. Suspecting the problem, I went straight to the generated
assembly, and horror, my 4 nop statements have disappeared !
I made a few trials. It appears that up to and including 3 nop
statements, GCC leaves them alone. But if I put 4 of them, it removes
them all !
Any way to instruct GCC to leave my 4 nops ?
Am using avr-gcc 4.3.2
Regards,
--
Vince
___
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AVR-GCC-list@nongnu.org
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Re: [avr-gcc-list] How to force GCC to not to remove nop statements ?
On Thu, 19 Feb 2009 11:14:40 -0700 Weddington, Eric ewedding...@cso.atmel.com wrote: If you are using WinAVR 20081205 then you can use one of the new builtin functions: void __builtin_avr_delay_cycles(unsigned long __n); Hmm, sweet ! Unfortunately I am on Linux so no WinAVR for me ! ;-) -- Vince ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
[avr-gcc-list] introducing a new section in data memory
Hello all, I needed to create a buffer of 256 bytes starting at a page boundary (xx00) in the RAM memory (Mega8). I added this line in the makefile LDFLAGs = -wl,--section-start=.test=0x800200 and defined a variable in the .C file (shown below) unsigned char mem3 __attribute__ ((section(.test))); However variable mem3 is being assigned address 0x60 in the controller??? also if I define another global in next line to mem3 I get error that .data and .bss overlap lma 0xa0?? I am of the opinion that all variable defined with attribute .test will be located in that memory area and all other global variables will be located in their native memory. Perhaps if I ma able locate the .test section properly the overlap error may vanish. Can you correct the problem please? Thank you. Nayani ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] How to force GCC to not to remove nop statements ?
On Thu, 19 Feb 2009 10:22:23 -0800 (PST) Parthasaradhi Nayani partha_nay...@yahoo.com wrote: Hi Vincent, If I understand correctly, the word volatile itself is to tell the compiler not to ignore the statement. I am not sure if your statement is correct, but I have used asm volatile (nop::); I used this too, because it's what the avr-libc manual shows, however when I do this, GCC caughs : lcd.c:96: error: ‘asm’ undeclared (first use in this function) lcd.c:96: error: (Each undeclared identifier is reported only once lcd.c:96: error: for each function it appears in.) lcd.c:96: error: expected ‘;’ before ‘volatile’ make: *** [lcd.o] Error 1 the same avr manual (section 9.6.5, macros) suggests that using __asm__ instead of asm (and same for volatile) might help get rid of warnings. So I tried that and it worked.. so I stick with it ;-) -- Vince ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] How to force GCC to not to remove nop statements ?
On Thu, Feb 19, 2009 at 11:14:40AM -0700, Weddington, Eric wrote: If you are using WinAVR 20081205 then you can use one of the new builtin functions: void __builtin_avr_delay_cycles(unsigned long __n); The prototype can be found in avr/builtins.h, but you shouldn't need the prototype to call it. Hey Joerg, you must be busy! FreeBSD's avr-gcc used to track WinAVR closer than this. :-) -- David Kelly N4HHE, dke...@hiwaay.net Whom computers would destroy, they must first drive mad. ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
RE: [avr-gcc-list] How to force GCC to not to remove nop statements?
-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: Thursday, February 19, 2009 12:36 PM To: avr-gcc-list@nongnu.org Subject: Re: [avr-gcc-list] How to force GCC to not to remove nop statements? On Thu, Feb 19, 2009 at 11:14:40AM -0700, Weddington, Eric wrote: If you are using WinAVR 20081205 then you can use one of the new builtin functions: void __builtin_avr_delay_cycles(unsigned long __n); The prototype can be found in avr/builtins.h, but you shouldn't need the prototype to call it. Hey Joerg, you must be busy! FreeBSD's avr-gcc used to track WinAVR closer than this. :-) He has been busy. He's been working on support for the new ATmega128RFA1 device, which has been added recently to the toolchain. Joerg will be including all of the WinAVR patches in his next update of the avr toolchain in FreeBSD Ports. Joerg and I are working closely on the next release. There's been a lot of activity recently on avr-libc and avrdude, with releases of both coming up very soon. ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] How to force GCC to not to remove nop statements?
On Thu, Feb 19, 2009 at 12:46:50PM -0700, Weddington, Eric wrote: Hey Joerg, you must be busy! FreeBSD's avr-gcc used to track WinAVR closer than this. :-) He has been busy. He's been working on support for the new ATmega128RFA1 device, which has been added recently to the toolchain. Joerg will be including all of the WinAVR patches in his next update of the avr toolchain in FreeBSD Ports. Joerg and I are working closely on the next release. There's been a lot of activity recently on avr-libc and avrdude, with releases of both coming up very soon. Thought I ought to reply to make sure its clear that I'm not complaining and very much appreciate the work Eric and Joerg are doing and have done for avr-gcc. Related to another thread: as to why *not* to use an 8051: Doesn't have avr-gcc. -- David Kelly N4HHE, dke...@hiwaay.net Whom computers would destroy, they must first drive mad. ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
RE: [avr-gcc-list] introducing a new section in data memory
-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 Parthasaradhi Nayani Sent: Thursday, February 19, 2009 11:37 AM To: avr-gcc-list Subject: [avr-gcc-list] introducing a new section in data memory Hello all, I needed to create a buffer of 256 bytes starting at a page boundary (xx00) in the RAM memory (Mega8). I added this line in the makefile LDFLAGs = -wl,--section-start=.test=0x800200 First off, is that a typo above? It's suppose to be an uppercase 'W' like so: LDFLAGs = -Wl,--section-start=.test=0x800200 ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] How to force GCC to not to remove nop statements?
David Kelly wrote: Related to another thread: as to why *not* to use an 8051: Doesn't have avr-gcc. So true. Althought it's pointless to add to the recent Freaks AVR vs PIC thread, this is one of the most significant reasons why I prefer the AVR line. They are inexpensive, the programmers can be very inexpensive, and the C toolchain is easily within reach of the hobbyist. I have $40.00 in PICs and a nice programmer sitting usb programmer for them I have never used. I just can't find the value in jumping back to ASM to make use of them. Jim ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
[avr-gcc-list] Preferred ICE (was: How to force GCC to not to remove nop statements?)
David Kelly wrote: I have a Microchip 1000 or 2000 ICE thingy that cost about $2000 and was used for one project. Given a choice I much prefer the ECROS ICE Cube, avr-gcc, and of course an AVR. Could I possibly quote that on the User Testimonials page, please? Now that Atmel have replaced the ATmega16L that the AVR ICE-Cube uses with the ATmega16A, when I get through what I have in stock the next batch will draw *even less* power from the target. For those that are not familiar with the AVR ICE-Cube, let me save you a bit of research and point out that it is a JTAG ICE clone and only works with the small, but very useful, set of devices supported by that debugger interface. It does not support the newer devices for which you need a JTAGICE MkII. But, unlike the AVR Dragon, it does not have a 32 Kbyte limit. Graham. http://www.ecrostech.com ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
[avr-gcc-list] introducing a new section in data memory
Hello all, I sent a mail on the subject but it seems to have got lost and therefore posting again I need to have a buffer of about 256 bytes starting at a page boundary in the ram of Mega8. To get this I introduced a new section and assigned it an address in makefile. I defined variables, to test, using attribute section. However when I try to debug the code I see the variables are allotted memory locations other than specified in the section? My makefile has the following statement LDFLAGs = -wl,--section-start=.test=0x800100 My .C file has the following statements unsigned char mem3 __attribute__ ((section(.test))); int mem5 __attribute__ ((section(.test))); I have also noticed, if I declare a global variable I get overlap error. Please help me solve this problem. Thank you. Nayani ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] Preferred ICE (was: How to force GCC to not to remove nop statements?)
On Feb 19, 2009, at 9:44 PM, Graham Davies wrote: David Kelly wrote: I have a Microchip 1000 or 2000 ICE thingy that cost about $2000 and was used for one project. Given a choice I much prefer the ECROS ICE Cube, avr-gcc, and of course an AVR. Could I possibly quote that on the User Testimonials page, please? Yes you may. But rather than call it a Microchip 1000 or 2000 ICE thingy I checked the closet and its an MPLAB ICE-2000. And appears the current price is $1000 but requires external pods or personality modules. Its significantly more capable than AVR JTAG as its a full emulator that replaces the target MCU. Its just that the software (back then) resembled Windows 3.0 and DOS. And turned out some of its instruction execution times were not the same as a stand alone chip. Microchip has/had a ICD which is similar to Freescale BDM and AVD DebugWire but consumed some program space. But the ICD executed all code with proper timing as it was an enhanced monitor program. As I remember in the end I had to use a mix of the two Microchip development tools to get the job done. -- David Kelly N4HHE, dke...@hiwaay.net Whom computers would destroy, they must first drive mad. ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] How to force GCC to not to remove nop statements?
David Kelly dke...@hiwaay.net wrote: Strangely the JTAGICE mkII didn't work on the above hardware where the ICE Cube did. I put a small 50 mA or maybe 100 mA linear regulator on the 3.3V supply and the mkII drew more power off the target than the regulator would provide. The JTAG ICE mkII cannot be powered from the target circuitry. It needs either a separate power supply, or can be powered directly from USB. -- cheers, Jorg .-.-. --... ...-- -.. . DL8DTL http://www.sax.de/~joerg/NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-) ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] How to force GCC to not to remove nop statements ?
Vincent Trouilliez vincent.trouill...@modulonet.fr wrote: Unfortunately I am on Linux so no WinAVR for me ! ;-) Once I'm done with updating the FreeBSD toolchain (see the other part of this thread), Bingo600's Linux build script will also track that as well. -- cheers, Jorg .-.-. --... ...-- -.. . DL8DTL http://www.sax.de/~joerg/NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-) ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
Re: [avr-gcc-list] How to force GCC to not to remove nop statements ?
Vincent Trouilliez vincent.trouill...@modulonet.fr wrote: lcd.c:96: error: »asm« undeclared (first use in this function) That's because you are using a -std setting the prevents GCC from using its extensions by a name (asm) that is in the application name space, like -std=c99. Either use -std=gnu99, or (as you already did) use the implementation namespace counterpart __asm__. -- cheers, Jorg .-.-. --... ...-- -.. . DL8DTL http://www.sax.de/~joerg/NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-) ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
RE: [avr-gcc-list] introducing a new section in data memory
--- On Fri, 2/20/09, Weddington, Eric ewedding...@cso.atmel.com wrote: First off, is that a typo above? It's suppose to be an uppercase 'W' like so: LDFLAGs = -Wl,--section-start=.test=0x800200 It was a typo. Will test and reply. Thank you for your time. Regards Nayani ___ AVR-GCC-list mailing list AVR-GCC-list@nongnu.org http://lists.nongnu.org/mailman/listinfo/avr-gcc-list
