Alharad 
Hi,
I really want to get started with AVR assembly but I need a mentor. I have some tutorials online but there are a few commands I don't quite understand. if someone would please help me out i would very much appreciate it, so PM me for my skype or MSN account.
i am a high-school student and got the AVRISP mkII with AVRStudio4 and WinAVR downloaded.
Thanks in advance!!!! :)
js 
I need a mentor
Alharad I don't know, which do you think would be better for an assembler?
js The Atmel assembler is "simpler". There is no magic mentoring, all you need to do is LOTS of practise just like when you want to learn any other language.
Are you proficient in assembler for any processor family? Is it just the "AVR" part that you need help with, or is it the whole "assembly language" thing?
Alharad It is the assembly language thing, since I don't know it but want to learn. I think I can understand the AVR part pretty well if i look at the datasheet of the AVR i am using.
i requested some samples from Atmel, hopefully I'll get them :)
MBedder Alharad Wow thanks, this is very helpful!
Alharad Is this with Studio asm or WinAVR asm?
MBedder Studio. Yet the common recommendations/guidelines are essentially the same.
Alharad This is definitely for fun, and i would really, really like to learn asm.
Thanks for all the help so far
geoelec Even if use C all the time to write code for avr it is useful to have an idea what is behind C commands and how these commands are translated into avr code.So it useful to learn assembly getting this way more familiar yourself to the architectural of the specific mcu's.
And its very useful in time critical applications also.
And as any other knowledge you get in life is something that remains and never get lost.
MBedder
assembly is one of the hardest language to learn and one of the hardest language to use. It is incredibly to build up a usable assembly code base, and it is even harder to transport your assembly skills from one family of mcus to another.
assembly is one of the hardest language to learn and one of the hardest language to use.
geez ... Alharad, if he's a newbee, will believe this if we let it go. Lying to him helps no-one at all.
geoelec Maybe assembly is the easiest thing to learn on this planet,maybe not.But modifications,and transportations to another device of the ready code are very difficult.
First choose the appropriate device that meets application specifications and then start writing any code.
If you are studying medicine it is not neccessary to learn assembly.In learning of any mcu i think its neccessary.
indianajones11 Make sure you get the AVR assembler and instruction set manuals. To get the most out of this forum, you'll need to learn C eventually because most of what's here is written in C.
I recommend the tutorial forum, esp. timers / PWM, and how to use avr studio tuts. What are the instructions you don't understand ? What MCU do you have ?
https://www.avrfreaks.net/index.p...
http://www.avrbeginners.net/
jgmdesign 
I was gonna leave this alone BUUUUUUUUUUUUTTTT!!!!
I can read and somewhat understand 'C', but to write a program I am a dead duck. I have used assembler for close to 20 years, and I agree with some of the posts that If you are getting started 'C' is probably the best course to possibly follow(F#$%^, I cannot believe I said that, sorry js)
None the less it is very difficult to remember the commands for various processors where 'C' can be debugged after compiliation from one platform to another without much asprin to kill the headache.
This community has many phenominal gurus on both assember and "c" Use them.
WElcome, and Good luck to you.
Jim
js F#$%^, I cannot believe I said that,
start from avr tutorial..expecially moron tutorial.
Regards
Jeckson
avrbeginners.net is another good assembly language resource.
http://www.avr-asm-tutorial.net/avr_en/index.html
The site is still maintained, every now and then there is something "new on this page". It tells you everything about how to get things like a keypad or HD44780 character display working.
Mister Gerhard Schmidt is a True Assembly Programmer who will never convert to C.
And get a modern USB connected STK200 boeard from Kanda.com. Many people here may want to give away an old STK200.
Many example asm programs are here: http://avr-asm.tripod.com/
Alharad I've been looking through the AVR tutorials, and it doesn't seem so bad. The best way for me to become good at anything is just practice, which I've noticed while learning C. I appreciate all the help so far, you've made it easier for me to learn assembly. I will let you know if i have any other questions or get stuck, and i hope you will all be just as helpful! :)
stevech Best way to learn C, I feel, is to write some dumb console programs in C (not C++) using free C compiler for MS WIndows, such as Visual Studio Express or there are several other freebies.
Then you can debug, catch bad pointers, etc. On a micro, it just inexplicably fails to blink the LED. Unless you sprinkle lots of printf() or have a JTAG debugger.
Alharad Yea, it's really good to get practice in! Theory can only take you so far, and then you have to get down and do it. Plus you remember more from experience!!
Alharad I have one question now. The Data Direction Register sets your I/O ports as inputs or outputs. The PORT register sets whatever port you have as a high or low. But I'm wondering if I have this right
START: LDI LED, LOW(RAMEND) ; Setup Stack Pointer OUT SPL, LED ; So calls to subroutines LDI LED, HIGH(RAMEND) ; Work correctly OUT SPH, LED LDI LED, 0xFF ; Set all PORTB for output OUT DDRB, LED ; Write 1's to Direct in Regs
so to set outputs with DDRB i have to set it has 1's, right? so if i wanted the first bit to be an input for a switch maybe it would be:
LDI LED, 0xFE OUT DDRB, LED
is that right?
js is that right?
Also you can use bit NAMES for the bits you want set as one. ie
#define SCK PB5 ;SCK pin #define Miso pb4 ;Miso pin not used #define Mosi pb3 ;Master data out #define latch_enable pb2 ;Latch enable bit (SPI /SS pin) #define PWM PB1 ;PWM brightness pin #define input PB0 ;External input . . . ldi temp,(1<<Miso | 1<<input | 1<<latch_enable | 1<<PWM) ;Enable pull ups out portb,temp ;set /SS (latch_enable) and PWM high ldi temp,(1<<SCK | 1<<Mosi | 1<<latch_enable | 1<<PWM) ;PORTB B0=input and B4=Miso as inputs out DDRB,temp
Alharad Here is my first blinking LED program, does it look ok?
.INCLUDE "M8DEF.INC" ; Define Registers .DEF TEMP = R16 ; LED I/O Port .DEF I = R21 ; Index for Loop Control .DEF J = R22 .ORG 0 START: LDI TEMP, LOW(RAMEND) ; Setup Stack Pointer OUT SPL, TEMP ; So calls to subroutines LDI TEMP, HIGH(RAMEND) ; Work correctly OUT SPH, TEMP LDI TEMP, 0xFF ; Set all PORTB for output OUT DDRB, TEMP ; Write 1's to Direct in Regs ; Main Routine BLINK: SER TEMP ; Turn LED ON OUT PORTB, TEMP RCALL PAUSE ; Delay Subroutine CLR TEMP ; Turn LED OFF OUT PORTB, TEMP RCALL PAUSE ; Delay Subroutine RJMP BLINK ; Loop back to main routine ; Subroutines PAUSE: CLR J PLUPE: NOP DEC J BRNE PLUPE RET
I'm not very sure why i need to use a I/O register in order to loop? can't I use a variable like in C?
Koshchi I'm not very sure why i need to use a I/O register in order to loop?
Alharad Could you explain a GP variable? What does it stand for and what does it do?
Lennart Newer models can toggle pin state using PINx istead of PORTx.
So this code (which changes all pins of PORTB)
BLINK:
SER TEMP ; Turn LED ON
OUT PORTB, TEMP
RCALL PAUSE ; Delay Subroutine
CLR TEMP ; Turn LED OFF
OUT PORTB, TEMP
RCALL PAUSE ; Delay Subroutine
RJMP BLINK ; Loop back to main routine
could be replaced by
BLINK:
sbi pinB, LED ;toggle LED
RCALL PAUSE ; Delay Subroutine
RJMP BLINK ; Loop back to main routine
This toggles only the pin where LED is connected. You need to define that pin such as
.def LED = 2 or whatever pin you're using.
MBedder You need to define that pin such as
.def LED = 2 or whatever pin you're using.
Lennart Bullshit. The .def directive deals with registers, not with bits/pins.
.equ LED = 2
JohanEkdahl 
Could you explain a GP variable?
js .def directive deals with registers
. . . #define days_counter r6 ;Calculated number of days to target date #define scroll_n_bits r5 ;Number of bits to rotate dis buffer for scroll #define hundreds r4 ;Hundreds for HTOD8 and DTOH8 #define tens r3 ;Tens for HTOD8 and DTOH8 #define units r2 ;Units for HTOD8 and DTOH8 //#define r1 ;Leave unused for MUL //#define r0 ;Leave unused for MUL #define monitor_timeout 4000 ;In 1ms counts (4000 4s) #define input_buffer_size 16 ;16 bytes monitor input buffer size #define PKIO_DATA_SIZE 100 ;256 max. ($FF) #define display_size 5 ;Size of display 5, 10, 15, 20 or 25 . . #define PWM PB1 ;PWM brightness pin #define input PB0 ;External input
MBedder MBedder Then please come back when your 2nd week of programming class is complete :D:D:D
js Unless the assembler compiler is just written by some bonehead,
LIST P=16f877
#INCLUDE "P16f877.INC"
.
.
; Built with IAR Embedded Workbench Version: 3.21A
;*****************************************************************************
#include
.
.
$INCLUDE "\EVM11\DAT2\68HC11EX.ASM"
It is possible however, because assembler is such an advanced language, that the professsor doesn't cover these things untill much later in the programming course.
jgmdesign @js
I hope you didn't write this in front of junior!! Go wash your mouth with soap now....
Nahh, he was sleeping.
I guess you have truly went to the dark side or became a weenie since you became a moderator. :D
I can remember you defending assembler over 'C' vehemently. Oh well. I guess I am the last hope for the Jedi(lol)
Jim
Edit:
Cannot spell 'Truly" either
js I guess you have truly went to the dark side
Never fear, there are many of us that still prefer assembly.
jgmdesign Never fear, there are many of us that still prefer assembly.
Bless you
Jim
Never fear, there are many of us that still prefer assembly.
After a few initial mindset and pointer/address hurdles I really can't see myself ever going back. I've converted a large handcrafted ASM app to CVAVR, expanded it to include floating point maths and floating point printf and it's about around 5% bigger (code size) than the the original.
I don't regret the assembly journey one bit - down and dirty with the chip and ASM is a great way to understand exactly how things work. It also allows you to look at, and understand, the compiler .lst file output to see how your C code is being to turned into ASM if you're unsure about anything.
I did dally with GCC in the past, but it just seemed to alienate me with its complexity when doing some things. I've found CVAVR very simple to grasp...
gbestwick .DEF TEMP = R16 ; LED I/O Port .DEF I = R21 ; Index for Loop Control .DEF J = R22
Just a small suggestion, is that you use more descriptive names on your Registers. Just like variables in other languages, a more descriptive name really really helps with assembly.
One thing to remember when programming asm is that you will tend to reuse a few registers for "general" use. Like a "temp" register that is never used for anything but throwaway values. Also, don't forget that when using the stack, it isn't the monster size that is available on other platforms. Recursion can be death on an AVR.
As was stated before R0-R31 are called the General Purpose Registers. The reason for this as they can be used for a multitude of things.
The Registers from 16-25 are the ones that most of the Opcodes work with. Some, (MUL) put their results in R0:R1. R26-R31 are your X,Y,Z registers, and if you use them for other things bad bad stuff can happen.
As with any other languages there are always many different ways to accomplish the same thing, however with a low level language such as this you are able to be very efficient and also screw up massively from a single boo-boo.
(I have to stop tying, the editor here is driving me nuts)
I have to stop tying, the editor here is driving me nuts