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Author Topic: Why not (finally) expose main.cpp to the user ?  (Read 3602 times)
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But why hide something that is SIMPLE ?

To you it is simple... for someone that just started in programming and embedded devices (which is probably the majority of Arduino users) main() makes a lot less sense than setup() and loop().

I can understand you. I only use the board and the bootloader from Arduino, but I also see why Arduino is made the way it is now. But the good thing is that it allows people to evolve and try different ways of using the hardware and software according to their own personal knowledge.
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This came up in another thread as well - do you know how to download a sketch via the ICSP pins using the IDE?

Adding entries to boards.txt similar to below works for me (I have others that are just different clock freqs). Your programmer may vary ;-)

Code:
uno16.name=Arduino Uno ICSP @ 16MHz
uno16.upload.using=arduino:usbtinyisp
uno16.upload.protocol=stk500
uno16.upload.maximum_size=32256
uno16.upload.speed=115200
uno16.bootloader.low_fuses=0xff
uno16.bootloader.high_fuses=0xde
uno16.bootloader.extended_fuses=0x05
uno16.bootloader.path=optiboot
uno16.bootloader.file=optiboot_atmega328.hex
uno16.bootloader.unlock_bits=0x3F
uno16.bootloader.lock_bits=0x0F
uno16.build.mcu=atmega328p
uno16.build.f_cpu=16000000L
uno16.build.core=arduino
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So you replace

uno16.bootloader.file=optiboot_atmega328.hex

this file with the sketch file to use instead?
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@Nick:

That doesn't seem to work on 1.0 for me. I have to add the 'weak' attribute there.
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I don't have version 1.0.  I thought I had version 0022, but I suppose that is alpha, right?

I can't find version version 1.0 on the download page.

I wonder why version 0022 works? They don't have the weak attribute.
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@CrossRoads: no.

Code:
##############################################################
#
# to activate this board, select it and use:
#
# 'Burn Bootloader' - 'w/ USBtinyISP' just once
# this makes sure the correct FUSE settings are used
#
8x8RGBLedMatrix1.name=8x8 RGB LED Matrix - ATmega168 / 16MHz Quartz / USBtiny
8x8RGBLedMatrix1.upload.maximum_size=16384
8x8RGBLedMatrix1.upload.speed=115200
8x8RGBLedMatrix1.upload.using=arduino:usbtinyisp
8x8RGBLedMatrix1.bootloader.low_fuses=0xFF
8x8RGBLedMatrix1.bootloader.high_fuses=0xDD
8x8RGBLedMatrix1.bootloader.extended_fuses=0x05

## just so the IDE doesn't throw an error
## it will be overwritten, but we need the correct FUSE settings
8x8RGBLedMatrix1.bootloader.path=optiboot
8x8RGBLedMatrix1.bootloader.file=optiboot_diecimila.hex
##

8x8RGBLedMatrix1.bootloader.unlock_bits=0x3F
8x8RGBLedMatrix1.bootloader.lock_bits=0x3F
8x8RGBLedMatrix1.build.mcu=atmega168
8x8RGBLedMatrix1.build.f_cpu=16000000L
8x8RGBLedMatrix1.build.core=arduino
#
#
#
##############################################################

If I want to do without a bootloader, I change the fuse settings, lockbits and the available flash size to respect that fact. Uploading works as usual.

Uploading is currently slower with an usbtiny than with optiboot. There is a trivial 'patch' for that, but it was not accepted... it involves adding the bitclock parameter '-B 1' to the programmers.txt and a tiny modification in the java code that deals with uploading. This would increase upload speed at least 10x.

programmers.txt
Code:
usbtinyisp.name=USBtinyISP
usbtinyisp.protocol=usbtiny
usbtinyisp.bitclock=1

app/src/processing/app/debug/AvrdudeUploader.java
Code:
@@ -104,6 +104,10 @@ public class AvrdudeUploader extends Uploader  {
Map<String, String> programmerPreferences = target.getProgrammers().get(programmer);
List params = new ArrayList();
params.add("-c" + programmerPreferences.get("protocol"));
+
+ if (programmerPreferences.get("bitclock") != null) {
+ params.add("-B" + Integer.parseInt(programmerPreferences.get("bitclock")));
+ }

if ("usb".equals(programmerPreferences.get("communication"))) {
params.add("-Pusb");

I have given up getting anything added/patched in the IDE, it has proven to be pointless for me. I just complain here.

This will be ignored too I guess, but it is less painful for me overall.
« Last Edit: October 12, 2011, 02:59:35 pm by madworm » Logged

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Let's just use main:
O.O I had no idea you could do that and this is 100% awesome. I just shaved 132 bytes off my sketch and now have enough space to implement a URL decode function (94 bytes) to fix that bug that's been annoying me for months.

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See! It is useful.
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O.O I had no idea you could do that and this is 100% awesome. I just shaved 132 bytes off my sketch and now have enough space to implement a URL decode function (94 bytes) to fix that bug that's been annoying me for months.

Glad that helped. Better not upgrade to version 1.0 though, unless they fix that <hint>.
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You CAN use main() instead of setup() and loop().  Really, yes, you can.

Quote
void setup() {
  Serial.begin(9600);
  Serial.println("setup does not run");
}

void loop() {
  Serial.println("loop does not run");
}

int main() {
  init();
  Serial.begin(9600);
  while (1) {
    Serial.println("My main is running");
    delay(1000);
  }
}

This works because main() is inside the core, which gets compiled to a ".a" library archive.  If you use any function with the same name, the linker will put your copy into the final output, rather than the one from the library.

So go ahead and use main().  The ability to do so has been there all along.  Just make sure you call init() to initialize the hardware, so things like millis() and delay() will work properly.
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Well... this

Code:
void setup() {
  Serial.begin(9600);
  Serial.println("setup does not run");
}

void loop() {
  Serial.println("loop does not run");
  pinMode(13,OUTPUT);
}

int main() {
  init();
  Serial.begin(9600);
  while (1) {
    Serial.println("My main is running");
    delay(1000);
  }
}

compiles on 0022 and not on 1.0-rc1.

I've had a quick look on the compiler/linker parameters, but can't find a difference.

Error on 1.0-rc1:

Code:
avr-gcc -Os -Wl,--gc-sections -mmcu=atmega168 -o /tmp/build792419732568248348.tmp/sketch_oct16a.cpp.elf /tmp/build792419732568248348.tmp/sketch_oct16a.cpp.o /tmp/build792419732568248348.tmp/core.a -L/tmp/build792419732568248348.tmp -lm
core.a(main.cpp.o): In function `main':
/XXX/arduino-1.0-rc1/hardware/arduino/cores/arduino/main.cpp:6: multiple definition of `main'
sketch_oct16a.cpp.o:sketch_oct16a.cpp:16: first defined here

This error vanishes when adding the 'weak' attribute as pointed out before.

I feel that if this compiles (works?) on 0022, it should do the same on 1.0
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The difference is that the pin definition data structures have been moved (through a header file) into main.cpp.
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Forgive my ignorance, but is using the 'weak' attribute for the linker to only way (correct?) to make it work again in 1.0 ?

Is the reason for the complaint that the user-provided main() is therefore not equivalent to the library one anymore?
« Last Edit: October 18, 2011, 03:14:46 pm by madworm » Logged

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The difference is that the pin definition data structures have been moved (through a header file) into main.cpp.

Why do that? In fact why not change main.cpp from:

Code:
#include <WProgram.h>

int main(void)
{
init();

setup();
   
for (;;)
loop();
       
return 0;
}

to:

Code:
void init ();
void setup ();
void loop ();

int main(void)
{
  init();
  setup();
  while (true)
    loop();
  return 0;
}

Then it compiles on its own without any header files, and will only be used if the user doesn't supply their own main function.
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Forgive my ignorance, but is using the 'weak' attribute for the linker to only way (correct?) to make it work again in 1.0 ?

That is one way.  The other way would be to move the pin definition data structures to another module.  Where they were (wiring_digital) is a good choice.  I would move them to their own module.

Quote
Is the reason for the complaint that the user-provided main() is therefore not equivalent to the library one anymore?

Someone else will have to answer that one.
« Last Edit: October 18, 2011, 03:41:20 pm by Coding Badly » Logged

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