Beginning programming for Atmel uProcessors

arduinoatmelmicrocontroller

I'm taking the next step, going from my Netduino into the smaller microcontrollers from ATMEL (since there is no really tiny (tinier than the netduino) stuff running .NET).

Also have some experience with ATML and some (silly) assembly coding back from when I went to college. Assembly isn't my thing, my minimum requirement is C.

I'm looking at the ATTiny84 and ATTiny85 microcontrollers.

Since I don't have a Arduino Uno or whatever, I would need a programmer. The Atmel AVRISP STK500 USB ISP Programmer should do, but is there anything else I need to program the microcontrollers?

The plan is to put it in a breadboard, connect the programmer to the microscontroller and AVR Studio should do the rest?

Now there is some stuff I don't understand. Is it optional to put a bootloader on it? As I understand it you can put Arduino bootloader on both of them, making them able to run Arduino stuff which in turn could simplify the programming?

What is the process here, do I use the AVR Studio to flash both of the microcontrollers with Arduino tiny and then do the rest of the programming in Arduino?

Best Answer

Based on your intent to use AVR Studio, I will assume you are wanting to develop in a Windows environment. Most of my recommendations below are portable to unix-y systems as well.

You should do the following:

Download / Install WinAVR
Download Eclipse IDE for C/C++ Developers
Follow instructions to install the AVR-Eclipse plugin.
Make a new project targetting your desired chip and get a blinking light working. Proceed to more advanced things from there.
You can use AVR Studio to target your chip with a hex file, or you can use avrdude to do it from the command line (the programmeres you suggested should both be viable in either case)

The concept of using a bootloader with an ATtiny is not a great idea, imho. You'll need additional support circuitry to do that (a USB to Serial converter and associated reset circuitry at least), and there is certainly some software complexity involved, as the ATtiny's don't generally have bootloader support built-in (no BOOTRST fuse for example). And you are typically already very space limited as it is.

Related Solutions

Electronic – arduino – How to burn arduino mega 2560 bootloader

You should be able to burn it using the Arduino software with the AVR ISP. See the Tools menu.

If that doesn't work, try the Arduino forum.

Electronic – Arduino/Atmel Output Assembly

The AVR, like most microcontrollers, uses memory-mapped IO. In a nutshell, this means that a part of the memory space of the microcontroller is reserved for the peripherals. When you change a bit in this area of memory, you're not sending a signal to change a bit of memory, you're sending a signal to change the value of a peripheral.

To understand the details of how this works on your AVR, the Special Function Registers section of AVR-libc (and, more importantly, sfr_defs.h and iom328p.h) are recommended reading.

[Warning: Technical writing ahead, pay close attention] For example, PORTB is defined as _SFR_IO8(0x05) in iom328p.h. In sfr_defs.h, _SFR_IO8(io_addr) is defined as _MMIO_BYTE((io_addr) + __SFR_OFFSET). __SFR_OFFSET is 0x20, the location just after the registers. The space after this address and before RAMSTART (0x100) is used for the peripherals. Going back to our example, _MMIO_BYTE(mem_addr) is defined as (*(volatile uint8_t *)(mem_addr)). Therefore, when you write PORTB, you're really writing *(volatile uint8_t *)(0x25), which defines a byte-wide pointer to the location in memory 0x25. [/Warning]

So, when (in C) you write PORTB |= 0x01, you're really writing the value 1 to the peripheral at byte 0x25, or port B pin 0. If this pin is configured as output (using DDRB, which is at 0x24), PORTB |= 0x01 will cause port B pin 0 to go high. Phew!

So, if you use the assembly instructions (SBI - Set Bit in I/O Register):

sbi  0x24,1 ;Data direction set to output
sbi  0x25,1 ;Set port B pin 0 high

You'll set the pin high.

Of course, use inline assembler with GCC and #include <avr/io.h> to get the conventional names and simplify your task.

Note that all of the peripherals use this scheme, not just the IO pins. Read iom328p.h if you're interested in the locations of other peripherals.

Best Answer

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Electronic – arduino – How to burn arduino mega 2560 bootloader

Electronic – Arduino/Atmel Output Assembly

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