Having written a basic blink program in C for my ATtiny85 with a USBtinyISP (Part 1), I wanted to use it to control other types of hardware. That meant I wanted to be able to use Arduino libraries.
The Arduino IDE
I normally use Makefiles, but the Arduino IDE is much better supported so I tried that first. I followed the steps at High-Low Tech: Programming an ATtiny w/ Arduino 1.6 (or 1.0). But the short summary is:
- Run the Arduino IDE
- In "Additional Boards Manager" near the bottom, paste this:
and click OK
- Tools->Boards->Board Manager...
- Find the ATTiny entry, click on it, and click Install
- Back in the main Arduino IDE, Tools->Boards should now havea
couple of Attiny entries. Choose the one that corresponds to your
ATTiny; then, under Processor, narrow it down further.
Now you should be able to Verify and Upload a blink sketch just like you would to a regular Arduino, subject to the pin limitations of the ATTiny.
That worked for blink. But it didn't work when I started adding libraries. Since the command-line was what I really cared about, I moved on rather than worrying about libraries just yet.
ATtiny with Arduino-Makefile
For most of my Arduino development I use an excellent package called Arduino-Makefile. There's a Debian package called arduino-mk that works fine for normal Arduinos, but for ATtiny, there have been changes, so use the version from git. A minimal blink Makefile looks like this:
BOARD_TAG = uno include /usr/share/arduino/Arduino.mk
It assumes that if you're in a directory called blink, it
should compile a file called blink.ino. It will also build
any additional .cpp files it finds there.
uploads the code to a normal Arduino.
With Attiny it gets quite a bit more complicated. The key is that you have to specify an alternate core:
ALTERNATE_CORE = ATTinyCore
But there are lots of different ATtiny cores, they're all different, and they each need a different set of specifiers like BOARD_TAG in the Makefile. Arduino-Makefile comes with an example, but it isn't very useful since it doesn't say where to get the cores that correspond with the various samples. I ended up filing a documentation bug and exchanging some back-and-forth with the maintainer of the package, Simon John, and here's what I learned.
First: as I mentioned earlier, you should use the latest git version of Arduino-Makefile. The version in Debian is a little older and some things have changed; while the older version can be made to work with ATtiny, the recipes will be different from the ones here.
Second, the recipes for each core will be different depending on which version of the Arduino software you're using. Simon says he sticks to version 1.0.5 when he uses ATtinys, because newer versions don't work as well. That may be smart (certainly he has a lot more experience than I do), but I'm always hesitant to rely on software that old, so I wanted to get things working with the latest Arduino, 1.8.5, if i could, so that's what the recipes here will reflect.
Third, as mentioned in Part 1, clock rate should be 1MHz, not 8MHz
as you'll see in a lot of web examples, so:
F_CPU = 1000000L
Fourth, uploading sketches. As mentioned in the last article, I'm using
a USBtinyISP. For that, I use
ISP_PROG = usbtiny and
sketches are uploaded by typing
make ispload rather than
make upload. change that if you're usinga
With those preliminaries over: I ended up getting two different cores working, and there were two that didn't work. Install the cores in subdirectories in your ~/sketchbook/hardware directory. You can have multiple cores installed at once if you want to test different cores. Here are the recipes.
This is the core that Simon says he prefers, so it's the one I'm going to use as my default. It's at https://github.com/Coding-Badly/arduino-tiny.git, and also a version on Google Code. (Neither one has been updated since 2013.)
git clone it into your sketchbook/hardware.
cp 'Prospective Boards.txt' boards.txt
or create a new boards.txt and copy from 'Prospective Boards.txt'
all the boards you're interested in (for instance, all the attiny85
definitions if attiny85 is the only attiny board you have).
Then your Makefile should look something like this:
ARDUINO_DIR = /path/to/arduino-1.8.5 BOARD_TAG = attiny85at8 ALTERNATE_CORE = tiny F_CPU = 1000000L ISP_PROG = usbtiny include /path/to/Arduino-Makefile/Arduino.mk
If your Arduino software is installed in /usr/share/arduino you can omit the first line.
Now copy blink.ino -- of course, you'll have to change pin 13
to be something between 1 and 6 since that's how many pins an ATtiny
has -- and try
This core is at https://github.com/SpenceKonde/ATTinyCore.git. I didn't need to copy boards.txt or make any other changes, just clone it under sketches/hardware and then use this Makefile:
ARDUINO_DIR = /path/to/arduino-1.8.5 ALTERNATE_CORE = ATTinyCore BOARD_TAG = attinyx5 BOARD_SUB = 85 F_CPU = 1000000L ISP_PROG = usbtiny include /path/to/Arduino-Makefile/Arduino.mk
There are plenty of other ATtiny cores around. Here are two that apparently worked once, but I couldn't get them working with the current version of the tools. I'll omit links to them to try to reduce the probability of search engines linking to them rather than to the more up-to-date cores.
Damellis's attiny (you may see this referred to as HLT after the domain name, "Highlowtech"), on GitHub as damellis/attiny, was the first core I got working with Debian's older version of arduino-mk and Arduino 1.8.4. But when I upgraded to the latest Arduino-Makefile and Arduino 1.8.5, it no longer worked. Ironic since an older version of it was the one used in most of the tutorials I found for using ATtiny with the Arduino IDE. Simon says this core is buggy: in particular, there are problems with software PWM.
I also tried rexxar-tc's arduino-tiny.core2 (also on GitHub). I couldn't get it to work with any of the Makefile or Arduino versions I tried, though it may have worked with Arduino 1.0.
With two working cores, I can get an LED to blink. But libraries are the point of using the Arduino framework ... and as I tried to move beyond blink.ino, I found that not all Arduino libraries work with ATtiny. In particular, Wire, used for protocols like I2C to talk to all kinds of useful chips, doesn't work without substantial revisions. But that's a whole separate topic. Stay tuned.
[ 19:06 Nov 29, 2017 More hardware | permalink to this entry | ]