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Digispark ATtiny85: Install and Setup. Easily save space using this tiny chip to replace an Uno. Learn how to program this chip using the standard Arduino IDE.

The Digispark ATtiny85...

...is really just an ATtiny85 with a software defined USB interface and...

  • Has 6 I/O pins.

  • Uses the Standard Arduino IDE, so it is easy to use.

  • No external chips to operate.

  • Uses an internally generated 16.5MHz clock (no need for external crystal).

  • There's no USB chip - it is all done in software!

The programming process has been tested for IDE versions (18/9/23):

1.8.19 (Reliable and old!).
2.1.0 (Very new - a completely re-designed and re-coded IDE ).

Warning: After installation it looks like the USB interface is failing. Just start the programming sequence and plug in the Digispark.

Digispark Attiny85 runs at 16.5MHz (with no external crystal) and has 6  I/O pins and connects to a USB port using a micro USB connector. The breakout board comes with an ATtiny85 chip pre-programmed with the micronucleus bootloader.

If you need to save board space and only need a few outputs the this chip is ideal. It works almost exactly the same way as an Arduino Uno (and where it doesn't there are software modules to get round missing internal modules).

For most trivial programs that you use you won't notice any difference in writing code between the ATtiny85 and the ATMega328P (Arduino Uno chip). The main difference is that the Flash is smaller in size.

Bootloader

The great thing about this bootloader is that it makes a software compatible USB interface inside the ATtiny85 - even when that chip has no USB interface. By adding support libraries into the Arduino IDE you can program this chip using the Arduino IDE system in a similar way to other Arduino microcontrollers.

The rest of this page shows you a Digispark tutorial for installing the Digispark drivers, checking that they are working correctly and programming the device.


Digistump Attiny85 breakout board

Warning: The Arduino IDE operation for the ATtiny85 is not the same as the connection operation for the Arduino - you will think that it is not working. You do not have to select a serial USB port as you do with the Arduino. It is all done on the fly. See below for details.

Digispark ATtiny85 Bootloader Timeout

The way that the Digispark Attiny85 works is to use the Window Driver to identify the Digispark but this can only be done for 5 seconds. After the 5 seconds the bootloader becomes a dumb device and the program control is transferred to the program just loaded.

Arduino IDE 1.8.8 (Windows Store 1.8.19.0)

It has been successfully programmed using Arduino 1.8.8 (Windows Store 1.8.19.0). So a bug has been corrected since 1.8.7 (I think) did not work in that IDE. Now tested on Arduino IDE 2.1.0.

Warning on Digispark operation

The interface can be finicky - I had this system working, then worked on another project and came back to the Digispark ATtiny85. The window 10 machine that had worked perfectly came up with the dreaded popup:

Warning: Even if you see these problems - the Digispark interface is entirely different to normal USB operation so. Do all the Digispark board and library installation and try to program it - it will likely work (See Step 6 below).

Warning "USB Device not recognized."

I tried the following:

  • Re-installing Digistump drivers (clicking on DPinst64 - for a 64 bit machine).
  • In device manager Deleting USB entries that correspond to the ATtiny85 by Clicking the 'View' menu entry, then show hidden devices and uninstalling the driver for those labelled "Unknown USB Device (Device Descriptor Request Failed)".
  • Using zadig to install lib32-winusb on the unknown USB Device - no effect.
  • Uninstall Arduino IDE 1.8.5 and install a custom version of it (DigistumpArduinoInstall1.5.8C.exe) - no effect. Went back to IDE 1.8.5.
Note: What actually worked was putting the USB cable into a different socket on my USB HUB with 7 extra USB ports.
Note2: On my second notebook (Windows 10). Two direct USB ports, built into the machine, came up with the "USB Device not recognised" message. Plugging a powered Hub (the same one from the other machine) allowed the Digispark to connect correctly!

In the Digispark Attiny documentation it is recommend that a powered USB hub is used so that you don't accidentally blowup the USB port in the PC.

Device Manager - Digispark Not Found

If you have a problem you'll see a message ("Unknown USB Device.") in the Windows Device Manager like this:

Device manager USB device not recognised

Device Manager - Digispark Attiny85 Driver Is Found

For successful Digispark ATtiny85 detection you will see this (message is libusb-win32 Devices, digispark bootloader - after the highlighted line "Keyboards" below). This appears after you plug in the Digispark to a USB port:

Successful ATtiny85 installation

ATtiny85 Arduino install Steps

1. Install the Arduino IDE

An easy way is to search the Microsoft Apps store in windows 8.1 or 10 and search for Arduino. Install the app. Alternatively download the executable installer here. The latest one is 1.8.8 and it does work with Digispark.

2. Install Digispark Attiny85 Windows Drivers

Download the Digispark Attiny85 windows drivers here.
(This is the 1.67 Feb 13 2016 release found here.)

Download Digistump.Drivers.zip and unzip to your hard disc. Then double click on DPinst (32 bit PC) or DPinst64 (64 bit PC) depending on your system (mine is 64bits).

Digistump Digispark Driver installation

You should now check that windows can see the Digispark - Just plug in the Digispark usb (micro usb connector) and you will hear the USB connection sound. If windows complains saying "USB Device not recognised." then you will need to fix this before going further - the IDE has nothing to do with this part.

The problem is that you have to install drivers in order for windows to correctly identify and communicate with the micronucleus device. If you have problems have a look here.

3. Set up Digistump for the IDE

To allow Digistump boards to be seen by the Arduino IDE you need to insert a line of code in the Menu > File > preferences window as shown below:

The line to insert in the "Additional Boards manager URLs" box is:

http://digistump.com/package_digistump_index.json

Click here to see contents of the package_digistump_index.json file.

If you have more than one of these lines click the double-box symbol to the right of that entry box and add each entry one per line.

Arduino IDE board seupt in preferences pane

4. Select a Digispark Board or Mode

You won't see any examples for Digistump in the Menu > File > Examples until you select the Digispark board in Menu > Tools > Boards.

From that menu select the board labelled:

Digispark (Default - 16.5MHz)

Note: The Digispark Pro is a different board that uses a bigger chip: an ATtiny167 20 pin chip (and is slightly easier to use). However once you have got the drivers going the Digispark is fairly easy to program.

Install the Digistump Boards

First click Tools > Board > Board Manager

Install Digistump Boards

Now search for the digistump board library and click install.

install digistump board library


Selecting the Digispark Board

Select Digispark 16.5MHz board

5. Select a Digispark Attiny85 Example

The examples will now be available from the Examples Menu: File > Examples > Digispark_Examples.

It does not matter which example is used, but one that does not do too much is the Infrared one - you don't need to attach an infrared receiver - you are only going to go through the process of programming it - to get used to the process. You can if you want to though - just use a standard IR receiver.

Go back to the Arduino IDE Menu > File > Examples > Digispark_Examples
And choose the Infrared example.

ATtiny85 Digispark Test with IR code example

Now you will see the following code in the Arduino IDE.

This is simple code that does not attempt to decode the IR signal it just reacts if any signal is received by flashing the built in LED. If it does not flash the LED is on pin 1 - newer boards use this as the LED pin.
int irPin=2;

void setup()
{
 pinMode(irPin,INPUT);
 pinMode(0,OUTPUT);
 //Serial.begin(9600);
 digitalWrite(0,HIGH);
     //Serial.println("You pressed a button");
     delay(1000);
     digitalWrite(0,LOW);
}

void loop()
{

  if(pulseIn(irPin,LOW))
  {
     //button pressed
     delay(100);
     digitalWrite(0,HIGH);
     //Serial.println("You pressed a button");
     delay(1000);
     digitalWrite(0,LOW);
  }

}

6. Compile and Upload a program

Leap of faith

In my new window 10 machine I re-installed all of the above and then it all appears to fail - the device manager continually alternates between device found (sound) and device disconnected (sound). Just forget all that, the programming of the Digispark is completely different to a normal Arduino device. Just start the programming sequence then plug in the Digispark to the USB cable!

Warning: After installation it looks like the USB interface is failing. Just start the programming sequence and plug in the Digispark.

There are two parts to programming the board

  1. Start the compile and upload process as you usually do for the Arduino.
  2. Plug in the Digispark ATtiny85 to initialise USB detection.

1. Normal Arduino Compilation

To start digispark attiny85 programming hit the compile and upload button or press Ctrl-u.

Once uploading starts you will see the following information in the status box at the bottom of the Arduino IDE:

Sketch uses 700 bytes (11%) of program storage space. Maximum is 6012 bytes.
Global variables use 9 bytes of dynamic memory.
Running Digispark Uploader...
Plug in device now... (will timeout in 60 seconds)
> Please plug in the device ...
> Press CTRL+C to terminate the program.

2. Micronucleus USB Detection and Upload


At this point you need to plug in (or unplug and re-plug in the Digispark Attiny85). Then you will see the following status output:

Sketch uses 700 bytes (11%) of program storage space. Maximum is 6012 bytes.
Global variables use 9 bytes of dynamic memory.
Running Digispark Uploader...
Plug in device now... (will timeout in 60 seconds)
> Please plug in the device ...
> Press CTRL+C to terminate the program.
> Device is found!
connecting: 16% complete
connecting: 22% complete
connecting: 28% complete
connecting: 33% complete
> Device has firmware version 1.6
> Available space for user applications: 6012 bytes
> Suggested sleep time between sending pages: 8ms
> Whole page count: 94  page size: 64
> Erase function sleep duration: 752ms
parsing: 50% complete
> Erasing the memory ...
erasing: 55% complete
erasing: 60% complete
erasing: 65% complete
> Starting to upload ...
writing: 70% complete
writing: 75% complete
writing: 80% complete
> Starting the user app ...
running: 100% complete
>> Micronucleus done. Thank you!

Notice that the version of micronucleus firmware is 1.6. This can be upgraded to get more space by reprogramming the bootloader.

7. Digispark LED Flash Test program

Here is a program to just flash the on-board LED. Re-program the Digispark and check the led flashes (New Digisparks have the LED on pin 1, older ones have the LED on pin 0).

Now you should be familiar with the Digispark ATtiny programming process.

#define LEDPIN 1

void setup() { pinMode(LEDPIN,OUTPUT);
} void loop() { delay(200); digitalWrite(LEDPIN,HIGH); delay(200); digitalWrite(LEDPIN,LOW);

}
[code: flash_led.ino]

Alternatively Save Bootloader Flash

To save flash memory that is used by the Digispark ATtiny85 USB bootloader you can program the chip using an AVRISP (or use an Arduino as an AVRISP) and program the chip directly through SPI. This is a bit more involved but saves you all the Flash memory used by the USB bootloader.

Conclusions

You will think that the USB interface is failing as it oscillates from (success (USB sound for good USB device) to disconnect (USB sound for bad device). It is not. Just ignore that - if you have installed the drivers and board.

Warning: After installation it looks like the USB interface is failing. Just start the programming sequence and plug in the Digispark.

All you do is start the programming sequence - then plug in the Digispark; Magically the board is  detected and programmed - try the LED flash to see it work.

Once you have got over this problem the board works easily and well with the Arduino IDE.



MCP23017 Specification

Parameter
Value
Voltage Supply (Vs)
1V8 ~ 5V5
Abs Max Voltage
-0V3 ~ 5V5
Interface
I2C
I2C Address (depends on ALT ADDR)
0x20 ~ 0x27
Interface Speed (kHz)
100, 400, 1700
Supply Current (idle): 1mA
Operational Current Max out of Vss [*] 150mA
Operational Current Max into Vdd [*] 125mA
Output current per pin 25mA
Standby Current 1uA
Operating temperature
-40°C ~ 85°C


Written by John Main who has a degree in Electronic Engineering.

Note: Parts of this page were written using chatgpt as a research assistant.

Warning: Never keep the device transmitting for more than 4ms.




Note: HMC and QMC chips output essentially the same data.


 

Note: The type uint32_t is the same type as "unsigned long".



TIP: You can find SMD chip markings here: http://www.smdmark.com


INA219

T2 text

last line




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