To use an Arduino board as an ISP programmer, simply upload the Arduino IDE example sketch named “ArduinoISP”. Next, connect the SPI pins of the Arduino board to the MCU chip or MCU board to be programmed. Then, you can start using the Arduino board as an ISP programmer.

To illustrate the steps for the procedure, first, I will make an Arduino Nano board into an ISP programmer. Then, I will show how to upload sketches and burn bootloaders to a Digispark ATtiny85 development board.

Step by Step Guide on How to Use Arduino as ISP Programmer

STEP 1 – Connect your Arduino board to your computer’s USB port.

Connect the Arduino board of your choice to your programming computer hosting the Arduino IDE. In the next several steps, we will upload the ArduinoISP sketch to the board to make it an ISP programmer.

STEP 2 – Open your Arduino IDE and open the ArduinoISP sketch.

Open your Arduino IDE. If you are a beginner and you have not yet installed the Arduino IDE, please see How to Install Arduino IDE on Windows 10. On the Main menu, select File/Examples/11.ArduinoISP/ArduinoISP.

You should see the screen shown below after clicking on the ArduinoISP on the Built-in Examples menu.

STEP 3 – Choose the name of your Arduino board from the Board Manager’s list.

Go to Tools/Board/Arduino AVR Boards and select the type of Arduino board you are using. As shown in the screenshot below, I chose Arduino Nano for my Arduino board.

STEP 4 – Set the proper COM serial port for your board.

On the Tools menu, select Port. Then select from the serial ports list the appropriate port for your Arduino board.

STEP 5 – Click the Upload button.

As a final step for uploading the ArduinoISP sketch to the Arduino board, click on the Upload button.

When you see the message “Done uploading”, congratulations!!! You now have a full-pledged ISP programmer.

In the following steps, we are going to show how to use the Arduino board acting as an ISP programmer to:

• Program or upload a sketch to a Digispark ATtiny85 board
• Burn an Optiboot bootloader
• Burn a Micronucleus bootloader

STEP 6 – Connect the ISP programmer (the Arduino board) to the Digispark ATtiny85 development board.

Like in any other ISP programmers, including the popular USBtinyISP and USBasp programmers, we use six (6) terminals of the ISP programmer to connect to the device to be programmed. These terminals are:

• MOSI
• MISO
• SCLK
• RESET
• VCC
• GND

On the Arduino board acting as an ISP programmer, the corresponding terminals are as follow:

• D11 (MOSI) —> MOSI
• D12 (MISO) —> MISO
• D13 (SCLK) —> SCLK
• D10 (SS) —> RESET
• 5V —> VCC
• GND —> GND

Now, based on the foregoing discussion, we can connect the Arduino board to the Digispark ATtiny85 board using the following terminals:

Arduino Board —> Digispark ATtiny85 Board
D11 (MOSI) —> PB0(MOSI)
D12 (MISO) —> PB1(MISO)
D13 (SCLK) —> PB2(SCLK)
D10 (SS) —> PB5(RESET)
5V —> 5V
GND —> GND

For reference purposes, the Digispark ATtiny85 development board pinout is shown below. For more information on Digispark ATtiny85, you may consult the Digispark ATtiny85 Pinout and Configuration.

Shown below is the Fritzing breadboard diagram for connecting the Arduino Nano board to the Digispark ATtiny85 board.

How to connect the Arduino Nano board to the Digispark ATtiny85 board illustrated by an old-school schematic diagram.

After connecting the Arduino board to the Digispark ATtiny85 board, we are now ready to test drive the Arduino board as an ISP programmer.

Since we are going to work with the Digispark ATtiny85 board, you must have the board core ATTinyCore by Spence Konde installed on your Arduino IDE. If you do not have the ATTinyCore installed yet, see the article How to Install ATTinyCore on Arduino IDE.

STEP 7 – Copy and Paste the Blink Program.

Going back to the Arduino IDE, create a new sketch and then copy and paste the Blink program sketch shown below.

/*
www.cyberblogspot.com
07Jan2022  
*/

#define LED_BUILTIN 1  //PB1 for Model A
                       //PB0 for Model B

void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
}

STEP 8 – Change the board from Arduino board to Digispark ATtiny85 board.

Go to Tools/Board/ATTinyCore and select ATtiny25/45/85 (No bootloader). Take note that we are using the “No bootloader” option and NOT the “Micronucleus/Digispark” option. This is because we are going to upload the Blink sketch via an ISP programmer (the Arduino board) and not thru the Digispark’s USB port.

STEP 9 – Select the proper COM port.

Go to Tools/Port and choose the correct COM port from the ports list.

STEP 10 – Select the programmer type.

On the Tools/Programmer menu, select Arduino as ISP as the programmer type.

STEP 11 – Upload the Blink program.

Upload the Blink program by clicking on the Upload button.

When you see the message saying that the upload is done, your Digispark ATtiny85 board should start blinking the built-in LED.

How to Burn Bootloader on Digispark ATtiny85 Using Arduino as ISP Programmer

Burn Optiboot Bootloader

STEP 1 – Select ATtiny45/85 (Optiboot) from the ATtinyCore list.

STEP 2 – Verify that the proper COM port is selected.

STEP 3 – Make sure that the programmer selected is “Arduino as ISP”.

STEP 4 – Click “Burn bootloader” to start the burning process.

Burn Micronucleus Bootloader

To burn the Micronucleus bootloader onto the Digispark ATtiny85 board using the Arduino as ISP programmer, follow the steps above for burning the Optiboot bootloader. However, instead of selecting ATtiny45/85 (Optiboot), select ATtiny85 (Micronucleus / Digispark) from the ATtinyCore list of supported devices.

References on How to Use Arduino as ISP Programmer

In-System Programming (ISP)
How to Install ATTinyCore on Arduino IDE
How to Program ATtiny85 with Arduino IDE
Digispark ATtiny85 Pinout and Configuration
How to Program Digispark ATtiny85 Board with Arduino IDE
Digispark USB Device Not Recognized
How to Use AT-09 BLE with Arduino and Smartphone

The post How to Use Arduino as ISP Programmer appeared first on CyberBlogSpot.

Types of Digispark Boards

Figure 1 shows the two (2) popular versions of the Digispark ATtiny85 development boards. The one on the left uses a type-A USB connector to connect directly to the USB port of a PC or a laptop. On the other hand, the board on the right has a micro-USB connector. As a result, we need a micro-USB cable to connect this to a computer for programming purposes.

It should be observed that both boards have the same pin layout. We can breadboard them as long as we do not connect a header pin to the VIN terminal.

Figure 2 is a picture of another type of Digispark ATtiny85 board. As shown in the picture, the board does not have an ATtiny85 chip but instead only an 8-pin DIP socket. We must provide a DIP-type ATtiny85 chip in order to use this board. Also, the pin layout of this board is different. This board is not breadboard friendly. However, the pin layout is ICSP-programmer ready. That is, the pins are arranged so as to accept the female connector of an AVR ICSP-programmer.

It must be mentioned here that technically, this board is not (yet) a Digispark ATtiny85 board. A Digispark ATtiny85 board has an ATtiny85 chip that was burned with a Micronucleus bootloader. In order to make this board a Digispark board, it needs an ATtiny85 chip that was pre-programmed with a Micronucleus bootloader. Otherwise, an ATtiny85 without a bootloader can be inserted into the DIP socket and an ICSP programmer is used to burn a new Micronucleus bootloader into it.

Digispark ATtiny85 Specifications

• Support for the Arduino IDE 1.0+ (OSX/Win/Linux)
• Power via USB or External Source – 5v or 7-35v (12v or less recommended, automatic selection)
• On-board 500ma 5V Regulator
• Built-in USB
• 6 I/O Pins (2 are used for USB only if your program actively communicates over USB, otherwise you can use all 6 even if you are programming via USB)
• 8k Flash Memory (about 6k after bootloader)
• I2C and SPI (vis USI)
• PWM on 3 pins (more possible with Software PWM)
• ADC on 4 pins
• Power LED and Test/Status LED

Digispark ATtiny85 Pinout

Digispark ATtiny85 Pinout Description

ATtiny85 Breakout

First of all, by referring to Figure 3, you will notice that the Digispark board serves as a breakout board for the ATtiny85 chip. All of the eight pins of the ATtiny85 chip are accessible. The physical pins of the ATtiny5 chip are designated by the gray-colored pinouts numbered 1 to 8.

Six (6) Digital I/O Pins

As per specification, the Digispark ATtiny85 board can be configured to use six (6) digital I/O ports. These ports are shown in Figure 3 as yellow pins, labeled PB0 to PB5. NOTE: Port B pin PB5 is by default configured as a RESET pin. In order to use PB5 as an I/O port, an ATtiny85 fuse (RSTDISBL) has to be reset (changed from 1 to 0). Please see How to Reset ATtiny85 Fuses.

Arduino IDE Programming Notes

In the Arduino IDE, pins PB0 to PB5, when used as digital I/O are referred to as 0 to 5. That is,

/*
cyberblogspot.com 09Jan2023
*/

bool a, b, c;

void setup() {
  // put your setup code here, to run once:
  pinMode(0, INPUT);   //set PB0 as input
  pinMode(1, INPUT);   //set PB1 as input
  pinMode(2, INPUT);   //set PB2 as input
  pinMode(3, OUTPUT);  //set PB3 as output
  pinMode(4, OUTPUT);  //set PB4 as output
  pinMode(5, OUTPUT);  //set PB5 as output
}

void loop() {
  // put your main code here, to run repeatedly:
  a = digitalRead(0);     //read PB0
  b = digitalRead(1);     //read PB1
  c = digitalRead(2);     //read PB2
  digitalWrite(3, LOW);   //set PB3 LOW
  digitalWrite(4, LOW);   //set PB4 LOW
  digitalWrite(5, HIGH);  //set PB5 HIGH
}

Four (4) Analog to Digital Converter (ADC) Ports

Port B ports PB2 to PB5 can be configured as analog inputs. These pins are shown in Figure 3 as orange pins. The pins are labeled ADC0 to ADC3. Be aware that the Port B numbers do not exactly match the ADC port numbers. In other words, PB2 does not correspond ADC2, PB3 does not correspond to ADC3, and so on. Instead,

• ADC0 is PB5
• ADC1 is PB2
• ADC2 is PB4
• ADC3 is PB3

Arduino IDE Programming Notes

When using the command analogRead(), Arduino IDE assumes you are using the ADC port numbers (0 for ADC0, 1 for ADC1, 2 for ADC2, and 3 for ADC3) and NOT the Port B numbers (0 for PB0, 1 for PB1, 2 for PB2, 3 for PB3, 4 for PB4, and 5 for PB5). However, the pinMode() command expects you to use the Port B numbers. This is one of ATtiny85’s peculiarities that is very confusing. The example code below should clear this up.

/*
cyberblogspot.com 09Jan2023
*/

int a, b, c, d;

void setup() {
// put your setup code here, to run once:
// the following four lines of code are actually not needed
// because by default the I/O pins are in Hi-Z INPUT mode
pinMode(2, INPUT); //set PB2 as input
pinMode(3, INPUT); //set PB3 as input
pinMode(4, INPUT); //set PB4 as input
pinMode(5, INPUT); //set PB5 as input
}

void loop() {
// put your main code here, to run repeatedly:
a = analogRead(0); //read ADC0 which is in PB5
b = analogRead(1); //read ADC1 which is in PB2
c = analogRead(2); //read ADC2 which is in PB4
d = analogRead(3); //read ADC3 which is in PB3
}

Three (3) Pulse Width Modulation (PWM) Outputs

Referring again to Figure 3, there are three (3) PWM outputs available on Digispark ATtiny85 boards. These are colored green in the pinout shown above and are labeled as PWM0, PWM1, and PWM4. There is no typo error here. The third PWM output is labeled as PWM4 because the PWM port numbers use the same Port B numbers. To clarify,

• PWM0 is PB0
• PWM1 is PB1
• PWM4 is PB4

Arduino IDE Programming Notes

The PWM output signal is generated by the command analogWrite(). Although we are going to use the ports as analog outputs, we DO NOT use the ADC port numbers. Rather, we use the PWM port numbers which are the same as the Port B numbers. In other words, we are also using the Port B numbers in programming PWM in the Arduino IDE. Please take a look at the following sketch.

/*
cyberblogspot.com 09Jan2023
*/

void setup() {
  // put your setup code here, to run once:
  pinMode(0, OUTPUT);  //set PB0 (PWM0) as output  
  pinMode(1, OUTPUT;  //set PB1 (PWM1) as output
  pinMode(4, OUTPUT);  //set PB4 (PWM4) as output
}

void loop() {
  // put your main code here, to run repeatedly:
  analogWrite(0, 255);  //100% duty cycle PWM on PB0
  analogWrite(1, 128);  //50% duty cycle PWM on PB1
  analogWrite(4, 0);    //0% duty cycle PWM on PB4
}

SPI (Serial Peripheral Interface) Communication

Ports PB0, PB1, and PB2 can be used for SPI communication:

• MOSI – PB0
• MISO – PB1
• SCLK – PB2

I²C (Inter-Integrated Circuit) Communication

Ports PB0 and PB2 can be used for I2C communication:

• SDA – PB0
• SCK – PB2

USB (Universal Serial Bus) Communication

Ports PB3 and PB4 can be used for USB communication:

• USB- is PB4
• USB+ is PB3

Pin Change Interrupt and External Interrupt

Finally, ports PB0 to PB5 can all be used for pin change interrupt and PB2 as external interrupt pin.

Final Notes on Port B Pins

PB5 has limited current sourcing capacity. Also, when it is at output HIGH, it generates 3V instead of 5V on its output.

PB3 and PB4 are both used during programming (sketch upload). Therefore, it may be necessary to temporarily disconnect the circuits connected to them to avoid interfering with the uploading of sketches. Additionally, PB3 has a 1.5K pull-up resistor that is used for USB communication.

PB0 or PB1 has the built-in LED attached to it. Version A boards use PB1 while version B boards use PB0.

Digispark ATtiny85 Schematic Diagram

References on Digispark ATtiny85 Pinout and Configuration

http://digistump.com/wiki/digispark
ATtiny85 External and Pin Change Interrupt
How to Install Arduino IDE on Windows 10
How to Install ATTinyCore on Arduino IDE
How to Program ATtiny85 with Arduino IDE
How to Program Digispark ATtiny85 Board with Arduino IDE
Digispark USB Device Not Recognized
How to Use AT-09 BLE with Arduino and Smartphone

The post Digispark ATtiny85 Pinout and Configuration appeared first on CyberBlogSpot.