Burning a bootloader into the ATtiny3217 via the UPDI / reset pin (2)

I have made a short step by step guide for burning a bootloader into the ATtiny3217. 

The ATtiny3217 is a small Arduino compatible processor with 21 I/O lines that I use in the smallest Arduino board ever made: the Nano DIP.

MCUdude SerialUPDI programmer

SerialUPDI programmer

The MCUdude SerialUPDI programmer is a programmer for use with any AVR that has a UPDI programming interface.

• UPDI for uploading the bootloader.
• UART with USB connector for easy serial debugging.
• Automatic UART / UPDI selection. 

https://github.com/SpenceKonde/AVR-Guidance/blob/master/UPDI/jtag2updi.md

Read the article about the megaAVR ATtiny family

I want to thank Spence Konde for writing an extensive article about the megaAVR ATtiny, see GitHub.

Required

• ATtiny3217
• Arduino Nano
• 10uF capacitor
• 4.7k resistor

Step 1

Making an UPDI programmer with the Arduino Nano.

• Tools -> Board = Nano
• Tools -> Atmega328 (sometimes old bootloader)
• Upload the jtag2updi sketch to the Arduino Nano see GitHub (without the the 10uF connected!)

Step 2

Connect now the 10uF capacitor and 4.7k resistor, see the image here. 
The UPDI programmer is now ready

Step 3

Installing the megaTinyCore package.

• File -> Preferences> Additional board manager URLs = http://drazzy.com/package_drazzy.com_index.json
• Tools -> Boards -> Boards Manager ...
• Select "megaTinyCore by Spence Konde" and click "Install". (This can take a while)

See here an Arduino Nano used as UPDI programmer. If you only use this Arduino Nano now as a UPDI programmer, you can skip the steps above the next time.

Here the Small program connector for the Arduino ATtiny3217 is used because there is no USB interface.

Combined FTDI UPDI 6p

Step 4

Do this test: send the ATtiny3217-blinking-LED sketch to the ATtiny3217 board by using the UPDI programmer and the UPDI pin.
Connect the 3 pins (GND, 5V, UPDI) to the ATtiny3217 board.

• Open the sketch ATtiny3217-blinking-LED, see below
• Tools -> Board = Attiny3217 (not the w/Optiboot !)
• Chip -> ATtiny 3217
• Clock -> 16MHz internal
• UPDI/Reset Pin = UPDI (default)
• Programmer = SerialUPDI – SLOW:57600 baud
• Select Tools -> Port, select the right port
• Upload the sketch (as normal) and check if the LED is blinking

The LED on the ATtiny3217 board will continue to flash now.

Dily3217 programming with a FTDI adapter

Step 5

Burning the ATtiny3217 bootloader, after this, UPDI is not working anymore.

• Tools -> Board = ATtiny3217 (optiboot)
• Tools -> UPDI / reset pin = reset (Danger)
• Tools -> burn bootloader

The bootloader is now burned into the ATtiny3217.

Step 6

Testing if the bootloader works properly and if we can upload sketches via the serial pins RX and TX.

• Disconnect the UPDI programmer we made in step 1
• Connect an FTDI adapter between the PC and the ATtiny3217
• Tools -> Board = ATtiny 3217 (optiboot)
• Upload the ATtiny3217-blinking-LED sketch and check if the LED is blinking.

ATtiny3217-blinking-LED sketch

// File -> Preferences > Additional board manager URLs = http://drazzy.com/package_drazzy.com_index.json
const byte ledPin = 3;

void setup() 
{ pinMode(ledPin, OUTPUT);
}

void loop()
{ digitalWrite(ledPin, 0); 
  delay(500);
  digitalWrite(ledPin, 1); 
  delay(500);
}