DIY ATtiny HV UPDI Programmer - Dlloydev/jtag2updi GitHub Wiki

The firmware here supports using an ATtiny1604, 1614, 1606, 1616, 3216, 1607, 1617 or 3217 as a HV UPDI programmer. Just use a breakout board or development board for the host MCU. If you use any 5V USB serial adapter or IC with an RTS or DTR signal, an auto reset circuit and use a bootloader option in megaTinyCore, you'll be able to use the ATtiny HV programmer like a regular Arduino board to upload sketches to the target or update the programmer's firmware.

Click image to enlarge

Pin	Name	Type	Description
PA0	UPDI/RESET	Bidirectional/Input	Factory UPDI programming and Reset input, pullup enabled
PA1	Mode	Input	Mode selection, 8-bit ADC, floating input
PA2	Power Switch	Output	Enable for power switch controlling target power cycle, active high
PA3	CPP/HV Enable	Output	Charge pump power, normally low, high during HV UPDI enable pulse
PA4	CP1 charge pump	Output	Charge pump Clock 1, 413kHz during UPDI enable
PA5	CP2 charge pump	Output	Charge pump Clock 2, 413kHz during UPDI enable
PA6	LED2/HVLED	Output	Used to indicate NVM version or UPDI enable 12V pulse
PA7	LED BUILTIN	Output	Active during programming and pulses upon release of reset
PB0	UPDI target	Bidirectional	Target UPDI programming
PB1	CPS charge pump	Output	Charge pump shutdown, normally high, low during UPDI enable pulse
PB2	TX	Output	USB to serial communication to PC, TTL logic levels
PB3	RX	Input	USB to serial communication to PC, TTL logic levels

Item	Qty	Part Number	Description
1	1	ATtiny1614/1604 dev board	Arduino compatible development/breakout board with optiboot and auto-reset circuit.
2	1	Serial Adapter	Serial adapter (5V) with DTR or RTS signal
3	1	Arduino Nano HV UPDI Programmer PCB for tinyAVR 0/1	Circuit board providing 12V charge pump circuit, HV LED, mode select jumper (3 modes) and 3-pin target UPDI interface.
4	1	MIC2005A-1YM5	High-side power switch, active high enable (requires SOT23-5 adapter)

No full schematic provided as you may want to create your own custom board or prototype. Refer to the schematics and datasheets provided with your chosen components.

In the above circuit, an external resistor pullup is not required because the ATtiny's PA0 pin has an internal pullup (typical 35K). When RTS/DTR returns high, the clamping diode clamps the 10V spike from the capacitor preventing any unwanted mode change of PA0. The capacitor provides a one-shot pulse for a quick and reliable programming sequence. The reset button/resistor is optional and depends on your requirements.

JPA0	FUNCTION
REMOVED	Normal operation for uploading sketches to the target.
1-2	The RTS/DTR auto-reset circuit is connected. Used when updating firmware using a serial connection.
2-3	Used when updating firmware with another HV UPDI programmer.

Jumper	Mode	PA0 Configurations	HV Pulse	Power Cycle
REMOVED (GND)	UPDI	UPDI	NO	NO
2-3 (2.5V)	HV	UPDI, RESET	YES	NO
1-2 (5V)	PCHV	UPDI, RESET, GPIO	YES	YES

For 12V power, a charge pump IC can free up a few pins on the programmer. An alternative method would be using a switching DC-DC boost converter.

A high side power switch IC could be used for target power cycle. An alternative method would be using a high side MOSFET switching circuit.

1. Install megaTinyCore

2. In "Tools", select the board with optiboot option, chip, port, programmer and configure the UPDI pin as Reset.

3. Since this is a first time installation of the bootloader, remove the FW jumper. Now use a HV UPDI Programmer connected directly to PA0, VCC and GND and "Burn Bootloader".

4. Reinstall the FW jumper and connect serial RX, TX and RTS/DTR signals to the programmer's MCU.

5. Now you can use the serial port to Install the HV Programmer Firmware

   ● Click on the green "Clone or download" button, then select "Download ZIP".

   ● Unzip this file in a folder on your PC, then open the sketch "jtag2.updi.ino" into the Arduino IDE.

   ● Select Sketch > Upload, then disconnect the FW jumper.

You can now use the ATtiny HV UPDI Programmer to "Burn Bootloader" or to "Upload Using Programmer" to the target MCU using the Arduino IDE. Make sure to choose the appropriate board, chip and port setting for the target.