ATMEGA4809 UPDI DOWNLOAD TOOL

Version: V1.0.0  |  Author: Tom Hong  |  Date: 2026-04-24

A Windows GUI tool for flashing firmware and configuring FUSE bits on the ATmega4809 microcontroller via a SerialUPDI (HV UPDI Friend) programmer.

---

Screenshots

GUI running on Windows 10

Main Window
(connect your programmer and launch main.py)

---

Features

#	Feature	Description
1	COM Port Detection	Auto-scans all COM ports, shows VID/PID for easy CH340E identification
2	HEX File Selection	File browser, validates file size against 48 KB Flash limit
3	FUSE Configuration	Dropdown menus for BOD, Clock, Reset Pin, EEPROM, Startup Time, Bootloader
4	Write HEX	Erase → Write → Verify in one click
5	Write FUSE	Writes each FUSE byte individually with --verify
6	Write HEX & FUSE	Full flash cycle in one click
7	Chip Erase	Erase with mandatory confirmation dialog
8	Read FUSE	Reads current FUSE values from chip and maps them back to UI dropdowns
9	FUSE Preview	Live Hex byte preview updates with every dropdown change
10	Progress Bar	Animated progress indicator during any chip operation
11	Abort Button	Force-terminates the running pymcuprog process
12	Real-time Log	Color-coded output, save to .txt file

---

Hardware Requirements

Item	Specification
Programmer	HV UPDI Friend (SerialUPDI)
USB-UART chip	CH340E
Target MCU	ATmega4809
Driver	CH341SER (Windows CH340 driver)

Connection: PC → USB → CH340E → UPDI pin of ATmega4809

---

Quick Start

Option A — Portable EXE (no Python required)

Download the release package from the Releases page.

ATMEGA4809_UPDI_DOWNLOAD_TOOL_V1.0.0/
├── ATMEGA4809_UPDI_DOWNLOAD_TOOL_V1.0.0.exe   ← double-click to run
└── _internal/
    ├── pymcuprog.EXE                            ← bundled, no install needed
    └── ...

Option B — Run from source

Requirements: Python 3.10+

pip install -r requirements.txt
python main.py

Option C — Build EXE yourself

pip install pyinstaller
pyinstaller ATMEGA4809_UPDI_DOWNLOAD_TOOL.spec --clean -y

Output will be in dist/ATMEGA4809_UPDI_DOWNLOAD_TOOL_V1.0.0/.

---

FUSE Reference (ATmega4809 Datasheet Section 7.8)

Offset	Register	Default	Description
0x00	WDTCFG	0x00	Watchdog Timer — disabled
0x01	BODCFG	0x54	BOD 2.6 V, Active=Enabled, Sleep=Disabled
0x02	OSCCFG	0x02	Internal 20 MHz oscillator
0x05	SYSCFG0	0xC8	CRC=disabled, PF6=RESET pin, EESAVE=0
0x06	SYSCFG1	0x07	Startup time = 64 ms
0x07	APPEND	0x00	No application partition
0x08	BOOTEND	0x00	No bootloader partition

SYSCFG0 bit layout: CRCSRC[7:6]=11 (fixed) | RSTPINCFG[3] | EESAVE[0]

Note: RSTPINCFG controls PF6 only.
The UPDI interface lives on a separate pin (PF0) and is always available regardless of this setting.

---

Project Structure

├── main.py                          # Entry point
├── config.py                        # Constants, FUSE option definitions
├── requirements.txt
├── ATMEGA4809_UPDI_DOWNLOAD_TOOL.spec  # PyInstaller build config
├── gui/
│   ├── main_window.py               # Main window layout
│   ├── fuse_panel.py                # FUSE settings panel
│   └── log_panel.py                 # Log output widget
├── backend/
│   ├── burner.py                    # pymcuprog subprocess wrapper + abort
│   ├── fuse_calculator.py           # FUSE option → byte value mapping
│   └── port_scanner.py              # COM port enumeration
└── assets/                          # Icons and resources

---

Known Limitations

• Windows only — COM port naming and paths are Windows-specific.
• pymcuprog baud rate flag is -c (--clk), not -b (--bytes). Mixing them causes a "115200 bytes outside boundary" error.
• FUSE writes are per-byte — pymcuprog does not support batch FUSE writes; each offset is written individually.
• The portable EXE's _internal/ folder must stay alongside the .exe file.

---

Dependencies

Package	Version	Purpose
customtkinter	≥ 5.2.0	Modern Tkinter UI
pyserial	≥ 3.5	COM port enumeration
pymcuprog	≥ 3.19.0	UPDI programming backend

---

License

This project is licensed under the MIT License.

---

Changelog

Version	Date	Notes
V1.0.0	2026-04-24	Initial release — full feature set, PyInstaller portable build