MKS TFT28 V2.0 / TFT32_L V3.0 — PanelDue Firmware for Klipper / Voron 2.4

Versão em Português

Hardware

Item	Value
Board	MKS TFT28 V2.0 (silk screen: MKS TFT32_L V3.0)
MCU	STM32F107VCT6 (chipid 0x418, Cortex-M3, 256 KB flash)
Display	H685, 320×240, TN normally-white
LCD controller	R61505 (ID=0x1505 read via R00h)
Touch	XPT2046 via SPI3
EEPROM	Physical I2C chip (separate from STM32 flash)
Protocol	PanelDue (based on robotsrulz/MKS-TFT)

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Flashing

Hardware required

ST-Link V2 programmer — cheap clones (~$5) work fine.

SWD wiring

Connect the ST-Link to the 6-pin JTAG header on the board (top-right corner, labeled JTAG):

Source: MKS TFT32_L V3.0 PCB schematic (bottom layer)

JTAG pin	Signal	ST-Link
1	GND	GND
2	NRST	— (not needed)
3	GND	GND
4	JTCK / SWDCLK	SWDCLK
5	+3V3	(see power note below)
6	JTMS / SWDIO	SWDIO

Power: use one source only — never two at the same time:

• Board connected to printer → connect only pins 1, 4, 6 (GND, SWDCLK, SWDIO)
• Board NOT connected to printer → also connect pin 5 (+3V3) from ST-Link, but never connect 5V (the board is 3.3V only)

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Option A — Windows (STM32CubeProgrammer)

1. Download and install STM32CubeProgrammer (free, official ST tool)
2. Connect the ST-Link to USB and to the board
3. Open STM32CubeProgrammer → select ST-LINK → click Connect
4. Go to Erasing & Programming
5. Browse to MKS-TFT32_voron24_klipper.bin
6. Set start address to 0x08000000
7. Check Verify programming and Run after programming
8. Click Start Programming

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Option B — macOS / Linux (OpenOCD)

Install OpenOCD:

# macOS
brew install openocd

# Ubuntu/Debian
sudo apt install openocd

Run in the folder where the .bin file is located:

openocd -f interface/stlink.cfg -f target/stm32f1x.cfg \
  -c "program MKS-TFT32_voron24_klipper.bin verify reset exit 0x08000000"

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Option C — From the Klipper Raspberry Pi

If the ST-Link is connected to the Pi's USB port, flash directly from the Pi (no separate computer needed):

sudo apt install openocd
cd ~
wget https://github.com/rescosta/MKS-TFT/raw/r61505-stm32f107-klipper/binaries/MKS-TFT32_voron24_klipper.bin
openocd -f interface/stlink.cfg -f target/stm32f1x.cfg \
  -c "program MKS-TFT32_voron24_klipper.bin verify reset exit 0x08000000"

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Expected output (Options B and C)

** Programming Started **
** Programming Finished **
** Verify Started **
** Verified OK **
** Resetting Target **

If you see Verified OK, the board resets automatically and the PanelDue interface appears on the display.

Important: do not use st-flash directly — it has known issues with the STM32F107 and may report success without actually flashing.

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Connecting to Klipper

1. Physical wiring

The MKS TFT28 V2.0 has a 4-pin serial connector (TTL 3.3 V) labeled EXP or RS232 on the board:

TFT28 pin	Signal	Connect to
TX	Transmit	RX of Raspberry Pi / SBC
RX	Receive	TX of Raspberry Pi / SBC
GND	Ground	GND of Raspberry Pi / SBC
5V / 3.3V	Power	(optional — can power from printer connector)

Note: TX of the TFT goes to RX of the Pi and vice-versa. TTL 3.3 V levels — do not connect to a 12 V RS232 port.

Option A — Raspberry Pi GPIO UART

Connect TX / RX / GND to the GPIO header:

Pi GPIO	Physical pin	Function
GPIO14	Pin 8	TXD (→ TFT RX)
GPIO15	Pin 10	RXD (← TFT TX)
GND	Pin 6 or 14	GND

Resulting serial device: /dev/ttyAMA0 (Pi 3/4) or /dev/ttyS0

Enable UART on the Pi if needed:

# /boot/config.txt
enable_uart=1
dtoverlay=disable-bt   # frees UART0 from Bluetooth (Pi 3/4)

Option B — USB-TTL adapter

Connect via a USB-to-serial adapter (CP2102, CH340, FTDI). The device will appear as /dev/ttyUSB0 or similar.

Identifying the correct serial port

ls /dev/tty{USB,AMA,S}*
# or
dmesg | grep tty

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2. Moonraker configuration

# moonraker.conf
[paneldue]
serial: /dev/ttyAMA0      # adjust to your detected device
baud: 57600
machine_name: Voron 2.4
macros:
  LOAD_FILAMENT
  UNLOAD_FILAMENT
confirmed_macros:
  RESTART
  FIRMWARE_RESTART

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3. printer.cfg macros

Add to printer.cfg:

# Required for PanelDue beep support
[gcode_macro PANELDUE_BEEP]
gcode:
    {% set FREQUENCY = params.FREQUENCY|default(300)|int %}
    {% set DURATION = params.DURATION|default(1.0)|float %}
    M300 S{FREQUENCY} P{(DURATION * 1000)|int}

# Optional — appear as macro buttons on the PanelDue
[gcode_macro LOAD_FILAMENT]
gcode:
    M83
    G1 E50 F300
    G1 E30 F150
    M82

[gcode_macro UNLOAD_FILAMENT]
gcode:
    M83
    G1 E10 F300
    G1 E-80 F800
    M82

If your printer has no buzzer (M300), PANELDUE_BEEP can be left empty — the PanelDue works fine without audio.

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4. Restart services

sudo systemctl restart moonraker
sudo systemctl restart klipper

The display should show "Connecting" for a few seconds, then show printer data (temperatures, position, etc.).

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R61505 register values — final configuration

Values extracted by ARM Thumb-2 disassembly of the original MKS firmware (mkstft28.bin v3.0.2).

Startup (before R01h)

Register	Value	Description
R0E5h	0x8000	R61505 proprietary startup command
R00h	0x0001	Start oscillator

Power

Register	Value	Description
R10h	0x17B0	Power Control 1: SAP=1, BT=7, APE=1
R11h	0x0037	Power Control 2: DC1=3, DC0=0, VC=7
R12h	0x0138	Power Control 3: VRH=8, PON=1, VCIRE=1
R13h	0x1700	Power Control 4: VDV=23
R29h	0x001F	VCOMH=31
R61h	0x0001	REV=1 (inverted LC drive polarity — critical for vivid colors)

R61h REV=1 is not documented in any public R61505 datasheet. It was found only by disassembly of the original MKS binary and is the key to correct color rendering on the H685 panel.

Gamma (R30h–R3Dh)

R30h=0x0707  R31h=0x0007  R32h=0x0603
R33h=0x0700  R34h=0x0202  (R61505 non-standard, undocumented)
R35h=0x0002
R36h=0x1F0F  (VRP1=31 — maximum gamma amplitude)
R37h=0x0707  R38h=0x0000  R39h=0x0000
R3Ah=0x0707  R3Bh=0x0000  (R61505 non-standard, undocumented)
R3Ch=0x0007  R3Dh=0x0000

Panel interface

R90h=0x0010  R92h=0x0000  R93h=0x0003
R95h=0x0101  R97h=0x0000  R98h=0x0000

Display turn-on sequence (R07h)

R07h=0x0021 → delay 50 ms → R07h=0x0031 → delay 50 ms → R07h=0x0173

Orientation and BGR

Parameter	Value
DisplayOrientation	ReverseX | SwapXY (0x03)
R01h	SS=0, SM=0
R03h	AM=1, BGR=1 (bit 12), I/D=11
R60h	GS=0, NL=0x27 (320 lines)

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Touch

• Controller: XPT2046 via SPI3
• Default orientation: SwapXY (0x01)
• Calibration saved to EEPROM (magicVal=0x3AB629D7)
• Calibration survives reflashing (EEPROM is not erased by mass erase)

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Backlight

• PWM via TIM4_CH3 (PD14), 1 kHz
• AFIO full remap enabled (__HAL_AFIO_REMAP_TIM4_ENABLE())
• Brightness: 100% (lcd.setBacklightBrightness(100) in Src/PanelDue.cpp)

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Building from source

Toolchain: arm-none-eabi-gcc 10.3-2021.10

# Build
make

# Flash
make flash
# or
openocd -f interface/stlink.cfg -f target/stm32f1x.cfg \
  -c "program build/MKS-TFT32.bin verify reset exit 0x08000000"

Required Makefile defines:

DEFS = -DSTM32F107xC -DMKS_TFT -DILI9328 -DR61505 -DUSE_HAL_DRIVER

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Status

Feature	State
Display orientation	✓ Correct
Touch	✓ Working (auto-calibration)
Backlight PWM	✓ Working
Klipper communication (PanelDue)	✓ Configured
Color vibrancy	✓ Vivid colors confirmed
Scan lines	✓ None