Flip Display

The NanoVNA-H display can be rotated 180 degrees to accommodate different mounting orientations or user preferences. The flip affects the LCD, touch input, and jog wheel simultaneously.

Why Flip the Display

• Device mounted upside down in an enclosure or on a stand
• Preferred viewing angle (USB cable running up vs down)
• After screen replacement with different ribbon cable orientation
• Accessibility — positioning the SMA connectors on a more reachable side

Flip Display via Menu

1. Tap the screen to open the menu
2. Navigate to CONFIG
3. Tap FLIP DISPLAY
4. The display immediately rotates 180 degrees

Note

The menu disappears during the flip because the firmware triggers a full screen redraw — clearing the screen, redrawing all traces, the frequency bar, battery icon, and calibration status. Tap the screen again to reopen the menu.

Save the Setting

To make the flip permanent:

1. After flipping, go to CONFIG
2. Tap SAVE or use shell command saveconfig

Without saving, the display returns to default orientation on power cycle.

Caution

The flip state is stored as a bit in config._vna_mode, the same bitfield that holds search mode, grid style, and other toggle settings. If you recall a saved calibration slot that was created before flipping, it will not overwrite the flip setting — mode bits are preserved separately from calibration data. However, a full config reset will clear the flip.

What Happens When You Flip

The firmware coordinates four subsystems when you toggle flip:

LCD Hardware Rotation

The LCD controller (ILI9341, ST7789, or ST7796S) receives a MADCTL (Memory Access Control) register write that changes the pixel scan direction. This is a hardware-level rotation — the controller reads its frame buffer in the opposite order, so no CPU cycles are spent rearranging pixels. The firmware stores a lookup table of MADCTL values for each LCD type and rotation:

DISPLAY_ROTATION_0   → Normal scan order
DISPLAY_ROTATION_180 → MX + MY flags set (mirror both axes)

Different LCD controllers use different MADCTL bit patterns for the same visual rotation. The firmware auto-detects the LCD type at startup and indexes the correct lookup table entry.

Touch Coordinate Inversion

When flip mode is active, the firmware inverts touch coordinates after the normal calibration transform:

tx = LCD_WIDTH  - 1 - tx
ty = LCD_HEIGHT - 1 - ty

This happens transparently — every touch event is remapped so tapping the upper-left corner still registers as upper-left, regardless of physical orientation.

Touch Calibration Point Swap

Touch calibration (CONFIG > TOUCH CAL) asks you to tap two corner targets: upper-left and lower-right. When the display is flipped, the firmware swaps which calibration storage slots receive which point. This ensures the calibration data is stored correctly even though the physical screen is rotated.

If you flip the display after calibrating, the existing calibration data remains valid — the coordinate inversion handles the remapping. You only need to recalibrate if touch accuracy feels off.

Jog Wheel Direction Swap

The hardware jog wheel (lever) uses two GPIO lines for left and right rotation. When flip mode is active, the firmware swaps these bits so that turning the wheel clockwise still moves markers to the right (higher frequency) even though the physical device is upside down.

Default Orientation

Model	Default USB Position	Default SMA Position
NanoVNA-H	Top edge	Bottom edge
NanoVNA-H4	Side edge	Opposite side

“Default” means DISPLAY_ROTATION_0 — the orientation programmed into the LCD initialization sequence.

Shell Command

The flip is controlled through the config command, which manages all VNA mode toggle bits:

# Enable display flip
config flip 1

# Disable display flip (return to normal)
config flip 0

# Save so it persists across power cycles
saveconfig

The config command accepts 0 (clear bit) or 1 (set bit). There is no query form — if you need to check the current flip state, look at the display orientation or check config._vna_mode in a memory dump.

Note

The config command also controls other mode toggles. Run config with no arguments to see the full list for your firmware version (typically: auto, avg, connection, mode, grid, dot, bk, flip, separator).

Practical Scenarios

Desktop Stand (USB at Bottom)

For a tilting stand where the USB cable exits downward:

1. Place device in stand with USB connector at the bottom
2. The display will appear upside down
3. Go to CONFIG > FLIP DISPLAY
4. Save with CONFIG > SAVE

Panel Mount in Enclosure

When mounting the NanoVNA-H behind a panel cutout:

1. Determine the required physical orientation for your enclosure
2. Mount the device
3. If the display is inverted, flip it via menu or shell
4. Save configuration

Replacement LCD Module

Some aftermarket LCD modules have the ribbon cable on the opposite side, resulting in a 180-degree rotated image:

1. Install the new LCD module
2. Power on — if the display is upside down, the module has opposite scan direction
3. Flip the display via CONFIG > FLIP DISPLAY
4. Run CONFIG > TOUCH CAL to calibrate touch for the new panel
5. Save configuration

Tip

If the replacement LCD uses a different controller (e.g., ST7789 instead of ILI9341), the firmware auto-detects it during initialization. The flip feature works identically across all supported controllers.

Troubleshooting

Can’t Navigate Menu (Display Upside Down)

If the display is inverted and touch coordinates don’t match:

1. Connect via USB serial terminal (115200 baud)
2. Type config flip 1 and press Enter
3. The display flips immediately
4. Type saveconfig to persist

This is the most common reason to use the shell command — the touch screen is unusable when the display is flipped but the touch coordinates are not.

Touch Feels Offset After Flipping

The coordinate inversion should handle this automatically. If touch accuracy is poor:

1. Go to CONFIG > TOUCH CAL
2. Tap the two calibration targets accurately
3. Save configuration

The calibration procedure accounts for the current flip state — it swaps the calibration point storage order so the data is correct.

Jog Wheel Moves Marker Wrong Direction

This should not happen — the firmware swaps the lever GPIO bits when flip mode is active. If it does occur:

• Verify the firmware version supports __FLIP_DISPLAY__ (all recent DiSlord-based firmware does)
• Try toggling flip off and on again
• Power cycle the device

Flip Doesn’t Persist After Power Off

The flip state is stored in config._vna_mode, which lives in flash memory. If it doesn’t persist:

1. Make sure you ran saveconfig (or CONFIG > SAVE) after flipping
2. Check that flash save completed — the device briefly pauses during save
3. If the device has flash corruption, a full reset and reconfiguration may be needed

Feature Flag

The flip display feature is compiled conditionally under the __FLIP_DISPLAY__ flag in nanovna.h. All current production firmware includes this flag. If you are building custom firmware and the FLIP DISPLAY menu item is missing, ensure this define is present:

#define __FLIP_DISPLAY__

Related Settings

• Touch Calibration (CONFIG > TOUCH CAL): May improve accuracy after flipping
• Brightness (CONFIG > BRIGHTNESS): Viewing angle changes may benefit from brightness adjustment
• Grid Style (config grid / config dot): Visual preference toggles stored in the same mode bitfield