Lo-tech RPi VGA Adapter

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Lo-tech-VGA-interface-board-mounted.jpg

The Lo-tech RPi VGA Adapter is a high-quality display board that provides second-screen capabilities to Raspberry Pi boards equipped with 40-pin GPIO header. The two screens can be connected concurrently and used independently, and are both powered directly by the RPi’s GPU and so achieve the same graphics performance.

Key Features:

  • VGA Interface for RaspberryPi SBCs with 40-pin GPIO header (Model A+, B+, 2, and 3)
  • Standard VGA DSUB connector, supports all video modes up to 1080p
  • Resistor ladder type DAC, with 8-bit resolution on each channel (888 format)
  • Buffered H-Sync and V-Sync ensures all GPIOs operate within their design current rating
  • ESD protection to IEC−61000−4−2 Level 4
  • Natively supported in Raspbian Jessie via dpi24.dtb overlay
  • Can be used as primary display or as a second (independent) display in addition to the on-board HDMI output

The board has been designed to fit directly on top of the RaspberryPi following the HAT physical dimensions (this board does not however provide the I2C EEPROM function required for HAT auto-configuration).

This product is available as a bare PCB and and assembled product via the site store.

Contents

Raspbian Configuration

Raspbian Jessie provides native support for the parallel display interface provided via the GPIO header with alternate mode 2 via an overlay. This can be enabled via config.txt on the boot partition,

dtoverlay=dpi24
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=16
dpi_output_format=0x17

Monitor resolution is determined by dpi_mode parameter:

dpi_mode value Resolution Frequency
4 640x480 60Hz
9 800x600 60Hz
16 1024x768 60Hz
21 1152x864 75Hz
23 1280x768 60Hz
28 1280x800 60Hz
32 1280x960 60Hz
35 1280x1024 60Hz
39 1360x768 60Hz
42 1400x1050 60Hz
47 1440x900 60Hz
51 1600x1200 60Hz
58 1680x1050 60Hz
69 1920x1200 60Hz
81 1366x768 60Hz
82 1920x1080 (1080p) 60Hz
85 1280x720 (720p) 60Hz

Note that, at time of writing, the Raspbian X Desktop is not extended across displays. omxplayer can however play video on one screen whilst working on the other, for example:

  • To play on VGA device when desktop is on HDMI device: omxplayer --display 4 test.mp4
  • To play on HDMI device when desktop is on VGA device: omxplayer --display 5 test.mp4

Comparison to Other RPi VGA Interfaces

This product has been designed for reliable long-term use, for example in a desktop computing environment, and as such offers proper protection to the Raspberry Pi to which it is attached given it's exposed hot-pluggable connector.

The product has been tested to:

  • Conducted Emissions - EN 55032:2015
  • Radiated Emissions - EN 55032:2015 (this product also meets FCC Part 15 Class B limits)
  • Electrostatic Discharge - BS EN 61000-4-2 : 2009 LEVEL 4

This product provides an interference free image with the use of the RPi wireless technologies (WiFi and Bluetooth) and implements control signal TTL buffers, since the Raspberry Pi GPIOs are not able to meet VGA specifications and may be over-driven by other designs.

Bill of Materials

Part Device Qty Mouser
C1,C2,C3 Do Not Populate 0
C4,C5 CC0603KRX7R8BB105 2 603-CC603KRX7R8BB105
C6,C7 CC0603KRX7R8BB224 2 603-CC603KRX7R8BB224
IC1 CM2009-00QR 1 748-CM2009-00QR
P1 M20-7832046 1 855-M20-7832046
R1, R10, R19 RC0603FR-07549RL 3 603-RC0603FR-07549RL
R2, R11, R20 RC0603FR-071K1L 3 603-RC0603FR-071K1L
R3, R12, R21 RC0603FR-072K2L 3 603-RC0603FR-072K2L
R4, R13, R22 RC0603FR-074K42L 3 603-RC0603FR-074K42L
R5, R14, R23 RC0603FR-078K66L 3 603-RC0603FR-078K66L
R6, R15, R24 RC0603FR-0717k4L 3 603-RC0603FR-0717K4L
R7, R17, R26 RC0603FR-0734K8L 3 603-RC0603FR-0734K8L
R8, R18, R27 RC0603FR-0769K8L 3 603-RC0603FR-0769K8L
X1 1-1734530-1 1 571-1-1734530-1

See Also