Didj and Leapster Explorer TV Out

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DidjTVOutPlasma.JPG

Introduction

This how-to outlines the basic steps to enabling your Didj or Leapster Explorer to send a composite video signal to your television. For the story behind how we got this working see rosincore.com


Requirements

A Didj or Leapster Explorer you are willing to disassemble and solder parts to.

Kernel compilation environment. For example:

Buildcross Didj Build Environment

Scratchbox Didj Kernel Build Environment


DJHI or similar mechanism to perform a UART boot or SD Card boot.

Breadboard

75 Ohm resistor

220pF capacitor (may be optional. this has been known to work with just the 75 Ohm resistor)

Composite jacks and or plugs

Didj Hardware Setup

The LF1000 processor contains a current-driven digital-to-analog converter that can drive an external screen via CVBS (composite video).

On the Didj, the DAC connection is exposed via Test Pad 6 (TP6) which can be found on the CPU side of the board.


Bga-closeup.jpg


To access TP6, you will need to remove the Didj main-board from the case. You may also find it more comfortable to work on TP6 with the LCD panel ribbon cable disconnected (its delicate, so be gentle as you release the ribbon cable)


Didj Mainboard Front.jpg


Solder a strand of Kynar, or an IDE strand, or similar small-gauge wire to TP6. (Make sure the wire is long enough to exit the case where desired.)


SolderingToTP6.jpg


Solder another strand of wire to ground. (ex: The metal on the cartridge socket is grounded.) (Make sure the wire is long enough to exit the case where desired)


Solder the end of the wire connected to TP6 to the middle pin of an RCA plug


Solder the end of the wire connected to GND to the outer ring of the RCA plug


Reassemble your Didj, routing the additional wires appropriately.


Leapster Explorer Hardware Setup

The LF1000 processor contains a current-driven digital-to-analog converter that can drive an external screen via CVBS (composite video).

On the Leapster Explorer, the DAC connection is exposed via Test Pad 30-Right (the pad to the right of the label marked TP30) which can be found on the CPU side of the board.


LX-TVout-Trace.jpg

To access TP30, you will need to remove the LX main-board from the case. You may also find it more comfortable to work on TP30 with the LCD panel ribbon cable disconnected (its delicate, so be gentle as you release the ribbon cable)


Leapster Explorer-Mainboard-front.jpg


Solder a strand of Kynar, or an IDE strand, or similar small-gauge wire to TP30R. (Make sure the wire is long enough to exit the case where desired.)


Solder another strand of wire to ground. (ex: The metal on the cartridge socket is grounded.) (Make sure the wire is long enough to exit the case where desired)


Solder the end of the wire connected to TP30 to the middle pin of an RCA plug


Solder the end of the wire connected to GND to the outer ring of the RCA plug


Reassemble your LX, routing the additional wires appropriately.


Filter Circuit

Build the filter circuit as follows:

(Note the capacitor may be optional. This hack has been known to work with just the 75 Ohm resistor)

DidjTVOutSchematic.png


Connecting

Connect the side of the circuit with the resistor to the Didj or LX, and the other side to your TV's Composite input jack.

Didj Software Setup

The LF Kernel sources already contains all the code necessary to enable you to connect your Didj to a TV via a Composite Video (RCA-style) connection.


To enable this capability, you must first have a kernel cross compilation environment set up (see Requirements).


The adjustment itself is simple. If you have just set up your kernel compilation environment and are compiling for the first time, set up your kernel by running make menuconfig. This generates a file called .config .


Edit .config and toggle (or if its not present, add) the CONFIG_LF1000_DPC_DUAL_DISPLAY directive as follows:


CONFIG_LF1000_DPC_DUAL_DISPLAY=y


Make any other adjustments you want and then build your kernel.

Take the resulting zImage and load it onto the Didj using Uart boot (or if toy have LB1.4 set up, an SD card)


Thats it! Shortly after rebooting, you should see an image on both the LCD and your TV.

(Note: This has been tested with a NTSC television. It is likely that some driver reconfiguration may be necessary to enable PAL.)

Leapster Explorer Software Setup

The Software setup for LX is a bit more involved. The code that activates tv-out seems to be toggled based on a GPIO, so it may not be as simple as setting a compile flag as mentioned above. Instead, the fbdev driver mentioned here is set up to support TV-out mode using the same configuration directive as is used for Didj.

Edit .config and toggle (or if its not present, add) the CONFIG_LF1000_DPC_DUAL_DISPLAY directive as follows:

CONFIG_LF1000_DPC_DUAL_DISPLAY=y

Make any other adjustments you want and then build your kernel. Take the resulting zImage, make a cbf file, and load it onto the LX using USB boot.

Thats it! Shortly after rebooting, you should see an image on both the LCD and your TV.

(Note: This has been tested with a NTSC television. It is likely that some driver reconfiguration may be necessary to enable PAL.)

To-dos

Add user-space dual-screen support.

Add user-space external screen control.