GP2X Scart Output Mod - Incomplete


clyder14

Still Fresh
Joined
Mar 6, 2009
Messages
4
Hi my abandoned attempt of SCART output from the GP2X's video encoder chip Conexant CX25874.
Got stuck on coding the CX25874 output mode using I2C and Rlyeh's minimal lib.

From the EXT port already runs the scart GREEN(svideo luminance) and scart BLUE(svideo chroma),
so I found and ran the scart RED and CVBS(?timing/blanking) to lifted EXT port pins - 11 & 12 (unused)

I have mistakenly run the CVBS through an LPF; only the RED signal requires the LPF !! doh.

I ran the RED and CVBS to an external PCB with two low pass filters(LPF).
The GP2X already has LPF's for the luminance and chroma.

I was close. If to take this up again with someones' help
with the coding side I will place a new PCB inside the case with the one LPF required.
(?for signal synchronisation)
 
JPEG Bay gallery
http://jpegbay.com/gallery/003632978-.html#1

CX-PIN__DAC__SCART COLOUR__SVIDEO__EXT PIN__SCART PIN
60--------DACA---RED--------------------------11---------15
61--------DACB---GREEN-------------V_Y------5----------11
62--------DACC---BLUE---------------V_C------4----------7
59--------DACD---CVBS------------------------12---------20


my board
A=dacc, B=dacb, C=daca ,D=dacd

The 'Open2X mmsp2_cx25874.c' contains code to set registers of the encoder chip using the I2C protocol.
e.g. gp2x_cx25784_write(0x7e, 0x54);

Part List:
SMD

Resistors
4 x 75ohm, 1% [0603 package]

Capacitors
4 x 22pF, 5% [0603 package]
4 x 270pF, 5% [0603 package]
4 x 330pF, 5% [0603 package]

Diodes
4 x Schottky BAT54S / DA204K [SOT23-N package]

Inductors
4 x 1.8uH, 5% [IND1210]
 
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