OSD Click

How does it work?

OSD Click is based on the MAX7456, a single-channel monochrome on-screen display generator from Analog Devices. This Click board™ accepts composite NTSC or PAL signals and inserts a user-defined OSD as a layer over the video. The MAX7456 includes an input clamp, sync separator, video timing generator, OSD insertion MUX, nonvolatile character memory, display memory, OSD generator, and more. As the user-defined 256 (12 x 18 pixel) character set comes preloaded, combined with a video stream, the Click board™ generates a CVBS signal. The operating mode depends on the number of displayed rows, whereas for NTSC, it is 13 rows x 30 chars, and for PAL, it is 16 rows x 30 chars.

This Click board™ communicates with the host MCU through a standard SPI serial interface of the mikroBUS™ socket. The MAX7456 provides vertical, horizontal, and loss of sync signals for system synchronizations. These synchronizations are essential for the OSD layer to stay in place. The vertical synchronization feature is accessed through a VS line routed to the INT of the mikroBUS™ socket, while the horizontal sync is accessed through the HS line routed to the PWM pin of the mikroBUS™ socket. Loss of synchronization signal, marked as LOS and routed to the mikroBUS™ AN pin, will go to a low logic state when 32 consecutive, valid sync pulses are received, otherwise will go high. OSD Click also possesses a general reset feature accessed with the RST pin of the mikroBUS™ socket.

This Click board™ also has two RCA connectors labeled IN and OUT for connecting input and output video signals. Coupling capacitors are also populated on the video connection lines for guaranteed specified line time (LTD) and video clamp setting time.

This Click board™ can be operated only with a 5V logic voltage level. The board must perform appropriate logic voltage level conversion before using MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.

Specifications

Pinout diagram

This table shows how the pinout on OSD Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
Loss of Signal	LOS	1	AN	PWM	16	HS	Horizontal Synchronization
Reset	RST	2	RST	INT	15	VS	Vertical Synchronization
SPI Chip Select	CS	3	CS	RX	14	NC
SPI Clock	SCK	4	SCK	TX	13	NC
SPI Data OUT	SDO	5	MISO	SCL	12	NC
SPI Data IN	SDI	6	MOSI	SDA	11	NC
	NC	7	3.3V	5V	10	5V	Power Supply
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

OSD Click electrical specifications

Software Support

We provide a library for the OSD Click as well as a demo application (example), developed using MIKROE compilers. The demo can run on all the main MIKROE development boards.

Package can be downloaded/installed directly from NECTO Studio Package Manager (recommended), downloaded from our LibStock™ or found on MIKROE github account.

Library Description

This library contains API for OSD Click driver.

Key functions

• osd_clear_display_memory This function clears display memory.

• osd_insert_custom_char This function writes custom character.

• osd_enable_video_buffer This function enables video buffer.

Example Description

This demo performs basic OSD Click functionality - write text on screen.

 void application_task ( void ) 
 { 
     log_printf( &logger, "rn Writing characters on the screen...rn" ); 
     for ( uint8_t cnt = 0; cnt < 30; cnt++ ) 
     { 
         if ( HEADER_TEXT[ cnt ] != ' ' ) 
         { 
             osd_write_character( &osd, 1, cnt, HEADER_TEXT[ cnt ] ); 
         } 

         if ( MESSAGE_TEXT[ cnt ] != ' ' ) 
         { 
             osd_write_character( &osd, 7, cnt, MESSAGE_TEXT[ cnt ] ); 
         } 

         if ( FOOTER_TEXT[ cnt ] != ' ' ) 
         { 
             osd_write_character( &osd, 14, cnt, FOOTER_TEXT[ cnt ] ); 
         } 

         Delay_ms ( 1000 ); 
     } 

     log_printf( &logger, " Clear displayrn" ); 
     osd_clears_char_places( &osd, 0, 0, 16, 30 ); 
     Delay_ms ( 1000 );
     Delay_ms ( 1000 );
     Delay_ms ( 1000 ); 
 }

The full application code, and ready to use projects can be installed directly from NECTO Studio Package Manager (recommended), downloaded from our LibStock™ or found on MIKROE github account.

Other MIKROE Libraries used in the example:

• MikroSDK.Board
• MikroSDK.Log
• Click.OSD

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 Click or RS232 Click to connect to your PC, for development systems with no UART to USB interface available on the board. UART terminal is available in all MIKROE compilers.

mikroSDK

This Click board™ is supported with mikroSDK - MIKROE Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.