ESP32 Forum

Posted: **Tue Dec 14, 2021 5:54 pm**

Hi,

As there is still no documentation on the LCD_CAM peripheral, i would like espressif help me with this peripheral.

Below are the codes that apparently are working and the code that is not working.
Can i only send data with the data/command pin = 1 through gdma ?

Code apparently it's working to send a command:
* Clock io pin = OK
* data/command io pin = 0 (ok).
* chip select io pin = always 0.
* data 0.....7 io pins = ok.

Code: Select all

inline void hw_lcd_write_command( uint32_t command )      
{
    LCD_CAM.lcd_user.lcd_cmd = 1;   // R/W; bitpos: [26]; default: 0. 1: Be able to send command in LCD sequence when LCD starts. 0: Disable.  
    LCD_CAM.lcd_user.lcd_dout = 0;  // R/W; bitpos: [24]; default: 0. 1: Be able to send data out in LCD sequence when LCD starts. 0: Disable.      
    
    LCD_CAM.lcd_cmd_val.lcd_cmd_value = command;  // lcd_cmd_value : R/W; bitpos: [31:0]; default: 0. The LCD write command value. 
        
    LCD_CAM.lcd_user.lcd_update = 1;  // R/W; bitpos: [20]; default: 0. 1: Update LCD registers, will be cleared by hardware. 0 : Not care. Update parameters before start transaction.
    LCD_CAM.lcd_user.lcd_start = 1;   // R/W; bitpos: [27]; default: 0. LCD start sending data enable signal, valid in high level.
}

Code not working to send a parameter with data/command pin = 1 without gdma.
* Clock io pin = OK i think ( "2 clock cycles with LCD_CAM.lcd_user.lcd_always_out_en = 0" , and 1 clock cycle with LCD_CAM.lcd_user.lcd_always_out_en = 1" ).
* data/command io pin = 1 (ok).
* chip select io pin = always 0.
* data 0.....7 io pins = NOT OK, no output data.

Code: Select all

inline void hw_lcd_write_data( uint32_t data )      
{
    LCD_CAM.lcd_user.lcd_cmd = 0;   // R/W; bitpos: [26]; default: 0. 1: Be able to send command in LCD sequence when LCD starts. 0: Disable.  
    LCD_CAM.lcd_user.lcd_dout = 1;  // R/W; bitpos: [24]; default: 0. 1: Be able to send data out in LCD sequence when LCD starts. 0: Disable.
            
    LCD_CAM.lcd_cmd_val.lcd_cmd_value = data;  // R/W; bitpos: [31:0]; default: 0. The LCD write command value. 
      
    LCD_CAM.lcd_user.lcd_update = 1;  // R/W; bitpos: [20]; default: 0. 1: Update LCD registers, will be cleared by hardware. 0 : Not care. Update parameters before start transaction.
    LCD_CAM.lcd_user.lcd_start = 1;   // R/W; bitpos: [27]; default: 0. LCD start sending data enable signal, valid in high level.
}

Thank's for the help.

Posted: **Wed Dec 15, 2021 9:01 pm**

Hi,

750 nanoseconds to start send a command to LCD_CAM io.

2,7 microseconds to service LCD_CAM interrupt.

Is that correct ?

How can i decrease the interrupt latency in LCD_CAM interrupt ?

Thank's.

Posted: **Thu Dec 16, 2021 2:49 am**

That sounds about right, honestly. Interrupts on the ESP32/Xtensa aren't that fast I'm afraid.

Posted: **Thu Dec 16, 2021 6:55 pm**

Baldhead wrote: ↑
Tue Dec 14, 2021 5:54 pm
Code not working to send a parameter with data/command pin = 1 without gdma.
* Clock io pin = OK i think ( "2 clock cycles with LCD_CAM.lcd_user.lcd_always_out_en = 0" , and 1 clock cycle with LCD_CAM.lcd_user.lcd_always_out_en = 1" ).
* data/command io pin = 1 (ok).
* chip select io pin = always 0.
* data 0.....7 io pins = NOT OK, no output data.
Code: Select all
inline void hw_lcd_write_data( uint32_t data )      
{
    LCD_CAM.lcd_user.lcd_cmd = 0;   // R/W; bitpos: [26]; default: 0. 1: Be able to send command in LCD sequence when LCD starts. 0: Disable.  
    LCD_CAM.lcd_user.lcd_dout = 1;  // R/W; bitpos: [24]; default: 0. 1: Be able to send data out in LCD sequence when LCD starts. 0: Disable.
            
    LCD_CAM.lcd_cmd_val.lcd_cmd_value = data;  // R/W; bitpos: [31:0]; default: 0. The LCD write command value. 
      
    LCD_CAM.lcd_user.lcd_update = 1;  // R/W; bitpos: [20]; default: 0. 1: Update LCD registers, will be cleared by hardware. 0 : Not care. Update parameters before start transaction.
    LCD_CAM.lcd_user.lcd_start = 1;   // R/W; bitpos: [27]; default: 0. LCD start sending data enable signal, valid in high level.
}

@ESP_Sprite,

Could you help me with this ?

Posted: **Thu Dec 16, 2021 7:05 pm**

Hi @ESP_Sprite,

A strange thing happens in this code below.

I am monitoring, with a oscilloscope, the clock and data pin bit 1.

The data pin bit 1 should be alternating infinitely, but sometimes, the pin print two consecutive 0 or sometimes two consecutive 1.
The problem occurs randomly, sometimes the pin alternates 11 times, sometimes 48 times, sometimes another value, until the problem appears.

What can be wrong ?

Thank's.

Code: Select all

void app_main(void)
{  
    hw_lcd_init();
    
    while(1)
    {
        hw_lcd_write_command( 0xAA );
        vTaskDelay( pdMS_TO_TICKS(500) );

        hw_lcd_write_command( 0x55 );
        vTaskDelay( pdMS_TO_TICKS(500) );    
    }
}


inline void hw_lcd_write_command( uint32_t command )      
{
    hw_lcd_clear_transfer_end_interrupt_status();  // LCD_CAM.lc_dma_int_clr.lcd_trans_done_int_clr = 1;   interrupt disabled.    

    LCD_CAM.lcd_user.lcd_cmd = 1;   // R/W; bitpos: [26]; default: 0. 1: Be able to send command in LCD sequence when LCD starts. 0: Disable.  
    LCD_CAM.lcd_user.lcd_dout = 0;  // R/W; bitpos: [24]; default: 0. 1: Be able to send data out in LCD sequence when LCD starts. 0: Disable.        
    
    LCD_CAM.lcd_cmd_val.lcd_cmd_value = command;  // lcd_cmd_value : R/W; bitpos: [31:0]; default: 0. The LCD write command value. 
        
    LCD_CAM.lcd_user.lcd_update = 1;  // R/W; bitpos: [20]; default: 0. 1: Update LCD registers, will be cleared by hardware. 0 : Not care. Update parameters before start transaction.
    LCD_CAM.lcd_user.lcd_start = 1;   // R/W; bitpos: [27]; default: 0. LCD start sending data enable signal, valid in high level.
   
    while( hw_lcd_transfer_done_status() );  // !LCD_CAM.lc_dma_int_raw.lcd_trans_done_int_raw;  interrupt disabled. polling flag.
}

Posted: **Sun Jun 05, 2022 8:03 pm**

In the file "espressif/esp32-camera/target/esp32s3/ll_cam.c" can anyone explain how the registers in "soc/lcd_cam_reg.h" are actually accessed? The register header is included but I don't see anywhere it's used. I do see in another header file "soc/lcd_cam_struct.h" where register structures are created but I don't see how they connect to the actual register definitions.

In short I'm trying to figure out how the low level registers are actually accessed by the given example code.

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