Our blog

March 28, 2016   Posted by: Dr. Ace Jeangle

Some updates, what kept us busy

Hello, everyone!

We kept silent for many months, and we had reason for this – we were working hard on new products and will present them soon in our web store:

  1. First of all, we are going to offer cheap LCD solution for cheap C.H.I.P. board. We decided that $9 board deserves $19 LCD, and now preparing mass production of 4.3″ LCD with resistive touchscreen that can be directly connected to connector U13 on board with single cable. You will get high-brightness 480×272 screen with integrated touch and backlight control.
    4.3" LCD for C.H.I.P. board
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  3. Next news will be interesting for all new Van Goghs and Rembrandts who are in digital arts or just want to draw his cat’s portrait on PC. I’m talking about digitizer with pressure-sensitive stylus. Currently, there are several companies who offer such kind digitizers. The most famous is Wacom, plus several less known companies like Huion, VisTablet etc. Of course, Wacom is the best, but their prices are crazy. You have to sell your kidney to buy their digitizer. We are going to offer 10″ digitizer with gorgeous FullHD (1920×1080) screen based on Wacom technology that you can simply connect to your PC/notebook with HDMI+USB. Then you simply buy Wacom stylus and start your career in digital art. Price will be around $130.
    10" digitizer with FullHD LCD
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  5. We finished development of new hardware platform called Gen2, it includes 3 HDMI boards with different LCD interfaces: LVDS, MIPI and eDP. All are compact, have convenient pin-type header for LCD cable, interface protection chips, HDMI audio decode, all required on-board voltage generators (like VSP/VSN for MIPI panels) and backlight control with 1024 steps. Boards will be available for purchase in April with cost $34.95 each. We will also offer medium size (5″-7″) FullHD LCD panels for MIPI board.
    Gen2 board (HDMI-LVDS)
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  7. Finally, we will offer new versions of our popular black-frame and open-frame 7″ LCD panels based on Gen2 board. The price will be the same, but you will get more robust solution with long-term support.
    7" LCD with Gen2 board

 

Follow us on Twitter @ChalkElec to get instant updates.

 

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February 5, 2015   Posted by: Dr. Ace Jeangle

How to use FullHD+ LCD

Our 10″ FullHD+ LCD bundle supports 24-bits color and has WUXGA (1920×1200 px) resolution. Take note that your host board should support 1920×1200 resolution, otherwise you will get no video output.
Bundle consists of LCD panel, HDMI converter board, and LVDS cable to connect converter to LCD panel. You can also buy optional cables (miniHDMI and miniUSB), power supply to power converter and LCD, ambient light sensor for automatic brightness control, and LCD holder: 10″ FullHD+ LCD with HDMI interface

HDMI-dualLVDS converter board has the following connectors:
FullHD+

Connecting LCD

You should use included LVDS cable to connect LCD to HDMI converter board. Please, take care to correctly insert LCD side of cable – contacts should be on top. Use your nails or tweezers to insert cable completely into LCD connector.
LVDS cable, LCD side

Optional ambient light sensor should be connected with red wire into pin 1 on board connector:
Ambient light sensor

Logic and backlight voltages for LCD are generated on board and supplied by the same LVDS cable, so you don’t need separate power supply for LCD or backlight voltage generator.

Powering LCD

LCD with converter board take up to 1.2A/5A when backlight is set to maximum value. Board and LCD can be powered either by external power supply (5V at least 2A, jack is OD=2.6mm, ID=0.65mm, positive central pin) or by USB. By default it can be powered by external supply only. For USB power you should install 0R resistor in R12 position. Check that your USB host can provide enough current. CAUTION! Do not connect external power supply when R12 is installed, it can damage your USB port.

Basic LCD functionality

We ship LCD with simple demo firmware that turns on LCD backlight and video processor when input video signal is detected. If video signal is lost, LCD backlight will be turned off. On-board LED shows status of video signal – LED is on when active video signal is detected. You can always check that hardware is working well by connecting LCD with this basic firmware into standard PC running Windows. For advanced functionality you will need to update firmware as described below.

Firmware update with USB bootloader

We constantly release new firmware for our products to extend functionality and fix possible bugs. Converter board has embedded USB bootloader for easy firmware update. To update firmware you should switch converter board to bootloader mode by shorting both pins on ambient light sensor connector with jumper, then turn on power. Green LED will light on, and you will have 3 seconds to remove jumper in order to start bootloader. Green LED will blink when bootloader is active. You should follow steps 4 and 5 of this firmware upload procedure: Firmware upload.
HID USB bootloader program for PC is available here: HID USB bootloader.
Latest version of firmware is always available here: FullHD+ firmware

Ambient light sensor and backlight brightness

Ambient light sensor is available as an option, and can measure ambient light level for automatic brightness control.
ambient light sensor
Ambient light sensor should be connected to connector J1, red color wire to pin 1 on connector. You will need latest firmware in order to get automatic backlight control. Also, with last firmware you can control backlight from your host board or PC through USB HID commands: How to control LCD backlight (USB HID)

  • Maximum brightness (MAX_BL parameter) is 35 for this 10″ LCD
  • Report ID for backlight control is 0

Converter board schematic

Board schematic is available here: http://goo.gl/NSWTIQ

Technical drawing of LCD

Technical drawing of LCD is available here: FullHD+ LCD drawing

See in action

Video with dualLVDS converter board and our FullHD+ LCD is available here: FullHD+ LCD with HDMI dualLVDS converter

Follow us on Twitter to get instant notification about new firmware release:

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February 4, 2015   Posted by: Dr. Ace Jeangle

How to control LCD backlight (USB HID)

Starting from version 2.0 all firmwares for our LCD and HDMI converters support LCD backlight control through standard USB HID protocol.

HID report descriptor

The following HID report descriptor is used:

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    0x05, 0x0C,             //    Usage Page (Consumer)
    0x09, 0x01,             //    Usage (Consumer Control)
    0xA1, 0x01,             //    Collection (Application)
    0x15, 0x00,             //       Logical Minimum (0)
    0x25, 0x01,             //       Logical Maximum (1)
    0x75, 0x01,             //       Report Size (1)
    0x95, 0x07,             //       Report Count (7)
    0x19, 0x6F,             //       Usage Minimim (0x6F)
    0x29, 0x75,             //       Usage Maximum (0x75)    
    0x91, 0x02,             //       * Output (Data, Var, Abs)
    0x95, 0x01,             //       Report Count (1)
    0x91, 0x03,             //       * Output (Const, Var, Abs)
    0x25, 0x23,             //       Logical Maximum (35)
    0x75, 0x08,             //       Report Size (8)
    0x09, 0x71,             //       Usage (0x71 -  Display Brightness)
    0x91, 0x02,             //       * Output (Data, Var, Abs)
    0x09, 0x35,             //       Usage (0x35 - Illumination)
    0x26, 0xFF, 0x00,       //       Logical Maximum (255)
    0x81, 0x02,             //       ** Input (Data, Var, Abs)
    0x05, 0x20,             //       Usage Page (Sensors)
    0x09, 0x41,             //       Usage (0x41 -  Ambient Light Sensor)
    0x81, 0x02,             //       ** Input (Data, Var, Abs)
    0xC0                    //    End Collection

Report usages follow recent changes in official USB HID specification proposed by Microsoft in change request #HUTRR41. Interface # is 0 for HDMI-dualLVDS converter and FullHD+ LCD bundle, Interface # is 1 for open frame/black frame 7″ LCD and for new 10″ integrated LCD. Report ID is 0 for all cases.

Packet format

Firmware accepts 2-bytes packet request from host and reply with 2-bytes packet with information about current backlight mode and ambient light level:
Backlight HID format

Only one bit can be active in command byte of request packet. If bit 5 is active (Set Brightness command), then next byte contains desired brightness level. For others commands second byte is ignored. LCD will reply with current backlight status and ambient light sensor value to any received command. To get current status without performing command you can send request with command byte equal to 0. MAX_BL is 35 for HDMI-dualLVDS converter and FullHD+ LCD bundle, MAX_BL is 18 for open frame/black frame 7″ LCD and for new 10″ integrated LCD.

How to send commands

The simplest way to communicate with HID devices is to to use cross-platform library HIDAPI from Signal11. With HIDAPI it is just several lines of code to control LCD brightness:

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#include <stdio.h>
#include "hidapi.h"

// Try to open HID device and return pointer to opened device
hid_device* openHID() {
    struct hid_device_info *devs, *cur_dev;
    hid_device* device = NULL;
    int iface = 1;  // We use interface# 1 for 7" and 10", and interface# 0 for dualLVDS/FullHD+

    // VID=0x04D8, PID=0xF724 for 7" and 10" multi-touch firmware, interface# is 1
    // VID=0x04D8, PID=0xF723 for 7" and 10" single-touch firmware, interface# is 1
    // VID=0x04D8, PID=0x003F for dualLVDS/FullHD+, interface# is 1
    devs = hid_enumerate(0x04D8, 0xF724);
    if (devs == NULL) {
        devs = hid_enumerate(0x04D8, 0xF723);
        if (devs == NULL) {
            devs = hid_enumerate(0x04D8, 0x003F);
            if (devs == NULL) return NULL;
            else iface = 0;
        }
    }

    // Walk through all enumerated devices to find one with correct interface number
    cur_dev = devs;
    while (cur_dev) {
        if ((cur_dev->interface_number) == iface) {
            device = hid_open_path(cur_dev->path);
            printf("Found Backlight interface at path: %s", cur_dev->path);
            break;
        }
        cur_dev = cur_dev->next;
    }
    hid_free_enumeration(devs);

    return device;
}

int main(int argc, char *argv[]) {
    hid_device* device=NULL;
    unsigned char buf[3];

    buf[0] = 0x0;   // Report ID (0)
    buf[1] = 0x04;  // Command (0x20 - Set Backlight)
    buf[2] = 9;     // Backlight value for command Set Backlight

    hid_init();

    device = openHID();
    if (device == NULL) {
        puts("Can't find USB device with interface for backlight");
        return -1;
    }

    hid_set_nonblocking(device, true);


    printf("Writing bytes: %02X,%02X,%02X\n", buf[0], buf[1], buf[2]);

    if (hid_write(device, buf, 3) == -1) {
        puts("Error writing bytes to device!");
        hid_close(device);
        return -1;
    }

    if (hid_read_timeout(device, buf, 2, 100) == -1) {
        puts("Error reading bytes to device!");
        hid_close(device);
        return -1;
    }

    printf("Received bytes: %02X,%02X\n", buf[0], buf[1]);

    return 0;
}

Above example is universal and will work with all our products with USB backlight control feature.

GUI application for LCD control

Cross-platform GUI application to control different LCD settings including brightness is available here:
LCD control GUI
You will need Qt framework to build it from sources.

See in action

Video with backlight test using our dualLVDS converter FullHD+ LCD is available here: Backlight test video

Follow us on Twitter to get instant notification about updates: h

3 comments posted in: blog   |   How-To
January 30, 2015   Posted by: Dr. Ace Jeangle

How to use HDMI-dualLVDS converter

Our dualLVDS converter has two LVDS channels and supports 24-bits color panels with up to WUXGA (1920×1200 px) resolution. It also has on-board configurable backlight voltage generator and microcontroller with USB interface. We offer this converter as a standalone product, and also in bundle with 10″ WUXGA panel.

DualLVDS converter board has the following connectors:
HDMI-dualLVDS converter

Powering board

Converter board alone takes up to 0.4A current in active mode, with connected 10″ FullHD+ current goes up to 1.2A when backlight is set to maximum value. Board and LCD can be powered either by external power supply (5V at least 2A, jack is OD=2.6mm, ID=0.65mm, positive central pin) or by USB. By default it can be powered by external supply only. For USB power you should install 0R resistor in R12 position. CAUTION! Do not connect external power supply when R12 is installed, it can damage your USB port.

Backlight voltage generator

Converter has on-board configurable backlight voltage generator that can deliver up to 35V/1A. Backlight voltage can be set with R3, R11 resistors (see above picture for formula). We supply boards with default 24V backlight voltage. Take note that R11 should be in 5K – 20K range. If LCD backlight takes more than 3W, then U6 and L1 inductor can have temperature up to 100C degree. In this case you should use additional heat sink to avoid overheating.

LVDS cable

If you buy standalone board, then you will need to make your own LVDS cable for your LCD panel. We supply mate housing connector and 50 pcs of pin terminals together with board, they can be crimped to cable wires with AWG #32 crimp tool. We recommend using PA-09 crimp pliers, it has affordable price and provides high quality results. Below is pinout of LVDS connector, PDF version is available here: dualLVDS board pinout.
dualLVDS Pinout
Pins GPIO_xxx are connected directly to PIC microcontroller and can be used to control different functions of LCD. We ship board with our standard example program (see source code below) that uses pin GPIO_RA5 to turn on LCD backlight when input video signal is detected. If video signal is lost, LCD backlight will be turned off. Also, pin GPIO_RC5 is connected to PIC PWM generator, and can be used to control brightness of LCD backlight.

Update of EDID information

We supply our converter board with pre-loaded EDID data for our 10″ FullHD+ LCD (resolution 1920×1200 px). You will need to update EDID information in converter in order to use it with your own LCD. EDID update procedure is described here: How to program custom EDID data in HDMI converter

Firmware update with USB bootloader

Board is supplied with embedded USB bootloader for easy firmware upload. To update firmware you should start board in bootloader mode by shorting both pins on ambient light sensor connector with jumper, then turn on power. Green LED will light on, and you will have 3 seconds to remove jumper in order to start bootloader. Green LED will blink when bootloader is active. You should follow steps 4 and 5 of this firmware upload procedure: Firmware upload HID USB bootloader is available here: HID USB bootloader. You can use firmware for our FullHD+ LCD bundle for your own LCD projects, latest version of firmware is available here: dualLVDS/FullHD+ firmware

Building PIC firmware

To build own PIC firmware you will need MPLAB.X environment from Microchip with XC8 compiler: MPLAB X, XC8 compiler.
Bootloader occupies the program memory region 0x000-0x903. The application firmware is supposed to occupy the 0x904-[end of flash] region of program memory.
Here are two linker setting changes that are required for the application project:

  1. Under the build configuration–>XC8 global options–>XC8 linker–>Option categories:Additional options the “Codeoffset” must be set to: 0x904
  2. Under the build configuration–>XC8 global options–>XC8 linker–>Option categories:Memory model, the “ROM ranges” must be set to: default,-0-903

In addition to the above, make certain that all configuration bit settings between the bootloader firmware project, and the application firmware project, match 100% exactly, see our example firmware for details:

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#include "typedefs.h"

__CONFIG(FOSC_INTOSC & WDTE_OFF & PWRTE_ON & MCLRE_OFF & CP_OFF & BOREN_ON & CLKOUTEN_OFF & IESO_OFF & FCMEN_OFF);
__CONFIG(WRT_OFF & CPUDIV_NOCLKDIV & USBLSCLK_48MHz & PLLMULT_3x & PLLEN_ENABLED & STVREN_ON &  BORV_LO & LPBOR_OFF & LVP_OFF);

#define _XTAL_FREQ 48000000                     // Frequency of crystal (INTOSC in our case)

void main(void) {
    OSCCON = 0xFC;                              // 3x PLL enabled from 16MHz HFINTOSC
    ACTCON = 0x90;                              // Enable active clock tuning from USB
    while(OSCSTATbits.PLLRDY == 0);             // Wait for PLL ready/locked

    ANSELAbits.ANSA4=0; TRISAbits.TRISA4=1;     // Define SCDT In pin (input)
    LATAbits.LATA5=0; TRISAbits.TRISA5=0;       // Define SCDT Out pin (output, default to 0)
    LATCbits.LATC5=0; TRISCbits.TRISC5=0;       // Define PWM pin (output, default to 0)
    LATCbits.LATC3=1; TRISCbits.TRISC3=0;       // Define LED pin (output, default to 1 - LED Off)

    while(1) {
        // If video signal is detected
        if (PORTAbits.RA4) {                    
            LATAbits.LATA5=1;                   // Enable video outputs
            LATCbits.LATC5=1;                   // Enable backlight (PWM=1 - max. brightness)
            LATCbits.LATC3=0;                   // Turn LED On
        }
        // If video signal is lost
        else {
            LATAbits.LATA5=0;                   // Disable video outputs
            LATCbits.LATC5=0;                   // Disable backlight (PWM=0 - turn off backlight)
            LATCbits.LATC3=1;                   // Turn LED Off
        }
    }
}

Ambient light sensor and backlight brightness

Ambient light sensor is available as an option, and can measure ambient light level for automatic backlight control.
ambient light sensor
Ambient light sensor should be connected to connector J1, red color wire to pin 1 on connector. Light level is available as a voltage in range 0 (dark) to 2.5V (max. light) on pin RC2 (ADC channel 6) of PIC microcontroller. Backlight brightness can be controlled with help of PWM signal on GPIO_RC5. Additional information about backlight control through USB HID commands is available in this how-to: How to control LCD backlight (USB HID)

Board schematic

Board schematic is available here: http://goo.gl/NSWTIQ

See in action

Video with dualLVDS converter board and our FullHD+ LCD is available here: FullHD+ LCD with HDMI dualLVDS converter

Follow us on Twitter to get instant notification about new firmware release:

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