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DLPC3470: DLPC3470 Opcode Questions

Geunghyul Lim
Prodigy 30 points
Part Number: DLPC3470

Hello, TI expert

 

I am making a program to directly control Dlpc3470 through STM32duino I2C communication.

While testing, I noticed something odd.
To set the LED Current to 300mA, 0x2C (LSByte) and 0x01 (MSB) were input as parameters of Write Opcode in order.
However it was set to about 738mA.


More test results..

Multiply the current value I want to set by about 0.405, I found out that I had to put the hexadecimal number corresponding to the multiplied value as a parameter.

That is, to set LED Current to 300mA, 0x79(LSByte), 0x00(MSByte) must be input as parameters.

You would like to know why you need to enter the converted value rather than 300 (DEC) hexadecimal. I would also like to know the formula used for the conversion.

Thanks for reading the question

  • 0
    TI__Genius 9971 points

    Hello Lim, 

    Welcome to TI E2E forums and thanks for showing interest in DLP technology. Can you please refer to the Software Programmer's guide, the format information for input parameter various commands would be available in it (https://www.ti.com/lit/pdf/dlpu075)

    Regards,

    Mayank

  • 0 in reply to Mayank Khandelwal
    Prodigy 30 points

    Thanks for your reply.

    But this didn't solve my question.

    I am using "DLP@Pico Display and Light Control EVM" software to adjust the brightness of the projector.

    When I set the output of the RGB LED to 500mA and checked the debug value of "DLP@Pico Display and Light Control EVM", it was confirmed that 0xCA(202) was used instead of 0x1F4(500).

    My question is "why does the converted value go into the parameter of 'Write RGB LED Current PWM(54h)' and not the actual input value?"

    The Dlpu075 datasheet provided by TI does not answer my question.

    Thanks for reading the question

  • +1 in reply to Geunghyul Lim
    TI__Genius 12595 points

    Hello User,

    The value that is seen in the Intellibright LED Current window provides an estimated current that will pass through the LED. The command that is sent to the DLPC (as seen in the Debug tab) will be the hexadecimal PWM value needed to output the current specified. The processing for this PWM value is done at the front-end so the PWM value is of more use to the DLPC than the targeted current output. Section 3.2.5 of the DLPC3470 Software Programmer's Guide can provide further information on the command that is being sent to the DLPC.

    As a test, you might consider measuring the current through the specified LED to ensure that 500mA is flowing.

    Regards,

    Austin

  • 0 in reply to Austin Snyder
    Prodigy 30 points

    Thank you for your reply.

    Now I know what I'm misunderstanding.

    Thank you for your kind explanation so that I can understand

    Regards,

    Lim