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Generate LED pulse trains with LED171596A

Other Parts Discussed in Thread: LED171596A, LP5036

Hi there, I wonder this chip or its EVM has the capability to generate LED pulse trains? I know it can drive up to 96 Leds with constant current, but in my applications I would like to use a TTL to control the lighting of the LEDs, which I don't find doable in the GUI software. Could you let me know if it is possible? Or which alternative chips should I use for realizing the continuous LED pulses for multiple channels?

Much appreciated.

 

  • Hi Yi,

    Do you mean that you need to change the output PWM duty cycle? Here is the brightness registers to set PWM value for all LEDs.

    Could you help to share your application background and requirement for LED driver?

  • Dear Hardy,

    I wanted to output ~50Hz laser pulse trains. Basically, I want the output to flash on/off around 20ms, However, I found the minimum frequency of PWM output is 100Hz. So I am asking how I can output PWM signals with even smaller frequency. I understand the PWM frequency is set high to make the light constant, but for my applications, I need the light to be on/off with certain frequency(below 100Hz). Is there any ways to manage it? From the MCU end or maybe after the driver output?  I am using the TM4C123G MCU launchpad and the LED171596A EVM to drive LED arrays.

    Let me know if I need to clarify anything further,

    Thanks! 

  • Hi Yi,

    Yes the minimum frequency of output PWM is 100Hz. If you need to achieve flash on/off, you need to use MCU writing 0/FFh commands to LEDxx_bri in 50Hz.

  • Thanks Hardy,

    May I ask if the launchpad board (TM4C123G) is able to do the writing or I have to switch to another board?  If yes, could you simply instruct how to? Just provide the basic idea would be great. I am not a hardware engineer so it is a bit hard for me to find how to do the 0/FFh writing you mentioned.

    Thanks a lot

    Yi

  • Hi Yi,

    I think TM4C123G should be OK since it only need basic I2C/SPI interface and Timer functions. Writing LEDxx_bri register to FFh can set LEDxx on while write it 0 make LEDxx off. So your MCU can sending these commands with 20ms duty to achieve your requirement.

  • Thanks again Hardy. I will look into it following your instruction. One last question, should I use the TM4C123G Tivaware to do this writing? Like using the Code composer studio? Really appreciate if you could elaborate a bit more.

    Yi

  • Hi Yi,

    You can use any IDE that can support TM4C123G. I think CCS is a good one to use. Sorry that I am the engineer for LED driver but not MCU. If you have any further question about the usage of TM4C123G, you could start another E2E thread to consult the experts. 

  • Many thanks, Hardy. Totally understood. I just had one more question for you after I tried to command the LED driver today. I used the GUI software to do it since it has a command function. However, when I set the LEDxxBri to be on and off, the time for this process can be more than 100 ms. Are you sure the duty can be down to 20 ms when using command lines to control it? Really appreciate if you could help me make sure the capability.

    Best,

    Yi

  • Hi Yi,

    I am not so clear about your process. How do you set the LEDxx_bri registers on and off?

  • Hi Hardy,

    Thanks for asking me this.

    I used the GUI software of the LED driver EVM board. I believe it is a reprogramed version of the software of MCU. There is a command line in this software, I wrote lines like "write(LEDxx_bri,0)" and "write(LEXxx_bri, 0xFFFF)". I saw the light started to flash with those commands but it can't be done with the frequency I want(like 50 Hz). I am wondering if I have to do it directly in MCU or what. Really appreciate your help!

    Best,

    Yi 

  • Hi Yi,

    Do you have a screen capture of the GUI you used? I do not think our official GUI have this 'command line' function. Maybe the GUI was developed by someone else. Anyway it should be OK to set a 20ms timer for TM4C123G.

    One more thing I am curious is that actually this device is not public anymore due to commercial reason. Is it used in some previous projects?

  • Hi Hardy,

    See below the GUI and command lines.

    I ordered this board before, like weeks ago,  at that time It is still available for ordering. Let me know if there is any questions regarding it.

    Best,

    Yi

  • Hi Yi,

    Well I find the console panel, which I never not used before... I think this device is still on sell in some selling agents but not public at TI.com anymore. Please feel free to let me know if there are any question about the operation of this device.

  • Dear Hardy,

    Thanks for the previous help and hope you had a good holiday. 

    I went back to this project these days and wanted to ask some more questions about the project if possible. 

    So I know there is a official GUI for the EVM, but it does not have the on/off function I need. I wonder if you could provide the source code of the GUI since it is basically reprogramming the Tivaware software. In that case, I could enable the controlling much easier. I also understand this might be too much to ask.

    Another question is that you mentioned this module is actually not supported by TI due to commercial reason. That's probably why the resources are limited. I wonder if TI have any alternatives after this that could provide high-channel-count LED drivers which are still supported? 

    Best,

    Yi

  • Hi Yi,

    Here is some materials you could refer. 

    tiva_led171596_demo_dimming.zip

    tiva_led171596_demo_effects.zip

    tiva_led171596A_ring_sample_code.zip

    How many LEDs you need to drive? We have LP5036 which is directly driving structure with 36 channel per unit. 3 pcs LP5036 could cover the channel number of one LED171596 and the cost is also lower. For similar matrix structure device, we have one developing device which would release in 2Q2021. If your design window could wait to that time, it is also a better choice. 

  • Thanks Hardy, those files are extremely helpful to me! Much appreciated. Are those files generated with Arduino?

    Thanks for introducing the new chip to me as well, I will definitely use some of them in the future.

    Best,

    Yi

  • Yes I suppose so.

  • Thanks, Hardy. Those files are helpful. But all of them are missing the header fIle SPI.h. I checked the driver library, the header file should be modified a lot in this project since I can't find all the APIs used in the codes. Is there any chance you could provide the modified SPI.h file?

    I know I am asking tons of questions. I am very new to those stuff and really appreciate your patience!

    Yi

  • Hi Yi,

    Sorry that I could not find the engineer who build this code. You may need to modify the codes and use the driver in your system.