Difficulty with SPI with NHD-4.3-480272FT-CSXV-CTP

makoto.inoue

Hi All,
I've recently started working on a project that plans to use NHD-4.3-480272FT-CSXV-CTP, and am experiencing some challenges.
The issue seems similar to the one mentioned in topic: https://support.newhavendisplay.com/hc/en-us/community/posts/11074783379991-SPI-problem-with-NHD-3-5-320240FT-CSXN-CTP

To test out the display, I've purchased the NHD-FT81X-Shield.  I have verified that the Sample Sketch App works with NHD-4.3 + Shield + Arduino.
Then, I moved on to interfacing the NHD-4.3 with the MCU for the project, but am not able to get the NHD-4.3 to function/respond to the SPI commands.

To be precise, I am trying to get the 0x7C response from the NHD-4.3, but I can't get it.
I've checked the SPI bus using a scope, and the MCU(nRF52840) is sending the same SPI commands as the Arduino (0x30 0x20 0x00 0x00 0x00).
The only noticeable difference (that I can tell) between the Arduino Setup and the MCU is that the MOSI line is high during idle for the Arduino setup, and low when using the MCU(see attached images).
I read the FT81x spec and it does not seem to specify the MOSI line to be pulled high/low during idle. Does the idle state of MOSI line matter?



Any help is appreciated.

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Comments

3 comments

Date Votes
  • Ted M.
    NHD Staff

    Hi Makoto.inoue,

    The issue from the topic https://support.newhavendisplay.com/hc/en-us/community/posts/11074783379991-SPI-problem-with-NHD-3-5-320240FT-CSXN-CTP was resolved by adding a hardware buffer to the SPI clock source.

    It appears that MOSI goes low once SS is goes low, therefore MOSI is idle High with the Arduino example.  Try this configuration to see if helps.

    Best Regards,

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  • makoto.inoue

    Hi Ted,
    Thank you for the response & suggestion.
    I have solved my issue. 
    The MCU(nRF52840) was not driving the SPI SCLK line enough (I think I was driving SCLK around 0.5mA).
    I changed the MCU pin configuration to drive it higher (0.5mA --> 5mA) and now I’m receiving 0x7C properly. I presume FT813 needs somewhere near 5mA on SCLK to function…

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  • Ted M.
    NHD Staff

    Hi Makoto.inoue,

    It's good to hear you have solved this issue.

    Thanks for posting the solution!

    Best Regards,

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