Author Topic: Difficulty with SPI with NHD-4.3-480272FT-CSXV-CTP  (Read 921 times)

makoto.inoue

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Difficulty with SPI with NHD-4.3-480272FT-CSXV-CTP
« on: October 30, 2018, 12:22:43 AM »
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://www.newhavendisplay.com/NHD_forum/index.php/topic,8363.0.html

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.
« Last Edit: November 01, 2018, 10:01:40 PM by makoto.inoue »

Ted_M

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Re: Difficulty with SPI with NHD-4.3-480272FT-CSXV-CTP
« Reply #1 on: November 01, 2018, 03:56:10 PM »
Hi Makoto.inoue,

The issue from the topic https://www.newhavendisplay.com/NHD_forum/index.php/topic,8363.0.html 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,

makoto.inoue

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Re: Difficulty with SPI with NHD-4.3-480272FT-CSXV-CTP
« Reply #2 on: November 07, 2018, 08:00:22 PM »
Hi Ted,
Thank you for the response & suggestion.
I have solved my issue. 8)
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…

Ted_M

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Re: Difficulty with SPI with NHD-4.3-480272FT-CSXV-CTP
« Reply #3 on: November 08, 2018, 10:07:16 AM »
Hi Makoto.inoue,

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

Thanks for posting the solution!

Best Regards,

 

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