ISSUE WHILE READING CHIPID IN DISPLAY (FT813)

Arjun

• June 14, 2019 08:07

Hello,

Issue : Not able to read chip id of the device NHD-7.0-800480FT-CSXV-CTP

Description:

a) Using ATMEGA2560 Controller to communicate with the FT813 driver, AVR Studio is used as IDE

b) SPI and Power connections are given as per datasheet

c) Initialization process is implemented in code, we are able to Power down and Power up the display.  External Crystal                                                              Oscillator command and ACTIVE command can be send to the Device.

d)But, chip id of the device can't be read.

Doubts:

1.) Is SPI communication creates problem? How to check commands written from controller is accepted by the device(FT813)?
2.) I'm reading 2mA in SCLK pin is that a problem? How much mA should be there in SCLK pin?
3) Any Pull up has to be made for MOSI and MISO pins?How much mA should be read from the SPI pins?

0

• 

  Ted M.

  NHD Staff

  • June 18, 2019 08:07

  Hi Arjun,
  
  Please try 5mA on the SCLK. A hardware buffer to provide the extra current has also worked for other users with similar issues.
  
  Best Regards,

  0
• 

  Arjun

  • June 19, 2019 08:07

  Hello,
  
  Thank you for your response Sir. Now we are able to read 5mA in SCLK pin but still not able to read chip id.
  
  Description:
  
  Able to send commands to LCD Driver (FT813), the response for chip id always 0(zero).
  
  What could be the reason? Is that we are missing something in code?
  
  Commands Sent to FT813 from ATMEGA2560:
  
  Code Flow:
  
  1) Port and SPI Initialization
  2) Power-down command
  3) External clock command
  4) Active command
  5) Read REG ID(0x302000)
  
  When Power down command is sent to FT813, display will get enabled(ON) and for Active command it goes to disable(OFF) state. Is this code execution is correct or anything need to be included.

  0
• 

  Ted M.

  NHD Staff

  • June 19, 2019 09:07

  Hi Arjun,
  
  Try reducing the SPI clock to less than 11Mhz before sending the Active command.
  Please see Page 11 of the FT81X Series Programmers Guide for reading the chip identification code and the recommended initialization when booting up the display:
  
  https://brtchip.com/wp-content/uploads/Support/Documentation/Programming_Guides/ICs/EVE/FT81X_Series_Programmer_Guide.pdf
  
  Send Host command “ACTIVE” to enable the clock to the FT81X.
  FT81X starts its self diagnosis process and may take up to 300ms.
  Alternatively, read REG_ID repeatedly until 0x7C is read.
  
  After reset or reboot, the chip ID can be read from address 0xC0000 to 0xC0003.
  
  Best Regards,

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• 

  Arjun

  • June 27, 2019 09:07

  Hello,
  
  Thank you for your response Sir. Now I'm able to read Chip Id.
  
  I have to send two dummy bytes when I'm reading from FT813. I missed one dummy byte so it was not reading chip Id properly. Also I changed 4Mhz frequency to 1Mhz in SPI communication. Now its working fine sir.
  
  Thank you.

  0
• 

  Ted M.

  NHD Staff

  • June 27, 2019 10:07

  Hi Arjun,
  
  It's good to hear you have it working! Thanks for posting your fix to this issue as I know it will help others with a similar experience.
  
  Best Regards,

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