Problem with NHD 0420CW AY3 Display

jglledo

• October 27, 2015 05:37

Hi,
I am currently working with the NHD 0420CW AY3 Display using I2C protocol. I am receiving ACK responses, but in spite of that my display still remains turned off.
I have tried with the init sequence listed in the datasheet example.

I have some doubts about some pin connections, when using 5volts mode, I write below my connection scheme:
 - 1 (VSS) -->  Ground
 - 2 (VDD) --> 5 volts
 - 3 (REG_VDD) --> 5 volts
 - SA0  --> Ground
 - 5 to 6 Not connected
 - 7 --> SCL
 - 8 and 9 tied together ---> SDA
 -10 to 15 Not connected
 -16 (RES) --> 5 volts
 -17 -19 ---> Ground - 5 volts - Ground (I2C Mode)
 -20 --> Ground

**Should I use any pull up resistor for SDA /SCL? (which value) ?

Any suggestion?

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  Saurabh_B

  • October 27, 2015 15:16

  The pullup resistors will depend on the MPU you are using. If it does already have pull up resistors built in (Like the arduino Mega) you wouldn't need any. But we prefer using 10k resistors if they aren't on the input lines. 
  
  Can you tell me what slave address you are using, and if you are enabling the internal voltage regulator for 5V.
  
  The pins that are no connects should be tied to ground.

   

  « Last Edit: October 29, 2015, 01:22:55 PM by Saurabh_B »

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  jglledo

  • October 28, 2015 03:46

  Hi,
  the slave address I am using is: 0x3C as SA0 pin is connected to ground.
  b7 b6 b5 b4 b3 b2 b1           b0
  0   1    1   1   1   0  SA0=0  R/W#
  In the initialization sequence I thin I do enable the internal regulator, as I send next commands:
   command(0x2A)
   command(0x71)
   data(0x5C) ---> this is to enable the internal regulator for 5 volts, isn't it?
  
  In the case of sending a command I send next I2C signals
  
  0x3C | 0x 80 | Command byte
  start 0x3C ACK stop | start 0x80  ACK stop | start Command byte ACK Stop
  
  In the case of sending a data byte I send next I2C signals
  0x3C | 0x 40 | data byte
  start 0x3C ACK stop | start 0x40  ACK stop | start Data byte ACK Stop
  
  I have also tied pins that were not connected to ground.
  At this moment I don't know if I have damaged the display, because now I am not able to talk to it by I2C...

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  Saurabh_B

  • October 28, 2015 11:53

  Any chance you would be able to upload your initialization sequence?

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