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Topics - kbless7

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Character LCDs / NHD-C0220BiZ-FSW-FBW-3V3M no display
« on: October 11, 2016, 09:39:28 AM »

I'm trying to communicate to the C0220BiZ with a PicAxe 20M2 microcontroller over I2C. I issue the setup and write commands in the PicAxe program with the built-in functions

Code: [Select]
  pause 1000

  hi2csetup i2cmaster, $78, i2cslow, i2cbyte
  hi2cout 0, ($00)
  hi2cout 0, ($38)
  pause 10
  hi2cout 0, ($39)
  pause 10
  hi2cout 0, ($14)
  hi2cout 0, ($78)
  hi2cout 0, ($5E)
  hi2cout 0, ($6D)
  hi2cout 0, ($0C)
  hi2cout 0, ($01)
  hi2cout 0, ($06)
  pause 10

  pause 500
  hi2cout 0, ($40, %01110011)
  goto main

I have scoped the SCL and SDA lines and attached images of the result. I have tested a slave address of 0x78 and 0x3C per the other threads I have read. The first image shows the i2cout command in the main function where the first burst is the slave address, the second is the comsend, and the last is the data send. It appears that the address of 0x78 works because the ack is low, or low enough, since data transmission continues. If I use 0x3C, the ack is high and nothing else follows.

I have tested the setup with pullup resistors of 1K, 4.7K and 10K. The data bits are sharper with a lower resistance but then the ack bit starts gets higher. The attached images are using a 10K pullup.

I have checked my wiring multiple times. Here are the voltages I'm getting.

1:RST- 3.28V with 4.7K pullup
2:SCL- 3.24V with 10K pullup
3:SDA- 3.24V with 10K pullup
4:VSS- 0V
5:VDD- 3.28V
6:VOUT- 2.93V with 1uF electrolytic cap (I don't have ceramic caps)
7:C1+ 3.28V with 1uF electrolytic cap to C1-
8:C1- 0.02V with 1uF electrolytic cap to C1+

It looks like it isn't initializing since VOUT and C1+ are still near the supply voltage. Does anything look wrong in my code or the images? I followed the startup code in the datasheet for the screen.

Thanks for any help!


If I change the hi2csetup command to be i2cword, VOUT becomes 6.44V, C1+ is 4.85V and C1- is 1.65V. With this nothing is still shown on the display, but do the voltages look correct? I can see all of the dots get dark and then go back to normal upon startup. It doesn't do that when the hi2csetup is set to i2cbyte.

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