Newhaven Display Forum

Newhaven Products => Character LCDs => Topic started by: bwendin on June 25, 2018, 12:22:59 AM

Title: NHD-0220D3Z-NSW-BBW-V3 using I2C dropping characters
Post by: bwendin on June 25, 2018, 12:22:59 AM
We need to control our NHD-0220D3Z-NSW-BBW-V3 with I2C and running at 100kHz (which it says is supported in the datasheet), I see it drop characters.  It seems to drop about one character out of 3 or 4 every time if I send all 20 or 40 with one I2C command.  I looked at the waveforms on a logic analyzer and an oscilloscope and everything looks healthy.  By the way, I'm an I2C expert so I know what healthy looks like.  We are a real company planning to use this display in a production product shipping in Q4 2018.   We just had to switch from UART to I2C after choosing this part and it is hard for us to change at this time.  Any answer as to why it isn't working?   Do I need to run a slow I2C clock (I tried running at 50kHz and it works fine).  But I'm controlling about 5 other parts on same I2C and don't want to run at 50kHz.
Title: Re: NHD-0220D3Z-NSW-BBW-V3 using I2C dropping characters
Post by: Paul_B on July 02, 2018, 09:57:10 AM
Hi bwendin,

Iím sorry to hear about the trouble you are having with the NHD-0220D3Z-NSW-BBW-V3.

There is a known issue on our serial LCD modules which affects its operation when used in I2C mode.
When using the moduleís I2C interface at a clock rate of 100KHz NACKs/bit errors/hanging, may occur.
Therefore, if using the I2C interface of these serial LCD modules, a MAX clock rate of 50KHz should be used.

We have updated the I2C section of our datasheet to reflect this information, and the updated specs should be accessible on our website shortly.
If you have any questions or need any assistance getting these serial LCD modules working, please contact us by emailing our technical support email, or by calling our phone M-F, 8am - 5pm CST (number listed on our website in the contact us section), we're always happy to help!  :D
Title: Re: NHD-0220D3Z-NSW-BBW-V3 using I2C dropping characters
Post by: jimhogue on July 02, 2018, 03:20:27 PM
We are using NHD-C0220BIZ-FSW-FBW-3V3M
It seems to have I2C speed issues and does not ack properly if the pull-up resistors are lower than 10K.  We are using an I2C bus, so we have a bit more capacitance than just the micro to the LCD.  It seems the LCD cannot pull the data line low enough to ack properly.  Is this going to be fixed?