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Topics - ceb4

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Character LCDs / NHD-0420D3Z - Display siezing up
« on: May 02, 2016, 10:01:13 AM »
I am interfacing the NHD-0420D3Z using I2C and a Raspberry Pi model 2. I have put a P82B96 (at +5) between the NHD and Pi to keep the levels at the 0/+5 as the specs call for since I noticed spikes on the SDA above 3.3 when it was directly connected to the Pi. Using a PSO, I am monitoring both sides of the P82B86 to observe both the 3.3 and 5 volt levels. The issue I am having is that a random times (5 minutes to 12 hours) the NHD seizes both the SCL and SDA lines driving them to 0. This is also occurred when I was driving the NHD directly from the Pi. Once seized, the Pi is still pumping out I2C data but the NHD controls both I2C lines and keeps them a zero with the NHD displaying the frozen data. Removing the power and reconnecting it resolves the problem until the next seize. This appears to be a timing issue since another application using a RCM3750 works fine. Anyone have any idea what events would cause the NHD to react this way? I have eliminated the NHD since I have duplicated this problem on multiple NHD's. Thanks in advance.

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