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Messages - asfarley

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It turns out that this was related to an entirely separate issue; our PCB was experiencing some power-stability issues due to a misconfigured GPIO on our MCU. After fixing that, all of this weird flashing-screen behavior disappeared.


We're using NHD-2.4-240320CF-CSXN#-F on a new product. I'm just getting started writing the basic driver.

I'm experimenting with writing solid R/G/B blocks to the screen, and I've noticed a few strange effects:

 * If I fill the entire screen with red or green, it works as expected; if I attempt to fill the entire screen with blue in one shot, the end result is a flashing white image
 * If I fill the screen incrementally with blue (in full-screen-width, 10-pixel-high blocks, step-by-step) then the screen appears completely blue, as expected
 * If I fill the screen with blocks in the order R/G/B (1/3 of the screen is red, 1/3 is green, 1/3 is blue) then I get the flashing-white-screen effect
 * If I fill in the order B/G/R, then I get the correct image
 * Most of the time, while the write operation is in progress, the entire image flashes white
 * I have seen some instances where the screen did not flash white between write operations; not sure what was different in that scenario

Are these phenomena familiar to anyone here?

It feels a bit like blue pixels consume more power, and I'm running into a power-stability issue by setting the entire image blue in one-shot, whereas maybe incremently updating to a 100%-blue image is easier on the power supply. Is that possible? Or is something else going on here?

OLEDs / NHD-0216MW-AB3: no voltage on IREF (pin 22)
« on: December 06, 2017, 05:52:50 PM »
I'm working with an OLED module for a new product. Previously, we used the module NHD-0216MW-SB3 which doesn't include a contrast resistor setting. In our new layout, we use NHD-0216MW-AB3 which doesn't have the same peripheral circuitry as the NHD-0216MW-SB3 module. The display is being used in SPI mode.

The display isn't responding to commands. I believe the SPI commands are correct because they worked on the previous module; both devices use the US2066 internally and they're both running on low-voltage IO logic.

Measuring on IREF, there is no voltage. All the other pins on the OLED module look correct. Here's what I've measured on a multimeter:

1 (VSL) = 0.0
2 (VSS) = 0.0
3 (REGVDD) = 0.0
4 (VDD) = 3.15
5 (VDDIO) = 3.15
6 (BS0) = 0.0
7 (BS1) = 0.0
8 (BS2) = 0.0
9 (/CS) = 3.15
10 (/RES) = 3.15
11 (NC) = 0.0
12 (NC) = 0.0
13 (NC) = 0.0
14 (SCLK) = 3.15
15 (SDI) = 3.15
16 (SDO) = 0.0
17 (NC) = 0
18 (NC) = 0
19 (NC) = 0
20 (NC) = 0
21 (NC) = 0
22 (IREF) = 0
23 (VCOMH) = starts around .06V, slowly drops
24 (VCC) = 9.5

So - where is the IREF voltage (VCC - 4.5) generated? Is this indicative of any common problems?

Is the low/dropping voltage on VCOMH expected? I don't understand what "COM signal deselected voltage" means.

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