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@drdnar
If you know, you know.

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TIâs TL431 datasheet is amazing. Their engineers clearly love the over-40-years-old part. The examples section makes it sound like it can do nearly anything short of make you coffee.
A Color LCD (displaying garbage)
Iâm not sure what I expected a data test pattern to look like, but it wasnât this. But I have confirmed something I feared: the display is actually portrait orientation.
the upside of ADHD is that it makes you a fucking genius
the downside is that you don't get to decide when and for how long you're a genius.
Well it's time to hook up the LCD to signals and see if it can actually display anything. It's entirely possible that it got fried by ESD while sitting in a box for years. It's equally possible that I just have no idea what I'm doing!
Case in point: I assumed VCOM meant another ground potential, but after just now looking more closely at the datasheet, it actually appears to be some kind of analog (contrast?) adjustment.

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A Color LCD (part 2)
Today I finished and built the LCD case. The case is made of 0.5Â mm cardstock and 2.2Â mm cardboard, both upcycled product packaging. To make it, I drew up template artwork in Adobe Illustrator CS5.5 (Iâm using that perpetual license until I die and Adobeâs SaaS can die in a fire), printed it, taped it over cardstock and cardboard, and then used a knife to cut up the cardstock and cardboard according to the template. Illustrator is definitely not a CAD package, but fortunately, I still remember how to do basic trigonometry and 2D vector math, with a little help from a TI-84 Plus CE. (I may be somewhat nerdy.)
Pictures below.
A Color LCD (part 1)
Many years ago, I pulled an LCD out of a GPS unit from the days before cars and smartphones having navigation features. This LCD is a color LCD with a backlight. Itâs a very different technology, and much more challenging to interface to. I canât even find a proper datasheet for the module.
B&W LCDs
One of my recent hobbies has been pulling LCDs out of old devices and trying to get them to work. So far, Iâve gotten two B&W LCDs from old cell phones working.
I happen to like black and white LCDs. Theyâre a good compromise between being sunlight-readable, low-power, and updating fast. They consume mere milliwatts but unlike e-ink displays, can still display smooth graphics.
Most panels have a chip-on-glass (COG) integrated circuit of some kind. As the name suggests, itâs a silicon microchip epoxied directly on the same glass substrate as the LCD matrix. The chip acts as the interface between digital logic and the physical pixels on the LCD. The pixels themselves are analog things that require special driving signals with odd voltages and need to be refreshed several times a second or else the image fades; the driver chip takes care of all that. Depending on the application, the COG may have on-chip graphics memory (GRAM), so a microcontroller need not continuously resend image data.
Most B&W LCDs use an older pixel technology call super-twisted nematic that results in somewhat blurry motion. Essentially, it takes a non-zero amount of time for a pixel to change state, and for STN, that time is typically tens of milliseconds. The upshot of this, however, is that if you rapidly change a pixel between black and white, it never has time to finish switching to fully-dark or fully-light. Instead, it just oscillates at an in-between gray level. Based on some code by Wenting Zhang, Iâve managed to get grayscale working on my B&W LCDs.
Do I need to add an external capacitor for this LCD module?
Yeah I guess it needs a capacitor.
When you own an oscilloscope, you can just hook it up to things to see what's happening inside.
I got a little 150Â W inverter (nominal 110Â VAC out) for powering my laptop in a car. I can say that it meets or exceeds minimum standards for quality and safety. As advertised, the high-voltage output is fully-isolated. Also as-advertised, if you squint at the oscilloscope trace, you can see the modified sine wave output. This is different than a 400Â W inverter I had that produces â150Â V pulses on alternating pins and is not isolated.
A few months ago, I got a USB-C PD charger that looks a little suspiciously cheap to me. The USB-C output actually worked OK: no noise, acceptable but unimpressive regulation. But the type-A port was garbage:
This is supposed to be 5 VDC, and it should handle > 2 A, but this is only a 1.6 A load. It should show 4.75â¤RMS[1]â¤5.25 so 4.68 V is out-of-spec and 880 mV peak-to-peak is way too much noise (the line should not have those spiky bits).

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