Adafruit 2.8 TFT, SKU #2090, on Argon

After a rough start, I have the display wired in, coded up and working. Thanks for several threads on different forums and the one here by samuraiken, though it wasn’t as bad as I thought it might be.

I am, however, pretty discouraged by the speed of the display over the SPI. Unfortunately, for my project, it’s just too slow and I don’t have enough IO to support the 8-Bit interface. With that, I will have to just chalk this one up to experience. When I bought the display I thought, how slow could it be? Well, it’s slow slow.

No special libs, just what comes in with a particle library command. There are other devices on this project so I set the interface pins as follows:

#define TFT_DC 6
#define TFT_CS 5
#define TFT_MOSI 12
#define TFT_CLK 13
#define TFT_RST 0
#define TFT_MISO 11

Like I said, it was much easier than I had thought, but because the update rate is so slow, I am going to switch to a Nextion 3.5" Enhanced. That will allow for a nice interface without such a heavy load on the interface. Too bad, cause it is a nice little display and I would have liked to use the cap touch. Live and learn.

When you are defining the SPI pins like this chances are that you are not using hardware SPI but a rather slow software/bit-banging approach.
Without seeing your code it’s hard to tell tho’

What update rate are you expecting?
Will you always rewrite the entire text or rather only replace the actual readings?
What bus speed are you using when talking to the display?
Are you using SPI transactions?
Are you taking advantage of the DMAcapabilities of HW SPI?

I haven’t spent any time digging into the libs, but it probably is bit-banging. They are just the default libs, if you want to see them, just create a dummy app and do a “particle library add Adafruit_ILI9341” and Adafruit_mfGFX. Those are the two I used. I knew it wasn’t going to be fast but I didn’t think it would be so slow.

I tried to blank out just the changed digits, say for instance the time. I would blank the small rect where the seconds are each each time it changed, then the minute when it changed, and so on. Blanking the whole screen before a write makes it unusable.

Like I said, I’ve not looked into the libs, because if just writing a few letters is so painful, the design fails using this device. The Nextion is like having a graphics card and moving that load from the Argon, which has plenty of other things to do.

I’ve been a Photon user for years but this is my first Argon product. I gotta say, I love my Argon…can’t say the same about that tft though.

We’d also like to see your code. The Adafruit_ILI9341 library offers support for both HW and SW SPI - your code makes the choice which to use.

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Too late, I’ve moved on. Thanks for the help.