3 * (esp32 + tft) = ?

 

ESP32 boards with a mounted TFT display can be so hard to resist that, in a moment of shameless weakness, I purchased three of them in one buy, without consulting reviews…

 

So here’s a report of my first acquaintances with these new Chinese kids on my block.

 

  LilyGO TTGO T4 v1.3

This board with 8MB PSRAM, an SD card slot and a 2.2″ TFT display makes development of graphics oriented sketches very convenient.

I2C pins are available via a connector (cable included). Unfortunately they didn’t break out the standard SPI pins to the 20 (inconveniently short) pin male header. On my board, different from what some internet pictures suggest, not GPIO25 but GPIO26 is broken out (labeling on the module is correct).

Compared with the LOLIN 2.4″ TFT shield, this display is a bit smaller (with the same resolution) and has no touch screen. Its 3 buttons allow for some basic feedback to the application. Build quality is excellent.

Driving the display was easy, but it took me some time to make it show images from an SD card. That’s because the board’s SD slot requires its own SPI bus on pins 2, 13, 14 & 15. The following code snippets show how I got it working.

In the main section:

 

In setup():

The above code also shows that this board requires you to explicitely switch the backlight on. This can be done by writing HIGH to TFT_BL but I prefer the sigmaDelta method as shown because it lets you control the display’s brightness.

So far, my overall impression of this board and its manufacturer is positive. It would have been perfect with a more Dupont friendly header, including standard SPI pins. Price: €19.


  LilyGo TTGO T-Display v1.1.

The 1.14″ display has 240×135 pixels. To be honest, fontsize 1 starts to become a bit of a visual challenge here, but I do not intend to use this board for text anyway. Actually, I currently have no specific application in mind for it at all, but I’m sure I’ll find one.

Bodmer’s indispensable TFT_eSPI library supports its ST7789 chip, so I expected no less than turbo speed, especially with ‘only’ 32400 pixels to push. Although this ESP32 WROOM module has no PSRAM and less memory than the T4, there’s still enough memory available for double buffering the display.

Information on github is to the point and up to date, so in no time I ported my most recent Webcam·View·Master sketch to this mini display for testing the board.

Note that the real size of the display is only 2.5 x 1.4 cm!

Like with the T4 board, TFT_BL has to be set HIGH in order to switch the backlight on.

Price: €9. Definitely a bargain for an ESP32 with such a cute display. And it even has a LiPo charging circuit and comes with header pins and a battery cable. Make sure you have an usb-C to usb-A cable because that is not included.


M5Stack Core Gray

After my rather negative review for the M5Stack Fire, this purchase may be a bit surprising. Perhaps I secretly hoped that this Gray model wouldn’t have the same issues and annoyances, but that soon turned out to be false hope. Actually, it’s even more noisy than the Fire and my dacWrite(25, 0) trick doesn’t change that. It is, however, less sensitive to usb power issues during sketch uploads. No ‘brown out detections’ so far.

But then, ESP32 development boards don’t come any better looking than the M5Stack family. Once you can work around its electronic design flaws, the Gray makes a perfect housing for ESP32 gadgets, especially when combined with a matching standing base power supply, equipped with a DHT12 temperature and humidity sensor.

I found a DHT12 library and an example sketch for reading the DHT12 sensor here, but the example didn’t compile. Here’s a corrected version that displays temperature and humidity when an M5Stack Core model is put on the standing base.

 

Compared with the Fire, the Gray has no Neopixel led bars and no PSRAM, making three extra GPIO pins availabe for other purposes, including GPIO16 and GPIO 17 for UART communication. Its battery is only 150 mAh, but I don’t mind because I couldn’t resist that standing base either. Prices: €30 for the Gray and €7.50 for the standing base.


Epilogue

The two LilyGo boards were my first from this manufacturer (is Lily Zhong the Chinese LadyAda?). I like both displays, so they will not be the last TTGOs.

As for the M5Stack ecosystem: now that I have everything I need for making great looking gadgets, I don’t think I’ll invest in it any further. Maybe they should ask some seasoned analog nerd to improve their electronic design with a couple of dirt cheap components.