80x160 TFT display with the nrf9160 on SPI and ST7735 driver

RE: 80x160 TFT display with the nrf9160 on SPI and ST7735 driver

helsing — Tue, 28 Feb 2023 11:55:17 GMT

Hello Brendel,

Thank you for your question. As this is a new topic, please open a new ticket and post your issue there, and we will reply in the new case. Please refer to the relevant parts of this case and also include which nRF Connect SDK version you are using.

RE: 80x160 TFT display with the nrf9160 on SPI and ST7735 driver

Brendel V. — Fri, 24 Feb 2023 15:11:47 GMT

i'm trying to implement st7735s 3pin SPI driver based on existing st7735r driver.

I used Nrf Connect zephyr/out-of-tree driver example.

Adding custom display driver gives such error: No SOURCES given to Zephyr library: drivers__display on project build stage.

My project:

https://1drv.ms/u/s!AnME8YPmGyyIhKY9lyvfJ7lfmxA6aQ?e=BJPSb0

I there a way to enable custom out-of-tree lcd driver working with zephyr lcd API for freestanding application?

RE: 80x160 TFT display with the nrf9160 on SPI and ST7735 driver

helsing — Wed, 11 Jan 2023 14:31:27 GMT

Would you be able to upload your current project? I could capture the startup sequence with a logic analyzer.

RE: 80x160 TFT display with the nrf9160 on SPI and ST7735 driver

helsing — Fri, 06 Jan 2023 13:44:56 GMT

Thank you for the update.

[quote user="Tor Kaufmann"]but the initial code needs to be updated according to its IC to get the best display effect.[/quote][quote user="Tor Kaufmann"]I will most definitely do a logic comparison with the ESP32 board that has the TFT working with the Adafruit library to see if I can spot any difference in the physical signals on the SPI bus.[/quote]

Yes, this will be interesting to see.

RE: 80x160 TFT display with the nrf9160 on SPI and ST7735 driver

Tor Kaufmann — Thu, 05 Jan 2023 19:52:50 GMT

Hi again Helsing,

The search and debugging in order to get this TFT working with the nrf9160 continues.

I have an update from Sitronix,

Quote:

"... ST7735R is an old IC. It has been EOL and has been replaced by ST7735S for supply.
ST7735R needs to add capacitor parts on the FPC side, while ST7735S does not.
Both commands are compatible, but the initial code needs to be updated according to its IC to get the best display effect."

End quote.

So the ST7735R driver "should" be able to work with the newer S-version.

I will most definitely do a logic comparison with the ESP32 board that has the TFT working with the Adafruit library to see if I can spot any difference in the physical signals on the SPI bus.

I find it strange that the ST7735R library is not working when I can see the settings in the .overlay file matches the settings in the Adafruit library.

RE: 80x160 TFT display with the nrf9160 on SPI and ST7735 driver

helsing — Thu, 15 Dec 2022 14:19:56 GMT

Thank you for the update.

Do you have any logic analyzer available? It would be interesting if you could record the startup sequence from both nRF9160 as well as the other board. You could then compare the two to look for differences.

[quote user="Tor Kaufmann"]About the difference of the R and S version I have reached out to Sitronix for a comment.[/quote]

It will be interesting to see if there are any significant differences.I found the datasheets, however, I have not yet compared the two in detail.

https://www.crystalfontz.com/controllers/Sitronix/ST7735S

https://www.crystalfontz.com/controllers/Sitronix/ST7735R

RE: 80x160 TFT display with the nrf9160 on SPI and ST7735 driver

Tor Kaufmann — Sun, 11 Dec 2022 15:57:11 GMT

Hi again Håkon,

I have the terminal printing "updated display" once every second. From main.c we see that this is after we have a screen write/update. No errors printed.

About the difference of the R and S version I have reached out to Sitronix for a comment.
Some of the differences are listed here: https://www.sitronix.com.tw/en/products/aiot-device-ddi/

In regards to the adafruit library Its a bit difficult to decipher if its written for a specific version. Code and comment are somewhat contradicting Adafruit-ST7735.

However since the MCU seems to be writing data on the SPI bus, and we have something going on on the screen (prints different versions of garbage to the screen on the first few updates before turning blank - see first picture in post for what I refer to as garbage). I though to look into the format of the actual data written.

Ive compared the Adafruit library for the "INITR_MINI160x80" as this is the settings that works for the display using the ESP32. The .overlay file is changed slightly in order to replicate the Adafruit driver settings: Adafruit-ST7735

The following is now in the .overlay file:

 / {
	chosen {
		zephyr,display = &st7735r_st7735r_ada_160x128;
	};
};

&arduino_spi {
	compatible = "nordic,nrf-spim";
	status = "okay";
	cs-gpios = <&gpio0 10 GPIO_ACTIVE_LOW>; /* D10 */
	pinctrl-0 = <&spi3_default>;
	pinctrl-1 = <&spi3_sleep>;
	pinctrl-names = "default", "sleep";

	st7735r_st7735r_ada_160x128: st7735r@0 {
		compatible = "sitronix,st7735r";
		spi-max-frequency = <1000000>;
		reg = <0>;
		cmd-data-gpios = <&gpio0 31 GPIO_ACTIVE_LOW>;	
		reset-gpios = <&gpio0 20  GPIO_ACTIVE_LOW>;
		width = <80>;
		height = <160>;
		x-offset = <0>;
		y-offset = <0>;
		madctl = <0xC0>;
		colmod = <0x05>;
		caset = [00 00 00 4F];
		raset = [00 00 00 9F];
		vmctr1 = <0x0e>;
		invctr = <0x07>;
		pwctr1 = [a2 02 84];
		pwctr2 = [c5];
		pwctr3 = [0a 00];
		pwctr4 = [8a 2a];
		pwctr5 = [8a ee];
		frmctr1 = [01 2c 2d];
		frmctr2 = [01 2c 2d];
		frmctr3 = [01 2c 2d 01 2c 2d];
		gamctrp1 = [02 1c 07 12 37 32 29 2d 29 25 2b 39 00 01 03 10];
		gamctrn1 = [03 1d 07 06 2e 2c 29 2d 2e 2e 37 3f 00 00 02 10];
	};
};

Ive added the:

caset = [00 00 00 4F];
raset = [00 00 00 9F];
invctr = <0x07>;

and changed

madctl = <0xC0>;
colmod = <0x05>;

The display is however still printing garbage the first few updates before turning blank.

RE: 80x160 TFT display with the nrf9160 on SPI and ST7735 driver

helsing — Wed, 07 Dec 2022 13:54:40 GMT

Have you checked the terminal to see if there are any error messages?

RE: 80x160 TFT display with the nrf9160 on SPI and ST7735 driver

helsing — Wed, 07 Dec 2022 13:53:16 GMT

[quote user=""]what would be the best way to define CPOL/CPHA in code when using the ST7735 driver.[/quote]

Please see the flags in the SPI API. Some SPI flags are defined in the ST7735 driver. As CPOL/CPHA are not defined here, they are likely not needed. However, it would not hurt to give it a try.

I noticed that your display module is populated with ST7735S, however, the driver you are using is named st7735r. There are three parts from Sitronix with similar names, ST7735, ST7735R and ST7735S. I do not know exactly what the differences are and whether it is causing any problems.

[quote user=""]Ive tested the TFT with an ESP32-C3 mini in the Arduino environment and confirmed that the display is working fine with same wiring as used for the nrf9160 setup.[/quote]

Is this driver specifically written for the -R or the -S version?

[quote user=""]However the result I get on the TFT display is still just garbage.[/quote]

Is the garbage the same every time? Does it keep changing when the application is running?

RE: 80x160 TFT display with the nrf9160 on SPI and ST7735 driver

Tor Kaufmann — Mon, 05 Dec 2022 19:38:15 GMT

Thanks a lot Håkon:)

RE: 80x160 TFT display with the nrf9160 on SPI and ST7735 driver

helsing — Mon, 05 Dec 2022 13:58:43 GMT

Hi Tor,

Just letting you know I have received the case. I will take a look at get back to you.

Best regards,

Håkon