The hardware I2C for second display with WiFi LoRa 32 (V2)

Tomasz_Fularski · July 24, 2019, 11:09pm

I know. I know. Dev-board with OLED display is made to use this display, instead of disconnecting it :-).
You wrote about OLED in WiFi LoRa 32 (V2): “can be used to display debugging information, battery power, and other information”. But I need to connect to this Dev-board a much larger display. The original, 0, 96" can work but does not have to. Now I have both displays connected and working, but the larger display is connected via software I2C. So it is very slow.

I do not know if I read the Dev-board pinout diagram well, I do not see the possibility of connecting a second display through the hardware I2C port. But I can be wrong.

Can I “turn off” this 0.96 ‘’ OLED display and use the SPI pins that are now used by it?

Tomasz

Supporter · July 25, 2019, 2:24am

Refer to this example code to use another hardware I2C bus.

github.com

HelTecAutomation/Heltec_ESP32/blob/master/examples/ESP32/I2C_Scanner/I2C_Scanner.ino

/* Heltec Automation I2C scanner example (also it's a basic example how to use I2C1)
 *
 * ESP32 have two I2C (I2C0 and I2C1) bus
 *
 * OLED is connected to I2C0, so if scan with Wire (I2C0), the return address should be 0x3C.
 *
 * If you need scan other device address in I2C1...
 *		- Comment all Wire.***() codes;
 * 		- Uncomment all Wire1.***() codes;
 *
 * I2C scan example and I2C0
 *
 * HelTec AutoMation, Chengdu, China
 * 成都惠利特自动化科技有限公司
 * www.heltec.org
 *
 * this project also realess in GitHub:
 * https://github.com/HelTecAutomation/Heltec_ESP32
 * */

This file has been truncated. show original

The Onboard OLED uses I2C0 (Wire), for another I2C display, you can use I2C1 (Wirel1).

Tomasz_Fularski · July 25, 2019, 5:02am

. There is nothing connected to the Dev-board.

But, if the attached code would show me the correct address, which Dev-board pins are marked SDA and SCL? I know that SDA_OLED is GPIO4 and SCL_OLED is GPIO15.

Tomasz

Tomasz_Fularski · July 25, 2019, 5:09am

To be sure, here is the code with the changes, that gives the above record from the Serial.

Aaron · July 26, 2019, 6:42am

Because you didn’t connect any device on the I2C bus, so can’t get any address feedback. The attached code just show you how to config use another I2C bus.

ESP32 have IO_MUX function, any GPIO can be config to I2C bus.

Tomasz_Fularski · July 26, 2019, 7:16am

Before running this code, the second display was attached.

Tomasz_Fularski · July 26, 2019, 9:47am

I even tried on a few free ports. each time in Wire1.begin enter the GPIO to which the second display was connected. When I connect this display to the same GPIO with software I2C , it works.

Supporter · July 28, 2019, 6:30am

You mean the system can detect another display, but can’t make it running?

Tomasz_Fularski · July 28, 2019, 10:46am

Thanks for the answer. Exactly. I guess it’s a matter of using the olikraus u8g2 library, not the problems with the Heltec Dev-Board.

As Olikraus writes, his u8g2 library is based on the Arduino Wire library. If I understand correctly when using Wire1, there is no simple way to specify the port numbers to which the display is connected. Unfortunately, my knowledge is too small to change something in .h or .cpp files. I asked olikraus for help, I hope that thanks to his help I will be able to use the second display connected through the hardware I2C.

Tomasz

Tomasz_Fularski · July 28, 2019, 11:35am

I have a question about your I2C scanner. Both for Wire and for Wire1, your scanner shows exactly the same address - 0x3C. (I enclose the pictures, so as not to confuse the entries, I added “on Wire” and “on Wire1” to the information displayed by the scanner.)

On the display, I have the option to change the address, but they are completely different - 0x7A or 0x78.

Maybe this is normal, but none of this is clear to me :-(.

Supporter · July 29, 2019, 2:52am

Because OLED’s I2C register is 7 bits, ESP32 have a 8 bit I2C register. So:
0x3C == 0x78 >> 1

Tomasz_Fularski · July 29, 2019, 9:05am

It seems that connecting two displays to this Dev-board is not easy at all. Here is what olikraus wrote to me:

One precondition for the second I2C interface is a proper definition of WIRE_INTERFACES_COUNT by the ESP32. The value for WIRE_INTERFACES_COUNT must be 2 or higher, denoting, that there is an additional Wire object called “wire1”.

github.com

olikraus/u8g2/blob/master/cppsrc/U8x8lib.h#L113


#ifdef U8X8_HAVE_HW_I2C
#undef U8X8_HAVE_HW_I2C
#endif 
#endif




/* define U8X8_HAVE_2ND_HW_I2C if the board has a second wire interface*/
#ifdef U8X8_HAVE_HW_I2C
#ifdef WIRE_INTERFACES_COUNT
#if WIRE_INTERFACES_COUNT > 1
#define U8X8_HAVE_2ND_HW_I2C
#endif
#endif
#endif /* U8X8_HAVE_HW_I2C */


/* define U8X8_HAVE_2ND_HW_SPI if the board has a second wire interface*/
/* As of writing this, I did not found any official board which supports this */
/* so this is not tested (May 2017), issue #224 */
/* fixed ifdef, #410, #377 */
/* meanwhile it is defined e.g. here: https://github.com/arduino/ArduinoCore-samd/blob/master/variants/mkrzero/variant.h#L91 */
/* so it should be available for mkrzero */

If this interface count is only 1, then the 2nd wire interface callback evaluates to the empty function (and obviously will not do anyting): https://github.com/olikraus/u8g2/blob/master/cppsrc/U8x8lib.cpp#L1182

EPS32 defines a Wire1 object: https://github.com/espressif/arduino-esp32/blob/master/libraries/Wire/src/Wire.h#L137
However, it does not tell, that such an object exists.

Compare, for example STM32 Arduino software: https://github.com/rogerclarkmelbourne/Arduino_STM32/blob/master/STM32F1/libraries/WireSlave/src/Wire_slave.h#L37

As a workaround we could check for ESP32 environment (question: How to do this?) and enable the 2nd I2C interface.

Maybe this works. After this line

github.com

olikraus/u8g2/blob/master/cppsrc/U8x8lib.h#L130


/* so this is not tested (May 2017), issue #224 */
/* fixed ifdef, #410, #377 */
/* meanwhile it is defined e.g. here: https://github.com/arduino/ArduinoCore-samd/blob/master/variants/mkrzero/variant.h#L91 */
/* so it should be available for mkrzero */


#ifdef SPI_INTERFACES_COUNT
#if SPI_INTERFACES_COUNT > 1
#define U8X8_HAVE_2ND_HW_SPI
#endif
#endif




extern "C" uint8_t u8x8_gpio_and_delay_arduino(u8x8_t *u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr);
extern "C" uint8_t u8x8_byte_arduino_8bit_8080mode(u8x8_t *u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr);
extern "C" uint8_t u8x8_byte_arduino_4wire_sw_spi(u8x8_t *u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr);
extern "C" uint8_t u8x8_byte_arduino_3wire_sw_spi(u8x8_t *u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr);
extern "C" uint8_t u8x8_byte_arduino_hw_spi(u8x8_t *u8g2, uint8_t msg, uint8_t arg_int, void *arg_ptr);
extern "C" uint8_t u8x8_byte_arduino_2nd_hw_spi(u8x8_t *u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr); /* #244 */
extern "C" uint8_t u8x8_byte_arduino_sw_i2c(u8x8_t *u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr);
extern "C" uint8_t u8x8_byte_arduino_hw_i2c(u8x8_t *u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr);
extern "C" uint8_t u8x8_byte_arduino_2nd_hw_i2c(u8x8_t *u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr);

add the following code:

#if defined(ARDUINO_ARCH_ESP32)
#define U8X8_HAVE_2ND_HW_SPI
#endif

—

Tomasz_Fularski · July 29, 2019, 9:13am

Maybe if I used a different library to operate the second display, connecting it to WiFi LoRa 32 would be easier. However, the u8g2 library has many advantages. I can not find any similar.

I am thinking of changing the LoRa module to one without a display. In order not to change an almost ready, large program, I would need dev-board with ESP32, the option of connecting and charging the battery and - of course - without a display.
In your offer according to the table:

meets these conditions only “Wireless Stick Lite”, but… in its technical specification is information that it has a display:

Which Wireless Stick Lite description is true?

Supporter · July 31, 2019, 10:43am

I wrote a simple code to drive two display, just connect the second display with the main display in the same I2C bus (SDA – GPIO4, SCL – GPIO15):

#include "Arduino.h"
#include "heltec.h"

void setup()
{
	Heltec.begin(true, false, true);
}

void loop()
{
	Heltec.display->init();
	Heltec.display->flipScreenVertically();
	Heltec.display->setFont(ArialMT_Plain_10);
	Heltec.display->drawString(20, 20, "Hello display 0");
	Heltec.display->display();

	delay(2000);

	Heltec.display1->init();
	Heltec.display1->flipScreenVertically();
	Heltec.display1->setFont(ArialMT_Plain_10);
	Heltec.display1->drawString(20, 20, "Hello display 1");
	Heltec.display1->display();
	delay(2000);
}

You need also fix the library source code:

And you need to fix the second display’s I2C address:

Tomasz_Fularski · July 31, 2019, 12:26pm

I am truly grateful for your time.
But … my display is 128 x 128, not 128 x 64, and it has a different display controller - SSD1327, not SSD 1306.

Tomasz_Fularski · July 31, 2019, 12:39pm

Now, both displays are visible:

Serial initial done
you can see OLED printed OLED initial done!
Scanning…
I2C device found at address 0x3C !
I2C device found at address 0x3D !
done

Supporter · August 1, 2019, 2:09am

What I provide is a solution to the problem, you can solve your own problems according to the ideas.

Tomasz_Fularski · August 1, 2019, 5:11am

OK Thanks. And wat with display in Wireless Stick Lite? Which site of your website is telling the truth? Is there a display or not?

Supporter · August 1, 2019, 8:04am

Oh, I had fixed that mistake, sorry for forgot to tell you.

There is no display on the Wireless Stick Lite

shakya12345 · June 13, 2021, 4:04am

so how can we use OLED 0.96’ with wireless stick lite?Does it support OLED display?

The hardware I2C for second display with WiFi LoRa 32 (V2)

It seems that connecting two displays to this Dev-board is not easy at all. Here is what olikraus wrote to me:

Now, both displays are visible:

Serial initial done you can see OLED printed OLED initial done! Scanning… I2C device found at address 0x3C ! I2C device found at address 0x3D ! done

Serial initial done
you can see OLED printed OLED initial done!
Scanning…
I2C device found at address 0x3C !
I2C device found at address 0x3D !
done