Project 36:
ESP32 Remote Sensor

v6.0 ESP32 (DOIT DevKit-C v4): Schematic, Board Layout, PCB Top and Bottom

v6.0 Bill of Materials

Demo of Prototypes SH110x and ST7789 Displays

The v6.0 PCBs will be sent out for fab once the breadboard proves out.   

Overview:

ESP32 development unit hosts a WiFi web server to share temperature, humidity and barometric pressure. They can be placed in various locations and accessed via a web page.

Additionally, WiFi MAC address and IP address are displayed.

v6.0: DOIT ESP32 DevKit-C v4 with AliExpress_2.0" Colour IPS_Display or 1.3" OLED

Arduino Code:

v4.1 ESP32  with ST7789_2.0"_Colour_IPS_TFT_or_SH1106 1.3" OLED display and BME280 sensor

v6.0 BME280_OLED_RGB_SNTP_SD.ino

Note: If your ESP32 ever locks up, try this code: Reset_ESP32.ino

We have designed a PCB to accommodate a number of devices. If you wish to learn how things work while assembling the PCB then I suggest you get yourself a quality breadboard, jumper wires and follow the directions below.

The PCB will contain the following:
- DOIT ESP32 Devkit-C v4 with WiFi
- 1.3" mono OLED display or 2.0" colour IPS display
- BME280 or AHT10 sensors (temperature, humidity, barometric pressure)
- RGB 3-colour LED
- Adafruit #4682 SD drive
- Adafruit #4667 PIR motion sensor
- Adafruit #2124 LiPoly battery charger

We'll start off by testing the  I2C Devices: If you install two rows of 19-pin sockets (or a single 38-pin double socket or cheaper 40-pin double socket) for each side of the ESP32, you can connect it via the spare pin sockets to a breadboard: the 38-pin ESP32 is too wide to be used on a standard breadboard.
We are going to test several modules separately. If successful we'll test a few together to ensure continued success. If something does not work we can quickly revert to the config where it just worked.
The schematic above contains a microcontroller pin inventory in green text, organized by device/module then pin number.
The 1.3" OLED display,  BME280 sensor and AHT10 sensor use 3v3 and I2C. I use yellow jumper wire for SCL and blue jumper wire for SDA because they're easy to pick out on the breadboard.

SCL on the ESP32 is pin 22 and SDA is pin 21. If the two I2C devices you're using are designed "properly", they already contain pullup resistors on SCL and SDA. All of these type of sensors I have looked at had SMT resistors marked as 103 indicating they were 10k. They also had a 100nF noise coupling cap on the power supply pin.

Let's start by checking the I2C address of the OLED using the Serial Monitor and the scanner sketch I2C_Scan.ino
- OLED I2C address is 0x3c
Remove the OLED and install the BME280 sensor. Run the scanner sketch again.
- BME280 I2C address is 0x77

Remove the BME280 sensor and install the AHT10 sensor. Run the scanner sketch again.

- AHT10 I2C address is 0x38

If you install all 3 devices, you should be able to see them all listed in the Serial Monitor as shown here.

If one of the devices tested separately is not showing up, consider changing to one of the alternative I2C addresses. For the BME280 that could be 0x76 instead of 0x77.

I2C is now tested.

Remove the sensors. We'll use an Adafruit sketch, SH1106_128x64_i2c_QTPY.ino, to test the OLED for graphics and text.
Results should be seen on the OLED and on the Serial Monitor as shown here. 

OLED is now tested.

Remove the OLED, install the BME280 sensor, load and run the sketch, BME280_Test.ino.  Results can be seen in the serial monitor and here.

Remove the BME280, install the AHT10 sensor,  load and run the sketch, AHT10_Test.ino.  Results can be seen in the serial monitor and here.
Troubleshooting: If you get serial monitor outputs with "nan" instead of a numerical value from the sensor, check your grounds. Or you may have the wrong I2C address: address 0x77 is commonly used but some offshore clones use address 0x76.
If the device is working but the values are erratic, then it may not be terminated properly. Consider adding a 10K resistor to VCC for SCL and another to VCC for SDA but this is a last resort as it is most likely not necessary.

Your sensors are now tested.

We have separately tested the OLED display and the BME280 or AHT10 sensors, so now let's test them at the same time. Load up and run the sketch BME280_OLED.ino
The same global variables and setup parameters from the two previous sketches, I2C_Scan.ino and BME280_Test.ino, can be found in BME280_OLED.ino
Some additional features have been added:
- Line 6: added WiFi driver so we can get the ESP32's wireless Ethernet (WiFi) MAC address and IP address
- Lines 16 to 20 are not needed until we attach an SPI-based microSD card interface but we'll keep them in for now as a way to reserve the ESP32 pin assignments
- Lines 27 to 29 are not needed until we install the PIR motion detection device
- Lines 36 and 37 will be used to automatically login to our preferred WiFi network
- Lines 55 to 59 show the WiFi network connection attempt. Periods will be displayed in the Serial Monitor until we are connected
- Lines 61 to 68 will print our wireless Ethernet (WiFi) MAC address, IP network address, and network name or SSID in the Serial Monitor
- Lines 69 and 70 have been commented out for now but we'll use them later to configure the ESP32 as a web server
In Loop() we have six functions performed sequentially that will display on both the 1.3" OLED and the serial monitor. You can see the Serial Monitor results here. You may notice in the code that Line4() has been commented out. That's because the formula for calculating Humidex or Heat Index (USA) is not working - it's only displaying the current temp.

OLED_BME_RGB.ino is our next test file. It contains everything from BME280_OLED.ino and we've added the following to test an RGB LED:
- Lines 22 to 27 in the global variables section above the setup() section, show the ESP32 pins that are assigned to the RGB LED as well as the 8-bit values associated with On and Off
- Lines 51 to 53 define the pins as outputs. Note how this is markedly different from line 28 of File|Examples|01.Basics|Blink.
- Lines 85 and 86 call two functions to first turn off the LEDs, then cycle them thru On and Off. The two functions are at the bottom of the Loop() code

An example from the Serial Monitor can be found here.

The RGB LED is now tested.

Troubleshooting:
If any sketch refuses to be uploaded to the ESP32, make sure Serial Monitor (SM) is running beforehand. If not then push the board's RESET button or restart the upload or both; the key point is we need SM running. Within SM you may see the ESP32 "going crazy". If so remove power to it briefly then upload the RGB.ino sketch to the ESP32 to stabilize it. It's best if the RGB.ino sketch is the ONLY one open at the time.

Now that it has stabilized close RGB.ino, upload and run OLED_BME_RGB.ino again. Make sure SM is running before you start the upload to the ESP32.

OLED_BME_RGB_Time.ino is our next sketch. Here is an example of it working on the Serial Monitor.
Thus far we have sequentially installed and tested 3 hardware modules: OLED display, BME280 or AHT10 sensor and RGB LED. Now we'll add in a request for the local time, not the global time which will require the use of SNTP and HTTP communication protocols over WiFi to get the current time.
The sketch (File|Examples|Examples from Custom Libraries|SD|SD_time) found in the Examples menu or the modified file SD_time_TEST.ino contain the content we'll graft into a new file, BME_OLED_RGB_Time.ino
Changes to the new file include:
- Reorganized the global variables section above setup() to keep all of the related drivers and parameters together
- Line 29 was added for the local time drivers (https://www.tutorialspoint.com/c_standard_library/time_h.htm)
- Line 32 shows the sntp.h file being included for when we perform a global time lookup at a later time
- In setup() both the Serial Monitor and the OLED are given a one-second startup time: lines 55 and 58
- The MAC (WiFi physical) address as well as the WiFi network name and IP address are printed on the Serial Monitor in lines 80 to 87
The main code loop aptly named loop() contains several routines:
- In the first function, Line0(), "Tiny Sensor Server" is displayed on the OLED and SM (Serial Monitor)
- In the second function, smTime(), the current local time is only displayed on the SM because there is not enough room. We will display it on the IPS display later
- Functions Line(1) through Line(4) are the same as earlier

- The next function EthIP displays both the WiFi MAC and IP addresses on both the OLED and SM

- In the next function, RGBLEDs_Off(), the three RGB LEDs are turned off.

- In the final function, RGBLEDs_OnOff(), the three LED colours are cycled on and off

The local Time function is now tested.

BME280_OLED_RGB_SNTP.ino contains all of the previous code. Code has been added so that the network time protocol (SNTP protocol) is used to accurately update the current time. Here is an example of it working on the Serial Monitor.

The following lines were added:

- 29 to 32: drivers, time zone and daylight savings time offset

- 95 to 100:  Can get IP address from DHCP server or the others configured in configTime(). When current time is updated via SNTP, another function timeavailable() can run. It is found in lines 221 to 223.

ConfigTime() specifies offset from UTC/GMT, daylight savings time, and two NTP time servers. Lines 36 and 99 accomplish the same thing

- 105: function netTimeOLED() of lines 208 to 219 is called which displays the time in the Serial Monitor and on the OLED after clearing it

The SNTP network time function is now tested.

BME280_OLED_RGB_SNTP_SD.ino contains additional SD drive code. You MUST use the ESP32 SD and FS drivers or expect trouble during compilation. The driver set can be found here: https://github.com/espressif/arduino-esp32   Info on installing the Arduino-ESP32 support files is found here: 

NOTE: You may already have SD and FS libraries on your PC located in:

1) C:\Program Files (x86)\Arduino\libraries

2) C:\Users\Your_Name\AppData\Local\Arduino15\libraries

3) C:\Users\Your_Name\Documents\Arduino\libraries

Personally, I moved them to private folders, zipped them up and moved them away from the Arduino IDE. This way only the ESP32 drivers will be used.

Some of the code related to displaying the date and time has been cleaned up so the line numbers in BME280_OLED_RGB_SNTP_SD.ino won't be the same as our earlier file, BME280_OLED_RGB_SNTP.ino .

Code changes for the SD drive are listed below:

- Lines 22 to 25 define the SD drivers and file system drivers needed to run the micro SD card drive

- Lines 106 to 115 start the SD drive with the ESP32 DevKit-C v4 specific pins

- Lines 290 to 304 contains a list of the File System calls for the SD drive. The calls or functions follow.

- In loop() most of the code is the same but line 258 contains the data as a numerical string, e.g., 2024.09.07,16:01:02. This will make it easier to log the temperature/humidity/BP on the SD drive

String Formatting (BME280_OLED_RGB_SNTP_SD.ino )

This was the first time I have worked with formatting time to be used as a string that could be written as a line of data to an SD drive.

The line numbers involved in the procedure start with line 215 in the function Line5SD().

I used http://gemini.google.com/app to get hints on how to manipulate time data to a character string. I listed the two web links on line 225.

The comments that follow the code should hopefully be helpful.

Here is an example of it working on the Serial Monitor.

The micro SD drive is now tested.