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esp-idf/examples/peripherals/i2c/i2c_self_test/README.md

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I2C Self-Test Example

(See the README.md file in the upper level 'examples' directory for more information about examples.)

Overview

This example demonstrates basic usage of I2C driver by running two tasks on I2C bus:

  1. Read external I2C sensor, here we take the BH1750 ambient light sensor (GY-30 module) for an example.
  2. Use one of ESP32’s I2C port (master mode) to read and write another I2C port (slave mode) in ESP32.

If you have a new I2C application to go (for example, read the temperature data from external sensor with I2C interface), try this as a basic template, then add your own code.

How to use example

Hardware Required

To run this example, you should have one ESP32 dev board (e.g. ESP32-WROVER Kit) or ESP32 core board (e.g. ESP32-DevKitC). Optionally, you can also connect an external sensor, here we choose the BH1750 just for an example. BH1750 is a digital ambient light sensor, for more information about it, you can read the PDF of this sensor.

Pin Assignment:

Note: The following pin assignments are used by default, yout can change these in the menuconfig .

SDA SCL
ESP32 I2C Master GPIO18 GPIO19
ESP32 I2C Slave GPIO25 GPIO26
BH1750 Sensor SDA SCL

  • slave:

    • GPIO25 is assigned as the data signal of I2C slave port
    • GPIO26 is assigned as the clock signal of I2C slave port

  • master:

    • GPIO18 is assigned as the data signal of I2C master port
    • GPIO19 is assigned as the clock signal of I2C master port

  • Connection:

    • connect GPIO18 with GPIO25
    • connect GPIO19 with GPIO26
    • connect SDA/SCL of BH1750 sensor with GPIO18/GPIO19

**Note: ** There’s no need to add an external pull-up resistors for SDA/SCL pin, because the driver will enable the internal pull-up resistors.

Configure the project

Open the project configuration menu (idf.py menuconfig). Then go into Example Configuration menu.

  • In the I2C Master submenu, you can set the pin number of SDA/SCL according to your board. Also you can modify the I2C port number and freauency of the master.
  • In the I2C Slave submenu, you can set the pin number of SDA/SCL according to your board. Also you can modify the I2C port number and address of the slave.
  • In the BH1750 Sensor submenu, you can choose the slave address of BH1750 accroding to the pin level of ADDR pin (if the pin level of ADDR is low then the address is 0x23, otherwise it is 0x5c). Here you can also control the operation mode of BH1750, each mode has a different resolution and measurement time. For example, in the One Time L-Resolution mode, the resolution is 4 Lux and measurement time is typically 16ms (higher resolution means longer measurement time). For more information, you can consult the datasheet of BH1750.

Build and Flash

Enter idf.py -p PORT flash monitor to build, flash and monitor the project.

(To exit the serial monitor, type Ctrl-].)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

Example Output

I (6495) i2c-example: TASK[1] test cnt: 1
*******************
TASK[1]  MASTER READ SENSOR( BH1750 )
*******************
data_h: 01
data_l: d0
sensor val: 386.67 [Lux]
I (6695) i2c-example: TASK[0] test cnt: 2
*******************
TASK[0]  MASTER READ SENSOR( BH1750 )
*******************
data_h: 01
data_l: d0
sensor val: 386.67 [Lux]
*******************
TASK[0]  MASTER READ FROM SLAVE
*******************
====TASK[0] Slave buffer data ====
00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 
20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 
30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f 
40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f 
50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f 
60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f 
70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f 

====TASK[0] Master read ====
00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 
20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 
30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f 
40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f 
50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f 
60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f 
70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f 

*******************
TASK[1]  MASTER READ FROM SLAVE
*******************
====TASK[1] Slave buffer data ====
00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 
20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 
30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f 
40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f 
50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f 
60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f 
70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f 

====TASK[1] Master read ====
00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 
10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 
20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 
30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f 
40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f 
50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f 
60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f 
70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f 

*******************
TASK[0]  MASTER WRITE TO SLAVE
*******************
----TASK[0] Master write ----
0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 18 19 
1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27 28 29 
2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 36 37 38 39 
3a 3b 3c 3d 3e 3f 40 41 42 43 44 45 46 47 48 49 
4a 4b 4c 4d 4e 4f 50 51 52 53 54 55 56 57 58 59 
5a 5b 5c 5d 5e 5f 60 61 62 63 64 65 66 67 68 69 
6a 6b 6c 6d 6e 6f 70 71 72 73 74 75 76 77 78 79 
7a 7b 7c 7d 7e 7f 80 81 82 83 84 85 86 87 88 89 

----TASK[0] Slave read: [128] bytes ----
0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 18 19 
1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27 28 29 
2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 36 37 38 39 
3a 3b 3c 3d 3e 3f 40 41 42 43 44 45 46 47 48 49 
4a 4b 4c 4d 4e 4f 50 51 52 53 54 55 56 57 58 59 
5a 5b 5c 5d 5e 5f 60 61 62 63 64 65 66 67 68 69 
6a 6b 6c 6d 6e 6f 70 71 72 73 74 75 76 77 78 79 
7a 7b 7c 7d 7e 7f 80 81 82 83 84 85 86 87 88 89

Troubleshooting

  • BH1750 has two I2C address, which is decided by the voltage level of ADDR pin at start up. Make sure to check your schemetic before run this example.

(For any technical queries, please open an issue on GitHub. We will get back to you as soon as possible.)