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OVMS3-idf/examples/peripherals/i2c/i2c_tools/README.md

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I2C Tools Example

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

Overview

I2C Tools is a simple but very useful tool for developing I2C related applications, which is also famous in Linux platform. This example just implements some of basic features of I2C Tools based on esp32 console component. As follows, this example supports five command-line tools:

  1. i2cconfig: It will configure the I2C bus with specific GPIO number, port number and frequency.
  2. i2cdetect: It will scan an I2C bus for devices and output a table with the list of detected devices on the bus.
  3. i2cget: It will read registers visible through the I2C bus.
  4. i2cset: It will set registers visible through the I2C bus.
  5. i2cdump: It will examine registers visible through the I2C bus.

If you have some trouble in developing I2C related applications, or just want to test some functions of one I2C device, you can play with this example first.

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). For test purpose, you should have a kind of device with I2C interface as well. Here we will take the CCS811 sensor as an example to show how to test the function of this sensor without writing any code (just use the command-line tools supported by this example). For more information about CCS811, you can consult the online datasheet.

Pin Assignment:

Note: The following pin assignments are used by default, you can change them with i2cconfig command at any time.

SDA SCL GND Other VCC
ESP32 I2C Master GPIO18 GPIO19 GND GND 3.3V
Sensor SDA SCL GND WAK VCC

**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 itself.

Configure the project

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

  • You can choose whether or not to save command history into flash in Store command history in flash option.
  • You can set the maximum number of command line arguments under Maximum number of command line arguments option.
  • You can set the command line buffer length under Command line buffer length option.

Build and Flash

Run idf.py -p PORT flash monitor to build and flash 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

Check all supported commands and their usages

 ==============================================================
 |       Steps to Use i2c-tools on ESP32                      |
 |                                                            |
 |  1. Try 'help', check all supported commands               |
 |  2. Try 'i2cconfig' to configure your I2C bus              |
 |  3. Try 'i2cdetect' to scan devices on the bus             |
 |  4. Try 'i2cget' to get the content of specific register   |
 |  5. Try 'i2cset' to set the value of specific register     |
 |  6. Try 'i2cdump' to dump all the register (Experiment)    |
 |                                                            |
 ==============================================================

esp32> help
help 
  Print the list of registered commands

i2cconfig  [--port=<0|1>] [--freq=<Hz>] --sda=<gpio> --scl=<gpio>
  Config I2C bus
  --port=<0|1>  Set the I2C bus port number
   --freq=<Hz>  Set the frequency(Hz) of I2C bus
  --sda=<gpio>  Set the gpio for I2C SDA
  --scl=<gpio>  Set the gpio for I2C SCL

i2cdetect 
  Scan I2C bus for devices

i2cget  -c <chip_addr> [-r <register_addr>] [-l <length>]
  Read registers visible through the I2C bus
  -c, --chip=<chip_addr>  Specify the address of the chip on that bus
  -r, --register=<register_addr>  Specify the address on that chip to read from
  -l, --length=<length>  Specify the length to read from that data address

i2cset  -c <chip_addr> [-r <register_addr>] [<data>]...
  Set registers visible through the I2C bus
  -c, --chip=<chip_addr>  Specify the address of the chip on that bus
  -r, --register=<register_addr>  Specify the address on that chip to read from
        <data>  Specify the data to write to that data address

i2cdump  -c <chip_addr> [-s <size>]
  Examine registers visible through the I2C bus
  -c, --chip=<chip_addr>  Specify the address of the chip on that bus
  -s, --size=<size>  Specify the size of each read

free 
  Get the current size of free heap memory

heap 
  Get minimum size of free heap memory that was available during program execu
  tion

version 
  Get version of chip and SDK

restart 
  Software reset of the chip

deep_sleep  [-t <t>] [--io=<n>] [--io_level=<0|1>]
  Enter deep sleep mode. Two wakeup modes are supported: timer and GPIO. If no
  wakeup option is specified, will sleep indefinitely.
  -t, --time=<t>  Wake up time, ms
      --io=<n>  If specified, wakeup using GPIO with given number
  --io_level=<0|1>  GPIO level to trigger wakeup

light_sleep  [-t <t>] [--io=<n>]... [--io_level=<0|1>]...
  Enter light sleep mode. Two wakeup modes are supported: timer and GPIO. Mult
  iple GPIO pins can be specified using pairs of 'io' and 'io_level' arguments
  . Will also wake up on UART input.
  -t, --time=<t>  Wake up time, ms
      --io=<n>  If specified, wakeup using GPIO with given number
  --io_level=<0|1>  GPIO level to trigger wakeup

tasks 
  Get information about running tasks

Configure the I2C bus

esp32> i2cconfig --port=0 --sda=18 --scl=19 --freq=100000
  • --port option to specify the port of I2C, here we choose port 0 for test.
  • --sda and --scl options to specify the gpio number used by I2C bus, here we choose GPIO18 as the SDA and GPIO19 as the SCL.
  • --freq option to specify the frequency of I2C bus, here we set to 100KHz.

Check the I2C address (7 bits) on the I2C bus

esp32> i2cdetect
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- 5b -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
  • Here we found the address of CCS811 is 0x5b.

Get the value of status register

esp32> i2cget -c 0x5b -r 0x00 -l 1
0x10
  • -c option to specify the address of I2C device (acquired from i2cetect command).
  • -r option to specify the register address you want to inspect.
  • -l option to specify the length of the content.
  • Here the returned value 0x10 means that the sensor is just in the boot mode and is ready to go into application mode. For more information about CCS811 you should consult the official website.

Change the working mode

esp32> i2cset -c 0x5b -r 0xF4
I (734717) cmd_i2ctools: Write OK
esp32> i2cset -c 0x5b -r 0x01 0x10
I (1072047) cmd_i2ctools: Write OK
esp32> i2cget -c 0x5b -r 0x00 -l 1
0x98
  • Here we change the mode from boot to application and set a proper measure mode (by writing 0x10 to register 0x01)
  • Now the status value of the sensor is 0x98, which means a valid data is ready to read

Read the sensor data

esp32> i2cget -c 0x5b -r 0x02 -l 8
0x01 0xb0 0x00 0x04 0x98 0x00 0x19 0x8f
  • The register 0x02 will output 8 bytes result, mainly including value of eCO2、TVOC and there raw value. So the value of eCO2 is 0x01b0 ppm and value of TVOC is 0x04 ppb.

Troubleshooting

  • I don’t find any available address when running i2cdetect command.
    • Make sure your wiring connection is right.
    • Some sensor will have a “wake up” pin, via which user can put the sensor into a sleep mode. So make sure your sensor in not in the sleep state.
    • Reset you I2C device, and then run i2cdetect again.
  • I can’t get the right content when running i2cdump command.
    • Currently the i2cdump only support those who have the same content length of registers inside the I2C device. For example, if a device have three register addresses, and the content length at these address are 1 byte, 2 bytes and 4 bytes. In this case you should not expect this command to dump the register correctly.
  • I really input argument correctly, but the command line “discard” the last few arguements from time to time.
    • Enlarge the maximum number of arguments in the menuconfig.

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