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Thomas Fischl

• 1 Software
  • 1.1 Python library "pyI2C_MP_USB" (Windows, MacOS, Linux)
  • 1.2 Java library "jI2C_MP_USB" (Windows, MacOS, Linux)
  • 1.3 Kernel driver "i2c-tiny-usb" (Linux)
• 2 Firmware
  • 2.1 Source code and HEX file
  • 2.2 Firmware update via bootloader
• 3 Hardware
  • 3.1 Schematic - I2C-MP-USB's circuit diagram
  • 3.2 Partlist - Build your own I2C-MP-USB!
• 4 Troubleshooting
• 5 Gallery
• 6 Links

pyI2C_MP_USB is a Python library for the I2C-MP-USB adapter which allows easy, platform-independent access to I²C slaves. The API is mostly identical to the SMBus package, porting of the control source code to other hardware is therefore possible without much effort.

Installation

The easiest way to install the library is using pip:

pip install git+https://github.com/EmbedME/pyI2C_MP_USB

Drivers

The library uses libusb. On Linux and MacOS X no kernel driver is needed. Please use following tool for Windows to install the "WinUSB" driver:

Depending on the application, under Windows a libusb-1.0.dll is required. These can be found for various architectures on the libusb project homepage under "Download -> Windows Binaries". Please place the DLL in the application folder (e.g. in the "Scripts" folder for Anaconda Python).

Example

Write one byte to an EEPROM 24C02 at address 0x10; then read it back:

from i2c_mp_usb import I2C_MP_USB as SMBus
import time

bus = SMBus()
bus.write_byte_data(0x50, 0x10, 0xA5)   # Write byte to EEPROM
time.sleep(0.1)                         # Give EEPROM time to flash
data = bus.read_byte_data(0x50, 0x10)   # Read byte from EEPROM
print(data)

Throughput

A block read of 1000 bytes at 400kHz clock speed takes about 32ms on my test system (Ubuntu 16.04@ThinkPad X201). That means a transfer rate of 31.25 kBytes/s.

jI2C_MP_USB is a Java library which provides access to I2C slaves with an I2C-MP-USB adapter. It uses usb4java to talk over USB. Usb4java supports Linux (x86 32/64 bit, ARM 32/64 bit), OS X (x86 64 bit) and Windows (x86 32/64 bit).

Example

Read one byte from I²C device with address 0x50 from register address 0x10.

I2C_MP_USB i2c = new I2C_MP_USB();
i2c.connect();
i2c.setBaudrate(100);

byte test = i2c.readByteData(0x50, 0x10);
System.out.println(String.format("%02X", test));

i2c.disconnect();

For Linux there is an alternative to the library: The driver "i2c-tiny-usb" is part of the official Linux kernel and is included in most distributions. When the adapter is plugged in, it is automatically detected and registered:

$ dmesg | tail

usb 1-1.5.2.3: new full-speed USB device number 10 using ehci-pci
usb 1-1.5.2.3: New USB device found, idVendor=0403, idProduct=c631
usb 1-1.5.2.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-1.5.2.3: Product: I2C-MP-USB
usb 1-1.5.2.3: Manufacturer: www.fischl.de
usb 1-1.5.2.3: SerialNumber: 131E0000
i2c-tiny-usb 1-1.5.2.3:1.0: version 1.01 found at bus 001 address 010
i2c i2c-7: connected i2c-tiny-usb device
usbcore: registered new interface driver i2c-tiny-usb

Example using i2c-tools with an EEPROM 24C02 connected to the I2C-MP-USB.

1. Detect devices on the I²C bus:

   $ i2cdetect -y 7
        0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
   00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
   10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
   20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
   30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
   40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
   50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
   60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
   70: -- -- -- -- -- -- -- --

2. Write value 0x5A to EEPROM address 0x10:

   $ i2cset -y 7 0x50 0x10 0x5A

3. Read value from EEPROM address 0x10:

   $ i2cget -y 7 0x50 0x10
   0x5a

4. Dump EEPROM content at address range 0x00-0x1F:

   $ i2cdump -y -r 0x00-0x1F 7 0x50 b
        0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f    0123456789abcdef
   00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
   10: 5a ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    Z...............

Example using kernel module AT24 to access an EEPROM 24C02 connected to the I2C-MP-USB.

1. Load AT24 kernel module and register the EEPROM

   $ modprobe at24
   $ echo "24c02 0x50" > /sys/class/i2c-adapter/i2c-7/new_device

2. Dump the eeprom content

   $ hexdump -C /sys/bus/i2c/drivers/at24/7-0050/eeprom
   00000000  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
   00000010  5a ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |Z...............|
   00000020  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
   *
   00000100

3. Unregister the EEPROM

   $ echo "0x50" > /sys/class/i2c-adapter/i2c-7/delete_device

The firmware of I2C-MP-USB is available as precompiled HEX file and as C (XC8 compiler) source code.

Precompiled HEX and source code archive:

Start the bootloader via software (e.g. start_bootloader.py) or via hardware jumper: short JP1 and plug in I2C-MP-USB - now the bootloader starts. Use a bootloader application ( MPHidFlash) to load the new firmware into I2C-MP-USB:

mphidflash -w i2c_mp_usb_firmware_v1.0.hex

Here you find a list of all parts needed to build your own I2C-MP-USB board.

Partnumber	Value
C1, C2	4,7u
C3, C4	220n
IC1	PIC16F1455
IC2	MCP1700
LED1	blue LED
R1	270
R2, R3	4k7
X1	5pol 2.54mm
X2	USB-B

$ rmmod i2c-tiny-usb

$ echo $'blacklist i2c-tiny-usb\n' > /etc/modprobe.d/i2c.conf

sudo bash -c $'echo \'SUBSYSTEM=="usb", ATTRS{product}=="I2C-MP-USB", MODE="0666"\' > /etc/udev/rules.d/50-I2C_MP_USB.rules'
sudo udevadm control --reload-rules

$ modprobe mcp4018
$ echo "mcp4017-103 0x2f" > /sys/class/i2c-adapter/i2c-8/new_device
$ echo 12 > /sys/bus/i2c/drivers/mcp4018/8-002f/iio\:device0/out_resistance0_raw

$python3 smart_battery.py 
Temperature (°C):           20.850000000000023
Voltage (V):                11.986
Current (mA):               0
RelativeStateOfCharge (%):  92

$ python3 wsen_tids.py 
Temperature in °C:  18.23
Temperature in °C:  18.26
Temperature in °C:  18.24
Temperature in °C:  18.22

$ python3 wsen_hids.py 
Temperature: 17.63 °C, Humidity: 59.89 % 
Temperature: 17.63 °C, Humidity: 59.91 % 
Temperature: 17.65 °C, Humidity: 59.82 %

$ python3 wsen_pads.py 
Temperature: 20.01 °C, Pressure: 98.041 kPa 
Temperature: 20.01 °C, Pressure: 98.042 kPa 
Temperature: 20.01 °C, Pressure: 98.042 kPa

$ python3 ads1015.py 
Voltage: 2.229 V 
Voltage: 2.229 V