en:i2c
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en:i2c [2013/11/27 12:35] – created kaklik | en:i2c [2014/12/21 10:12] – completion fluktuacia | ||
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- | ====== I2C in MLAB system ====== | + | FIXME **This page is not fully translated, yet. Please help completing the translation.**\\ //(remove this paragraph once the translation is finished)// |
- | ===== Activating The I2C Port ===== | + | ====== I²C bus as an MLAB's component ====== |
+ | [[http:// | ||
+ | |||
+ | Thanks to an advancement in computer technologies [[en: | ||
- | The I2C port needs to be enabled in kernel before you can use it. This can be achieved by | + | ===== Linking of I²C devices ===== |
- | sudo modprobe i2c-dev | + | Although the I²C bus was originally designed to link devices on small scales (within the dimensions of PCB), using certain techniques it is possible to enlarge its range to tens of meters (( [[http:// |
- | + | ||
- | Then I²C bus interfaces | + | |
- | sudo i2cdetect -l | + | Linking of I²C devices within MLAB is implemented on several levels according to extent of a network. Locally (on scale of several meters), the modules are connected by MLAB cables and separated by [[en: |
- | ===== Checking For Connected Devices ===== | + | Over more extensive distances the bus is linked through shielded signal cables ending in female connectors and connected to [[en: |
- | At the command prompt type one of these depending on whether you are using the I2C-X port: | + | In the case of extensive networks I²C is replaced by other physical layer (CAN, Ethernet) that interconnects individual I²C network segments. |
- | sudo i2cdetect -y X | ||
- | The 7 bit I2C address of all found devices will be shown (ignoring the R/W bit, so I2C address 0000 0110 is displayed as hex 03). | ||
+ | ==== Pymlab package ==== | ||
+ | |||
+ | Pymlab represents a software package that enables a creation of network made of I²C devices and modules, which serve as routing points. It defines the structure of a network and addresses of individual nodes in a source file of a control program. Individual points in the network can than be accessed using simple python commands. | ||
- | ===== SMBus (System Management Bus) Functions ===== | + | The installation of the [[en: |
+ | |||
+ | sudo pip install pymlab | ||
- | SMBus (System Management Bus) is a subset from the I2C protocol | + | In case of having some older version of pymlab already installed, it is enough |
- | When writing a driver for an I2C device try to use the SMBus commands only (if it possible). It makes possible | + | |
- | Note address is the 7 bit address excluding the read / write bit (it will be shifted left 1 bit whne added to the read/write bit) | + | sudo pip install --upgrade pymlab |
- | long write_quick(int addr) | + | Both commands are equivalent and use the python package manager that contains [[https:// |
+ | This procedure should also download other packages used by pymlab such as cython-hidapi | ||
- | Send only the read / write bit | + | sudo apt-get install libudev-dev libusb-1.0-0-dev libhidapi-dev python-setuptools python-smbus cython |
- | long read_byte(int addr) | + | ===== Convertors to connect I²C to PC ===== |
- | Read a single byte from a device, without specifying a device register. | + | Although I²C is quite popular bus suitable to connect different sensors over short distances, it is not usually found and readily available on regular computers with exception of [[http:// |
+ | ==== USB interface ==== | ||
- | long write_byte(int addr,char val) | + | Proprietary designs: |
- | Send a single byte to a device | + | * [[http:// |
+ | * [[http:// | ||
+ | * [[http:// | ||
+ | These share a common problem with a quality of drivers. Furthermore, | ||
- | long read_byte_data(int addr,char cmd) | ||
- | Read Byte Data transaction. | + | ==== USB HID ==== |
+ | For connections without the need for drivers designed for specific hardware [[http:// | ||
- | long write_byte_data(int addr,char cmd,char val) | ||
- | Write Byte Data transaction. | + | ==== UART/RS232 to I²C ==== |
+ | NXP manufactures [[http:// | ||
- | long read_word_data(int addr,char cmd) | + | ==== Ethernet to I²C ==== |
- | Read Word Data transaction. | + | This type of convertor can be constructed using [[cs: |
+ | ===== I²C implementation in Linux systems ===== | ||
- | long write_word_data(int addr,char cmd,int val) | + | There exists a package of tools for working with I²C bus for Ubuntu that can be installed through: |
+ | sudo apt-get install i2c-tools | ||
- | Write Word Data transaction. | + | Due to the usual absence of //i2c-dev// (([[https:// |
+ | sudo modprobe i2c-dev | ||
+ | <WRAP tip> | ||
+ | Modprobe command adds the module only to the kernel instance that is already running. Therefore, after reboot, the module will probably still be missing. If we do not want to use modprobe command on next computer start, we need to add following line to / | ||
+ | i2c-dev | ||
+ | </ | ||
- | long process_call(int addr,char cmd,int val) | + | It is now possible to list available I²C buses: |
- | Process Call transaction. | + | $ sudo i2cdetect -l |
+ | i2c-0 i2c | ||
+ | i2c-1 i2c | ||
+ | i2c-2 i2c | ||
+ | i2c-3 i2c | ||
+ | i2c-4 i2c | ||
+ | i2c-5 i2c | ||
+ | i2c-6 i2c | ||
+ | Using // | ||
- | long[] read_block_data(int addr,char cmd) | + | kaklik@radio-arm-0: |
+ | | ||
+ | 00: -- -- -- -- -- -- -- -- -- -- -- -- -- | ||
+ | 10: UU -- -- -- -- -- -- -- -- -- -- -- -- -- 1e -- | ||
+ | 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- | ||
+ | 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- | ||
+ | 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- | ||
+ | 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- | ||
+ | 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- | ||
+ | 70: 70 -- -- -- -- -- -- -- | ||
+ | kaklik@radio-arm-0: | ||
- | Read Block Data transaction. | + | The output above shows, that apart from system device with 0x10 address, there are to additional devices connected to the bus: 0x1e ([[cs: |
+ | ==== Communication with I²C devices ==== | ||
- | write_block_data(int addr,char cmd,long vals[]) | + | The bus can be controlled either by using system kernel interface or a service utility that is a part of i2c-tools package: |
- | Write up to 32 bytes to a device. | + | $ apropos i2c |
+ | i2cdetect (8) - detect I2C chips | ||
+ | i2cdump (8) - examine I2C registers | ||
+ | i2cget (8) - read from I2C/SMBus chip registers | ||
+ | i2cset (8) - set I2C registers | ||
+ | === Writing === | ||
- | long[] block_process_call(int addr,char cmd,long vals[]) | + | Writing is executed by i2cset command. A following |
- | Block Process Call transaction. | + | ~$ sudo i2cset -y -r 1 0x70 0xff |
- | I2C Access Functions | + | Value 0xff written, readback matched |
+ | The command triggers all I²C channels on I²CHub ((caution is necessary as having the same addresses on several channels or devices will cause a collision and locking of the bus. In this event the bus has to be reset by disconnecting the power supply or through RESET pin on I2CHUB module)). | ||
- | long[] read_i2c_block_data(int addr,char cmd) | + | === Reading === |
- | Block Read transaction. | + | Reading from I²CHub is atypical as well, because the data registry is not addressed: |
+ | :~$ sudo i2cget -y 1 0x70 | ||
+ | 0xff | ||
- | write_i2c_block_data(int addr,char cmd,long vals[]) | ||
- | Block Write transaction. | + | ===== Other operating systems ===== |
+ | On other OS (like Windows or Mac OS), where we cannot or do not want to use kernel I²C interface support, we may use Python programming environment that is multi-platform. | ||
- | ===== References | + | ===== Related sites ===== |
- | * [[http:// | + | * [[cs: |
- | * [[http:// | + | * [[cs:i2c-pic-usb|I2C-PIC-USB]] - Konvertor I²C na USB s PIC |
+ | * [[cs: | ||
+ | * [[cs:arm|Procesory architektury ARM ve stavebnici MLAB]] | ||
+ | * [[cs:odroid-x2]] | ||
+ | * [[cs: | ||
+ | * [[cs: | ||
+ | * [[cs:pymlab]] |
en/i2c.txt · Last modified: 2014/12/21 10:42 (external edit)