Resource Note - Digital Serial Bus Technologies - I2C

In a context of digital electronics, a brief couple of resources bout the I²C serial bus protocol:

• Intefacing with the Linux kernel
• i2c-tools - I²C Tools for Linux
• libsoc
• Generic kernel interfaces
• ioctls
• Does not depend on i2c-tools
• See also 
• Benchoff, Brian.Speeding Up BeagleBone Black GPIO A Thousand Times. 2013
  
• Direct I/O onto /dev/mem to enable the SPI0 module clock, prior to GPIO I/O

• Blozis, Steve and Jean-Marc Irazaba. I²C Logic Family Overview . Philips. 2004
• Extensive presentation, even in its "slide format"
• Provides a thorough technical overview about I²C as a serial bus protocol
• Contains some useful "Best practice" advice, e.g. with a reference to the NXP P82B96 Dual bidirectional bus buffer

  

•  Blozis, Steve and Jean-Marc Irazaba. I²C Manual. Philips. 2003
• Provides an overview and comparison onto other serial bus protocols
• UART
• SPI
• CAN
• USB
• IEEE-1394 Firewire
• SMBUS
• A survey of individual connectors for cables in circuits using those protocols is available from Western Digital: WD Interface Guide (HTML)  (PDF)
•  Thorough explanation of theory and technology represented in the I²C serial bus protocol
• Observe that the I²C serial bus, in bidirectional bus operation, may be operated at one of three individual rates of clock timing -- maximum clock rates:
• 100 kbit/s (Standard-mode / Sm)
• 400 kbit/s (Fast-mode / Fm)
• 1 Mbit/s (Fast-mode Plus / Fm+
• 3.4 Mbit/s (High-speed mode / Hs-mode)
• In unidirectional bus operation, the bus may be operated in Ultra Fast-mode (UFm) at a maximum clock rate of 5 Mbit/s
• A multi-master I²C  protocol, effectively, would require a bidirectional mode of I²C bus operation

• Topic: Using I²C functions on contemporary single board computer platforms
• I²C on Raspberry Pi (RPi)
• Magda, Yury. Raspberry Pi Measurement Electronics: hardware and software. Second edition (Kindle). 2014
• uses i2c-tools (see previous items)
• Note that the RPi uses a Broadcom BCM2835 as a microcontroller munit (MCU). 
• Lacking further documentation about the I²C  interface(s) on the BCM2835 , the lack of availability of the BCM2835 data sheet may effectively serve to limit any I²C development on the RPi
• See also: Discussion in RPi forums
• Alternately: The BCM2835  may be found to publish interfaces for SPI and USB 2, as made avaialble via the RPi board. USB in particular is used on the RPi board.
•  I²C on the BeagleBone Black (BBB)
• PRU-ICSS modules on the TI Sitara MCU (ie. TI AM3358)
• See also: BBB - Working with the PRU-ICSS/PRUSSv2, Element 14 Community 
• Note: PRU-ICSS may be capable of only Standard-mode (100k) or Fast-mode (400k) I2C. See  Technical Reference Manual (AM335x) p. 4484 noting the specification of 100k or 400k
• Block view: Two PRU-ICSS modules in each TI Sitara MCU; One TI Sitara MCU to on each BBB. 
• See also: 
• System Refertence Manual (SRM) for BeagleBone Black. CircuitCo
• AM3358 Technical Documents. Texas Instruments.
• Data sheet for AM3358 
• Pinmux utility
• User Guide (AM335x) 13 pp.
• Note the section about interrupt events, including "INT_STS2_REG.GPIO_R/F_IT"
• Technical Reference Manual (AM335x) 1566 pp.
• Note specifically, sublcause 9 of the manual, Control Module through to subclause 9.2.2.1, Mode selection, concerning the two-bit MUXMODE field and its specifier values
• Note also subclause 4 of the manual, which is dedicated to the PRU-ICSS
• Note, thirdly, subclause 21.3.15 of the manual, How to Program I2C - using the PRU-ICSS function set
• For I²C development with the BBB and other TI Sitara (AM335x) platforms, it may be feasible to use the I²C features of one or both of the PRU-ICSS modules on the AM335x device, rather than reconfiguring the pimux of the primary ARM(R) Cortex A8 MCU via SYSBOOT
• References onto broader theory
• Bosworth, Edward L.  Introduction to Computer Organization (CPSC 2105). 2012
• Knight, Thomas, et al. CADR (MIT AI Memo 528)
• PRU-ICSS. Texas Instruments
• Hardware information (individual microcontrollers' product pages)
• Software information
• Getting Started Guide (PRU-ICSS)
• Recommends software packages for the development environment
• Code Composer Studio (CCS) v6
• See also: CCS for Sitara ARM
• NON-FREE (cf. DFSG)
• PRU Code Generation Tools (add-on, might be available via CCS UI)
•  PRU-SWPKG (see subsequent items) 
• Header files (PRU-ICSS) 
• PRU-ICSS Remoteproc Driver (Linux) (e.g LinuxLink RTOS on BBB)
• PRU-ICSS Rpmsg Driver (Linux) (e.g LinuxLink RTOS on BBB)
• See also: Linux EZ Software Devleopment Kit (EZSDK) for Sitara(tm) Processors . Texas Instruments
• NON-FREE (DFSG)  - Based on Code Composer Studio (CCS)
• Programmable Realtime Unit Software Development. Texas Instruments
• PRU Assembly Reference Guide
• PRU Assembly Instructions
• Notice the "Wait until bit set" and "Wait until clear" functions, each available for polling a status bit in a PRU register
• Advanced PRU Assembly Topics
• Debugging PRU Assembly Code
• PASM Tool
• PRU Linux Loader 
• Usage: Load assembler program into independent PRU memory area
• cf. PRU-ICSS Remoteproc driver (load time); see also: Rpmsg driver (runtime)
• See also: app_loader source code, beagleboard community
• PRU Software Support Package
• Specifically, the PRU-SWPKG edition (actively maintained) (x86 32 bit. For advice about installing 32 bit support on amd64 Ubuntu, see advisory note)
• PRU-SWPKG [Tools Platform]
• Depends on Code Composer Studio (CCS) [Tools Platform] a non-free component (cf. DFSG)
• PASM [Toolchain Component]
• FOSS (DFSG Compliant)
•  PASM (AM335X PRU) Source code available via beagleboard community at GitHub
• See also: LinuxLink embedded Linux Development Center for TI AM335x Sitara [Tools Platform, RootFS, Kernel]
• compatibility onto PASM - ?
• one of GNU libc / uClibc [compiler toolchain]
• Alternately, see also: Linaro Toolchain (BBB) (cf. TI EZSDK)
• A single PRU-ICSS module may provide access to an I²C bus, across the full range of available rates of clock timing in the I²C specification
• Driver support
• Integrating the PRU-ICSS within userspace software : ?
• Patching i2c-tools ? libsoc ?
• Integrating the PRU-ICSS within kernel drivers: 
• Module uio_pruss and BBB device tree updates
• See also, previous items (Remoteproc, Rpmsg drivers )
• Sitara Linux SDK
• Availability (???) see Linux EZ Software Devleopment Kit (EZSDK) for Sitara(tm) Processors  (???)  
• Refer to Release notes in ... ??? PRU-SWPKG ???
• ??? AM335x SDK BSP Source Code (???) 
• See also: BeagleBone PRU Notes, Embedded Linux WIki
• Accessing the  I2C interfaces (three available?) on the primary TI Sitara MCU module
• See also: BBB SRM
• Processor mode switching, Pinmux configuration
• uBoot
• Microinstructions for processor mode switch?
• SYSBOOT 
• See also: BeagleBone I2C2 Enable, Embedded Linux Wiki
• See also: Notes onto RTOS Linux, DSP42.
• Specifically, Timesys LinuxLink provides direct support for LinuxLink RTOS on the BeagleBone Black platform. Links and more are available at the other article