Editing Multi-purpose Embedded System

==Hardware Architecture==
[[Image:Mpes hw archi.png]]

===MCU===
*MCU can be 8-bit/16-bit/32-bit
*MCU should have sufficient RAM (i.e. no external RAM required)
*MCU should have program Flash (i.e. no external program flash required)


===Data Memory===
*Use serial bus (I2C/SPI) to expand data memory to save I/O pins
*Need a file system to access the data
*EEPROM for small block of re-writable data
*Flash for large block of re-writable data


===Communication===
*RS232 for short distance communication with PC
*RS485 for longer distance communication (upto 1200m) over a set of devices
*USB for USB communication with PC
*Ethernet for Internet connectivity
**Use of Ethernet controller (e.g. [http://www.davicom.com.tw/userfile/24247/DM9000A-DS-F01-101906.pdf DM9000A] (requiring software TCP/IP stack)
**User of TCP/IP chip (e.g. [http://www.wiznet.co.kr/ W5300])
*GPIB for automated test equipment


===User Interface===
*Graphical displays (LCD, VFD, etc.)
*Keypad for input


===Sensory Control===
*ADC for analog feedback signals
**Requires anti-aliasing analog filters and op-amp circuits
***Use desktop software (e.g. [http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en010007 FilterLab]) to design circuits
**May incorporate [http://www-users.cs.york.ac.uk/~fisher/mkfilter/ digital filter] to improve reduce noise
*DAC for analog control signals
**Refer to [http://www.opencircuits.com/Modulation_Plugin here] if modulation is needed.
*GPIO for digital feedback and control signals
**Option 1: directly controlled by MCU
**Option 2: indirectly through D-type flip-flops (e.g. [http://www.datasheetcatalog.org/datasheet/philips/74lv574.pdf 74LV154]) for low pin counts MCU
**Option 3: indirectly through shift register flip-flops (e.g. [http://www.datasheetcatalog.com/datasheets_pdf/M/7/4/H/M74HC165.shtml 74HC165] for input, [http://www.datasheetcatalog.org/datasheet/texasinstruments/tpic6595.pdf TPIC6595] or [http://www.datasheetcatalog.org/datasheet/philips/74HC_HCT595_CNV_3.pdf 74HC595] for output ) for extremely low pin count MCU


==Software Architecture==

===RTOS===
                +-----------+-----------+----------------------------------------------+
  Application   |  Task 1   |  Task 2   |    ...                                       |
                +-----------+-----------+------------+----------------------+----------+
  Standard API  |          POSIX System Call         |     POSIX Thread     |  C-Lib   |
                +------------------+-----------------+----------------------+----------+
    Kernel      | Power Management |                 |    Task Scheduler    |
                +------------------+                 +----------+-----------+ 
                |               Drivers              | FreeRTOS | Coroutine |
                +------+-----+-----+-----+-----+-----+----------+-----------+
    Hardware    | UART | ADC | DAC | NVM | PWM | ... |  TIMERS  | 
                +------+-----+-----+-----+-----+-----+----------+
*The task scheduler is based on [http://www.freertos.org/ FreeRTOS] incorporating coroutine developed by [http://www.chiark.greenend.org.uk/~sgtatham/coroutines.html Simon Tatham]. The scheduler API is wrapped by the [http://www.die.net/doc/linux/man/man2/ POSIX] Thread API.
**e.g. pthread_create(), usleep(), etc.
*Software drivers are developed to allow users at Application Level to use the hardware (e.g. ADC, DAC, UART, NVM etc) through the [http://www.die.net/doc/linux/man/man2/ POSIX] System call API.
**e.g. open(), write(), read(), ioctl(), lseek(), etc.
*The most up-to-date development can be found at repository [http://chungyan5.no-ip.org/vc/?root=freertos_posix freertos_posix]


===GUI===
                       +---------------+----------------+
  User Applications    | Application 1 | Application 2  |
                       |               +----------------+------------------+
    Middlewares        |               |    Toolkits    |  Window Manager  |
                       +---------------+----------------+------------------+
    GUI Library        |            Graphics Engine (inc Font)             |
                       +-----------+----------------------+----------------+
    POSIX API          |           |  POSIX System Calls  | POSIX Threads  |
                       |           +-----------+----------+----------------+
  Drivers & Scheduler  |  Display  |  Pointer  |  Keypad  | Task Scheduler |
                       +-----------+-----------+----------+----------------+


===TCP/IP Stack===
                   +---------------------------------------------+--------------------+-------+
  Applications     |            Ethernet Application             |  GUI Application   |  ...  |
                   +--------+------+------+----------+------+----+                    |       |
  Web Libraries    |  Web   | DHCP | SNMP |   DNS    | SMTP |... |                    |       |
                   | Server |      |      | Resolver |      |    |                    |       |
                   +--------+------+------+----------+------+----+                    |       |
  Socket API       |            Linux Socket Wrapper             |                    |       |
                   |          +----------------------------------+                    |       |
  TCP/IP Stack     |          |               uip                |                    |       |
                   |          +----------------------------------+                    |       |
                   |          |       Ethernet Thread            |                    |       |
                   |          +---------------------------+------+--------------------+-------+
  POSIX API        |          |    POSIX System Calls     |            POSIX Threads          |
                   +----------+---------------------------+-----------------------------------+
                   |               Drivers                |            Task Scheduler         |
                   +----------+---------------------------+-----------------------------------+
                   |   H/W    |
                   |  TCP/IP  |
                   |  Stack   |
                   +----------+
*See [http://www.opencircuits.com/Ethernet_Module here] for description


===File System===
                  +------------+------------+------------+------------+------------+------------+
 Application      |   App 1    |   App 2    |   App 3    |   App 4    |   App 5    |   App 6    |
                  +------------+------+-----+------------+------------+------------+------------+
 Standard Lib     |  Stdio.h wrapper  |                  |                                      |
                  +-------------------+                  |                                      |
 File System      |      FatFs        |                  |            POSIX Threads             |
                  |          +--------+                  |                                      |
 POSIX API        |          |    POSIX System Calls     |                                      |
                  +----------+---------------------------+--------------------------------------+
                  |               Drivers                |            Task Scheduler            |
                  +--------------------------------------+--------------------------------------+

*[http://efsl.be/ Embedded Filesystem Library]
*[http://elm-chan.org/fsw/ff/00index_e.html FatFs]

===Remote Access===