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Diffstat (limited to 'docs/source/i2c.rst')
| -rw-r--r-- | docs/source/i2c.rst | 54 |
1 files changed, 18 insertions, 36 deletions
diff --git a/docs/source/i2c.rst b/docs/source/i2c.rst index b4a996b..e3d68c0 100644 --- a/docs/source/i2c.rst +++ b/docs/source/i2c.rst @@ -1,15 +1,8 @@ .. _i2c: -===== |i2c| ===== -.. note:: - - The |i2c| interface is currently only available from the 'i2c' branch - of the github `libmaple <http://github.com/leaflabs/libmaple>`_ - repository. - |i2c| is a crude and easy-to-hack serial protocol that requires only two wires/channels for communication between many devices. Every message passed on the bus is between a *master* (who initiates the @@ -22,7 +15,7 @@ value, is achieved by writing to set the memory location then reading to pull out the data. Note that the master/slave designation is on a message-by-message -basis. The Maple can act as both a master (messages initiated by user +basis. Maple can act as both a master (messages initiated by user code) and slave device (responding to requests via configurable interrupt handlers) at the same time. @@ -32,15 +25,15 @@ interrupt handlers) at the same time. Hardware/Circuit Design ----------------------- -The Maple has two |i2c| ports. Port 1 (i2c1) has SDA on header D9 and -SCL on D5; Port 2 (i2c2) has SDA on D30 and SCL on D29. +.. FIXME [0.0.10 add links to board-specific values] -The Maple reliably communicates with up to a 400kHz clock speed; this -doesn't translate into a 400kbps data rate except in extreme cases -because of addressing and protocol overhead. We have tested clock -speeds up to a megahertz and have had mixed results; in theory it -could be possible to achieve even higher rates, but signal quality -degrades rapidly and the bus becomes unreliable. +Maple boards have two |i2c| ports. Maples reliably communicate with +up to a 400kHz clock speed; this doesn't translate into a 400kbps data +rate except in extreme cases because of addressing and protocol +overhead. We have tested clock speeds up to a megahertz and have had +mixed results; in theory it could be possible to achieve even higher +rates, but signal quality degrades rapidly, and the bus becomes +unreliable. Proper wiring and pull-up resistor selection are essential when incorporating |i2c| into a circuit, especially with data rates above @@ -55,33 +48,22 @@ oscilloscope to debug any issues. Function Reference ------------------ -The function API for |i2c| is not finished! See the `source code -<http://github.com/leaflabs/libmaple/blob/i2c/libmaple/i2c.h>`_ for -now. - -.. TODO link to libmaple I2C docs once (1) finished, (2) in master +Currently, only low-level support in :ref:`libmaple-i2c` exists. A +Wiring-style library is planned for a future release. SMBus ----- -The STM32 microcontroller has hardware support for SMBus; we simply -have not written software for it. The SMBAL line for i2c1 is on header -D4 and for i2c2 is on D31. - -.. TODO link to libmaple SMBus docs once (1) finished, (2) in master +The STM32 microcontroller has hardware support for SMBus, but software +for it is not yet implemented. .. _i2c-recommended-reading: Recommended Reading ------------------- -* `i2c-bus.org <http://www.i2c-bus.org/>`_ -* `Wikipedia Article on i2c <http://en.wikipedia.org/wiki/I%C2%B2C>`_ -* `Arduino i2c/TWI reference <http://www.arduino.cc/playground/Learning/I2C>`_ -* STMicro documentation for STM32F103RB microcontroller: - - * `Datasheet <http://www.st.com/stonline/products/literature/ds/13587.pdf>`_ (pdf) - * `Reference Manual <http://www.st.com/stonline/products/literature/rm/13902.pdf>`_ (pdf) - * `Application Note on Advanced I2C Usage - <http://www.st.com/stonline/products/literature/an/15021.pdf>`_ - (pdf) +* `I2C Bus <http://www.i2c-bus.org/>`_ +* `Wikipedia: I2C <http://en.wikipedia.org/wiki/I%C2%B2C>`_ +* `Arduino I2C/TWI reference <http://www.arduino.cc/playground/Learning/I2C>`_ +* ST `Application Note on Advanced I2C Usage + <http://www.st.com/stonline/products/literature/an/15021.pdf>`_ (PDF) |