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Fixed typos in RS485 and made stuff clearer

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Sebastian 2015-05-20 22:42:51 +02:00
parent 3382ec240b
commit e559a72075
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README.md
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@ -9,12 +9,17 @@ The actual application layer will be developed independent of this specification
Physical Layer
--------------
The physical layer is based on a RS248 three wire bus (a differential pair for data and ground),
The physical layer is based on a RS485 three wire bus (a differential pair for data and ground),
using the *MCP2551* is used as transceiver chip.
Since this chip is actually a CAN-transceiver,
it has a well defined behaviour in case of collisions (no short circuits possible)
and it allows to read back the bits which were actually on the bus while sending.
This enables any device with a decent UART (microcontroller, raspi ...) to communicate over long distances (2000m+).
Additionally for most regular RS485 transceivers a collision on the bus results
in one transceiver pulling the bus while the other one pulls it high,
effectively creating a temporary short circuit.
Therefore using a CAN-transceiver is preferable for our bus configuration.
Using a sss7modem any device with a decent UART (microcontroller, raspi ...) can communicate over long distances (2000m+).
The data is send at 9600 Baud (aka. 9,6kbit/s) with a maximum baudrate error of +-5%,
to ensure that even the slowest microcontroller can participate in the communication.
A slow bitrate also necessary to keep communication and collision detection reliable over longer