Page 125 - Toucpad robotics C11

Data Framing: Data is transmitted in packets called “frames.” Each frame typically includes:
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∑ A start bit (signals the beginning of data).
∑ Data bits (usually 5 to 9 bits, representing the actual data).
∑ An optional parity bit (for basic error checking).
∑ One or more stop bits (signals the end of data).
Uses in Robotics

Microcontroller to PC Communication: Often used for debugging, sending log data from a robot’s microcontroller
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to a computer’s serial port.
Interfacing with Modules: Connecting microcontrollers to various modules like Global Positioning System (GPS)
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receivers, Bluetooth modules, Wi-Fi modules, or Radio Frequency Identification (RFID) readers.
Simple Sensor Communication: For sensors that only need to send data periodically and don’t require high speed
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or complex networking.

Speed and Performance
Lower Speed: Generally the slowest among the protocols discussed here. Typical maximum baud rates range from
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9600 bits per second up to around 1 Megabit per second (Mbps).
Limitations: Speed is limited by the accuracy of the internal clocks of the communicating devices. A significant
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difference in baud rate can lead to corrupted data.
Error Detection and Reliability
Basic Error Detection: Can include an optional parity bit for simple error checking. The parity bit indicates
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whether the number of ‘1’ bits in the data frame is even or odd. If the receiver calculates a different parity, it knows
an error occurred.
No Automatic Retransmission: UART itself does not have mechanisms for automatic error correction or retransmission
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of corrupted data. This must be handled by higher-level software.
Reliability: Generally reliable for short-distance, low-speed communication between two devices.
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Inter-Integrated Circuit (I2C)
Description
Inter-Integrated Circuit, often pronounced “I-squared-C” or “I-two-C,” is a synchronous, multi-master, multi-slave serial
communication protocol developed by Philips (now NXP Semiconductors). “Synchronous” means it uses a shared clock
line for synchronization.

Key Characteristics and Differences
Synchronous: Uses a common clock signal for synchronization.
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Two Wires: Requires only two bidirectional wires:
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∑ Serial Data Line (SDA): For transmitting and receiving data.
∑ Serial Clock Line (SCL): For providing the clock signal.
Multi-Master, Multi-Slave: Allows multiple “master” devices (which control the communication) and multiple
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“slave” devices (which respond to commands) to share the same two bus lines.
Addressing: Each slave device on the I2C bus has a unique 7-bit (or sometimes 10-bit) address. The master addresses
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a specific slave by sending its address, allowing it to communicate with individual devices on the shared bus.
Acknowledgement (ACK) Mechanism: After each byte of data is transferred, the receiving device sends an
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acknowledgement signal, confirming successful receipt. This improves reliability.
Pull-up Resistors: Requires external pull-up resistors on both the Serial Data Line and Serial Clock Line wires to
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function correctly.

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Electrical and Control Systems