MECH316 Mechatronics

Microprocessor

The brain of the mechatronic system as it processes the data and performs the calculations required to control the system

Arithemetic and Logic Unit (ALU)

In charge of performing mathematical and logic operations for the microproccesor.

Address Bus

Selects memory location to load data from or store data in.

Data Bus

Used to transport a word from or to the microprocesor and the memory.

Control Bus

Carries Clock Signals to sychronize other units in the microprocessor.

Special Function Registers

Used to control the microprocessor itself or to perform specific functions.

General Purpose Register

Memory locations available for the user inside of the microprocessor.

Control Unit

1. Controls timing and sequence of operations.

2. Generates clock for other components.

3. Fetches Loads from memory.

4. Executes instruction by controlling other units.

Coplex instruction Set Computing (CISC)

Each Instruction within the control unit can take different and several amount of clock cycles to compute.

Reduced Instruction Set Computing (RISC)

Every instruction withing the control unit takes a fixed amount of time.

Microcontroller

A single chip including CPU, memory, peripherals (digital and analogue)

Digital I/O

Data is binary, one pin controls one bit.

Analog I/O

Data is continious voltage between 0 and max.

Memory-mapped I/O

Data is mapped to special function registers. The address bus is used for both memory and peripherals. The code can access such data in the same way it accesses memory.

Port-Mapped I/O

A seperate bus connects Microprocessor with peripherals. Microproccesor must have dedicated instructions to access I/0 (Requires CISC)

Von Neumann Architecture

Data and instructions are stored in the same memory.

Harvard Architecture

Memory is split between Data Memory and Code Memory. It prevents memory corruption Issues.

Read-Only Memory (ROM)

Data is stored during maunfacturing proccess. Can not be wriiten by user.

Electrically Erasable Programmable Read Only Memory (EEPROM)

Can be written by special devices but not modified by code.

Random Access Memory (RAM)

Used to store temporary data, loses content when power removed.

SPI Protocol

Uses one master and one or more slaves

1. Master configures clock signal: frequency, polarity and phase

2. Master selects peripheral by acting SS=LOW

3. Data transfer can then commence

4. Master releases peripherals by bringing SS=HIGH

8 Specifications for mechatronic sensors

1. Range - Limits between which input can vary

2. Span - Max value-Min Value

3. Sensitivity - Output variation / Input Variation

4. Resolution - Smallest value of input variation

5. Nonlinearity error - Max error from linear output

6. Accuracy - Max extent to which measurement can be from the true value

7. Hysterisis - Max difference in output for increasing or decreasing input

8. Stability - Ability to give the same output when used to measure a constant input over a long time.

D/A Conversion

Input to conveter is a 8-bit binary word. The output voltage will be divided into 2^8 converters. A change of 1 bit is a change of output voltage = RANGE / 2^8. A simple d/a converter uses a summing amplifier.

A/D Conversion

A/D conversion, or analog-to-digital conversion, is the process of converting analog signals into digital form. It involves two main steps: sampling and quantization.

1. Sampling: The continuous analog signal is sampled at regular intervals. The amplitude of the analog signal is measured at each sampling point.

2. Quantization: The measured analog values are then quantized, meaning they are assigned a discrete digital value. This is done by dividing the range of possible analog values into a finite number of levels and assigning each sample to the closest level.

The digital values obtained through quantization are represented in binary form, typically using a fixed number of bits. The number of bits determines the resolution and accuracy of the digital representation.

Ramp Converters

A voltage is generated by a clock in steps and compared with the unknown analog input. When the comparator signals that the internally-generated voltage is grater than the input, then the value of the clock-counter is recorded as the corresponding digital value. It is easy to implement, however, it is quite slow and the time required for A/D conversion is not constant.

Succesive Approximation Converters

The A/D conversion always occur in a fixed number of steps, equal to the number of bits used for the conversion. The first step compares the MSB (worth half of the converter full scale VFS) with the unknown input. If the MSB is greater than the input then MSB=1, otherwise MSB=0. In the second step the value (MSB* VFS/2+ VFS /4) is compared with the unknown input. If greater then the second MSB=1, otherwise it is set to zero. The process is then repeated until the LSB is reached.