# Desargues configuration

The Desargues configuration as two pentagons written inside each other.

Non-Desargues (103103) configurations can also be considered as nested pentagons.

Pass through point D the lines c1, c2 and c3. On these lines, take points A1, A2 and A3 in order, and points B1, B2 and B3. Let C3 be the intersection of lines A1A2 and B1B2, C2 the intersection of lines A2A3 and B2B3, and C1 the intersection of lines A1A3 and B1B3.

If C1, C2 and C3 fall on a line, then these points and lines form a Desargues configuration. If this construction yields a Desargues configuration in all cases, then the Desargues theorem is satisfied for the plane.

The notation for the projective Desargues configuration is (103103), which means that there are ten lines, ten points, and three points for each line, and three figuratio bt lines for each point. These ten points can be considered as two pentagons written into each other, or as a decagon written into itself. (Hilbert and Cohn-Vossen 1952) We say that two polygons are inscribed if the vertices of one of them fit the side lines of the other, and vice versa. The Levi-graph of the configuration is the 3-regular symmetric pairwise Desargues graph with 20 vertices, where the vertices correspond to the point and the lines of the configuration and the edges correspond to the matching relation.

In addition, there are eight other (103103)-configurations which are not isomorphic to the Desargues configuration. In these configurations, for each point there are three other points that do not coincide with it and form a triangle, whereas in the Desargues configurations they always fit a line. They can also be considered as interlaced pentagons.

### Microcontroller

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Atmel ATTiny2313 type 8-bit microcontroller in DIP-20 package

A microcontroller or microcontroller is a target computer integrated on a single board, usually optimized for control tasks. A microcontroller is a microprocessor with peripherals integrated figuratio bt on its circuit board. Nowadays, many everyday devices use microcontrollers, from digital thermometers to cars to fast-food souvenir games.

In the past, types of microprocessor were used to perform control tasks. When a microprocessor was used, additional integrated circuits (ICs) had to be built in because of the peripherals required. With advances in circuit technology, more and more peripherals could be integrated into ICs, thus the microcontroller figuratio bt was developed, resulting in a very compact circuit.

### The microcontroller

It can cost-effectively perform simple operations requiring low computational power and operational memory. The design aims at solving the widest range of tasks with as few additional components as possible, while minimising the power consumption, size and cost of the device. This is achieved by multiplexing the IC legs and using integrated peripherals. The legs of the circuit case can be programmatically connected to the I/Os of the internal peripherals, or they can be set/read directly by the microcontroller program. Today's (2013) typical microcontroller runs at 1-100 MHz clock speed, contains 100 bytes to 100 kBytes of flash memory, and RAM ranging in size from a dozen bytes to a few 100 kBytes. Their typical supply voltage is 1.8 V...3.3 V...5 V, their maximum current consumption is in the range of 100 mA, and the number of encapsulation feet is figuratio bt between 8 and a few hundred feet. Based on the internal data size, a distinction can be made between 8, 16 and 32-bit microcontrollers.

Microcontrollers are generally used for real-time tasks, where some environmental signal has to be responded to within a very short time (usually milliseconds to milliseconds). Usually they do not have an operating system, but run a program written for the specific target task.

The actuator program is loaded into the microcontroller either in a separate programming device as for *PROMs (PROM, EPROM, EEPROM), or by mask programming as ISP (In System Programming) in the final circuit, or in large series, at the same time as the microcontroller is produced. The old figuratio bt types were programmable once, but the new devices virtually all contain a Flash-ROM based program memory, so they can tolerate up to many thousands of write/erase cycles. They are programmed either by machine code (assembler) instructions, like microprocessors, or in their own programming language, or in the case of larger microcontrollers, in a high-level programming language such as C.

### Its components (peripherals)

A microcontroller may contain many peripherals, depending on the task to be performed. Each peripheral has a power consumption (depending on the state of the peripheral and its settings), which add up to increase the total power consumption of the microcontroller. In order to avoid unnecessary consumption, each peripheral can be switched off and on even while the program is running.

Common peripherals:

oscillator: provides a figuratio bt clock signal to the processor and can also be used for timing by controlling a counter

Operational memory to store the control program ROM and run-time data RAM

counters/timers: these can be stepped by external and internal signals. They can also be used for simple pulse counting tasks and frequency measurement

watchdog timer: a safety device against freezing of the actuator program. figuratio bt A timer which is periodically reset by the software. If it does not, the watchdog circuitry will hardware restart the microcontroller, which may remove the condition that caused the freeze.

EEPROM memory: used to store calibration data or other parameters and data. It retains its contents even after loss of power.

DSP (digital signal processor): a computing unit that accelerates the special computing operations required for high-speed digital signal processing

Transducers:

Analog-to-digital converter (A/D converter) converts external analog signals (voltage) into digital form that can be processed by the processor

Digital-to-analogue converter (D/A converter) converts internal digital signals into analogue signals.

Comparator: compares two analogue voltages.

Communication interfaces Buses: they enable different devices to communicate with each other.

I2C (Inter-Integrated Circuit) bus,

SPI (Serial Peripheral Interface) bus,

CAN (Controller Area Network) bus,

Ethernet,

1-Wire,

USB,

parallel port external parallel bus

Memory-type memory management

parallel data and address bus memory management

SD card management

Drive units:

LCD panel drives

LED display drives

Signal generators:

PWM: square wave signal adjustment with appropriate padding, usually for power control

debug interface: for debugging the microcontroller and monitoring program status. Allows the program to run while connected to a computer. This allows you to monitor the characteristics of the running program: registers, memory, etc. The program can be stopped and restarted.