Attiny13 Software Uart Bascom

Micro ATTiny13 Servo Controller. Smallest, low cost 4-5 channel servo controller. And if you take a look of his page you even can use Half-duplex software UART.

Thank you so much for the nice work! I tried to compile the program using the command (I changed the value of the MCU to “MCU=attiny13a” in the uart.h file as well): $sudo avr-gcc -Wall -g -Os -mmcu=attiny13a -DF_CPU=1200000 -I.

Bascom and AVR, RS-232. Bascom and AVR, RS-232.

RS-232 RS-232 is nowadays a 'mature' communication standard. It is surprising that a standard, defined in the early sixties, is still widely used today. Formally however, the name RS-232 does not apply to a standard. An American organisation, now known as the Electronic Industries Association, proposed a way to communicate between large mainframe computers and peripheral equipment such as terminals. The proposal was called a Recommended Standard and 232 was not more than a identifying number.

Much later this became an official standard, EIA-232. In 1991, the latest version, EIA-232E was published. However, the name RS-232 is still widely used and so shall I in these pages. RS-232 is a serial communication protocol. It sends information as bit after bit and has two signal levels: - a voltage between -3 and -25 Volts is a logic one (1) - a voltage between +3 and +25 Volts is a logic zero (0) As the picture above shows, the voltage level between -3 and +3 Volts is undefined.

In practice this is not so. Most often, any voltage level above 2.5 Volts is seen as a logic zero, anything below as a logic one. The electrical specification of RS-232 is quite robust, all outputs must be able to sustain a full short-circuit and all inputs must have a schmitt-trigger action.

This makes a full-standard RS232 port on a PC much less vulnerable than a TTL-level parallel port. RS-232 is an a-synchronous protocol, meaning that no separate clock is transmitted with the data.

Both sides must know the communication speed (we use the term baud-rate) beforehand. In the original version of RS-232, a maximum speed of 20.000 bits per second was defined. Now, speeds up to 1 Mbit/s are used. RS-232 defines a complete hardware handshaking system using several wiring pins.

We use only the most important three: - RxD: receive data, pin number 2 - TxD: transmit data, pin number 3 - Ground, pin number 5 These pin numbers refer to a standard male DB9 connecter on your PC or laptop. UART UART means Universal Asynchronous Receiver Transmitter. It is the hardware end on both sides of an RS-232 communication link. In the PC or any other computer it is a chip on the motherboard under control of the CPU. In the AVR controller it is a small area on the chip die dedicated to this function.

In the AT90S2313 the UART is connected to pin 2 (RxD) and 3 (TxD). As these pins also function as general purpose I/O PortD.0 and PortD.1, you'll have to sacrifice some I/O if you need the UART. A UART takes care of sending and receiving bits.

When receiving, it determines when to sample the RxD pin to determine if a zero or one is received. When a complete byte has been received it can interrupt the controller to have this byte read from the UART input buffer. When transmitting, the UART reads a byte from the transmit buffer and sends the corresponding bits with the timing appropriate for the RS-232 speed selected. If the transmit buffer is empty the UART can interrupt the controller to send more bytes to the buffer if there are any. A UART does not do the level shifting needed to go from the AVR's logic level of 0 and +5 V to the RS-232 range of +3/+25 and -3/-25 Volts. This function is performed by chips like the ubiquitous MAX232 level converter: A level converter generates the voltages necessary to comply with the RS-232 levels.