rs232_software_overview_optimised

RS232 Software Overview - Optimised

Introduction:

These routines allow the microcontroller to send and receive RS232 data.

SoftSerial is a library for the Creat Cow BASIC compiler and works on AVR and PIC microcontrollers. These routines allow the microcontroller to send and receive RS232 data. All functions are implemented using software, so no special hardware is required on the microcontroller. SoftSerial uses ASM routines for minimal overhead. If the microcontroller has a hardware serial module (usually referred to as UART or USART) the hardware routines can be used too.

Features

• 3 independent channels Ser1…​ , Ser2…​ , Ser3…​

• I/O pins user configurable

• polarity can be inverted

• freely adjustable baud rate

• maximum baudrate depends on MCU speed

  • PIC@ 1Mhz 9600 baud
  • PIC@ 4Mhz 38400 baud
  • PIC@ 8Mhz 64000 baud
  • PIC@16Mhz 128000 baud
  • AVR@ 1Mhz 28800 baud
  • AVR@ 8Mhz 115200 baud
  • AVR@16Mhz 460800 baud

• 5 - 8 data bits

• 1 or 2 stop bits

• parity bit not supported

Relevant Constants:

These constants are used to control settings for the RS232 serial communication routines. To set them, place a line in the main program file that uses #define to assign a value to the particular constant.

Constant Name/s	Controls	Valid Values	Default value
SER1_TXPORT, SER2_TXPORT, SER3_TXPORT	These are used to define the port for sending on serial channels 1, 2 and 3 respectively. Note, that we also have to define a PortPin (see next line). It is not necessary to define this, if we want to receive only. Sample: #define SER1_TXPORT PortB	PORTA - PORTx	No default defined. An appropiate constant must be defined.
SER1_TXPIN, SER2_TXPIN, SER3_TXPIN	These are used to define the pin (the corresponding bit) for sending on serial channels 1, 2 and 3 respectively. Sample: #define SER1_TXPIN 0	0 - 7	No default defined. An appropiate constant must be defined to enable the TX port.
SER1_RXPORT, SER2_RXPORT, SER3_RXPORT	These are used to define the port for receiving on serial channels 1, 2 and 3 respectively. Note, that we also have to define a PortPin (see next line). It is not necessary to define this, if we want to receive only. Sample: #define SER1_RXPORT PortA	PORTA - PORTx	No default defined. An appropiate constant must be defined to enable the TX port.
SER1_RXPIN, SER2_RXPIN, SER3_RXPIN	These are used to define the pin (the corresponding bit) for receiving on serial channels 1, 2 and 3 respectively. It is not necessary to define this, if we want to send only. Sample: #define SER1_RXPIN 5	0 - 7	No default defined. An appropiate constant must be defined to enable the RX port.
SER1_BAUD, SER2_BAUD, SER3_BAUD	These are used to define the baudrate for sending and receiving on serial channels 1, 2 and 3 respectively. It is not necessary to define this, if we want to send only. Sample: #define SER1_BAUD 19200	75 - 512000	No default defined. An appropiate constant must be defined to enable the RX port.
SER1_DATABITS, SER2_DATABITS, SER3_DATABITS	These are used to define the databits for sending and receiving on serial channels 1, 2 and 3 respectively. Sample: #define SER1_DATABITS 7	5 - 8	Optional Default = 8
SER1_STOPBITS, SER2_STOPBITS, SER3_STOPBITS	These are used to define the stopbits for sending and receiving on serial channels 1, 2 and 3 respectively. Sample: #define SER1_STOPBITS 2	1, 2	Optional Default = 1
SER1_INVERT, SER2_INVERT, SER3_INVERT	These are used to define the polarity for sending and receiving on serial channels 1, 2 and 3 respectively. If it is "On", then high bits will be changed to low, and low to high. This is useful for connection to a PCs native serial port or USB-serial converters with MAX232. Sample: #define SER1_INVERT On	On, Off	Optional Default = Off
SER1_RXNOWAIT, SER2_RXNOWAIT, SER3_RXNOWAIT	These are used to define, if SerNReceive waits for the startbits when receiving on serial channels 1, 2 and 3 respectively. If it is "On", then SerNReceive does not wait for the startbits edge, but directly reads the serial data. Also the time for delaying the startbit is shortened. This is useful when calling SerNReceive from an Interrupt-Service-Routine. Sample: #define SER1_RXNOWAIT On	On, Off	Optional Default = Off