Software UART Library

The mikroPascal PRO for ARM provides routines for implementing Software UART communication. These routines are hardware independent and can be used with any MCU. The Software UART Library provides easy communication with other devices via the RS232 protocol.

Important : The Software UART library implements time-based activities, so interrupts need to be disabled when using it.

Soft_UART_Init

Prototype	function Soft_UART_Init(var port: dword; rx, tx: dword; baud_rate : dword; inverted : word) : byte;
Description	Configures and initializes the software UART module. Software UART routines use Delay_Cyc routine. If requested baud rate is too low then calculated parameter for calling `Delay_Cyc` exceeds `Delay_Cyc` argument range. If requested baud rate is too high then rounding error of `Delay_Cyc` argument corrupts Software UART timings.
Parameters	`port:` software UART port address `rx:` receiver pin `tx:` transmiter pin `baud_rate:` requested baudrate. Maximum baud rate depends on the MCU’s clock and working conditions `inverted:` if set to non-zero value, indicates inverted logic on output
Returns	`2` - error, requested baud rate is too low `1` - error, requested baud rate is too high `0` - successful initialization
Requires	Nothing.
Example	This will initialize software UART and establish the communication at 56000 bps: Stellaris error := Soft_UART_Init(GPIO_PORTA, 0, 1, 56000, 0); // Initialize Soft UART at 56000 bps STM32 error := Soft_UART_Init(GPIOA_ODR, 10, 9, 115200, 0); // Initialize Soft UART at 56000 bps
Notes	The Software UART library implements time-based activities, so interrupts need to be disabled when using it.

Soft_UART_Read

Prototype	function Soft_UART_Read(var error : byte) : byte;
Description	The function receives a byte via software UART. This is a blocking function call (waits for start bit). Programmer can unblock it by calling Soft_UART_Break routine.
Parameters	`error:` Error flag. Error code is returned through this variable. Values : `0` - no error `1` - stop bit error `255` - user abort, Soft_UART_Break called
Returns	Byte received via UART.
Requires	Software UART must be initialized before using this function. See the Soft_UART_Init routine.
Example	var data_ : byte; error : word; ... // wait until data is received repeat data_ := Soft_UART_Read(error); until (error = 0); // Now we can work with data: if (data_) then begin ... end
Notes	The Software UART library implements time-based activities, so interrupts need to be disabled when using it.

Soft_UART_Write

Prototype	procedure Soft_UART_Write(udata : byte);
Description	This routine sends one byte via the Software UART bus.
Parameters	`udata:` data to be sent.
Returns	Nothing.
Requires	Software UART must be initialized before using this function. See the Soft_UART_Init routine. Be aware that during transmission, software UART is incapable of receiving data – data transfer protocol must be set in such a way to prevent loss of information.
Example	var some_byte : byte; ... some_byte := $0A; // Write a byte via Soft UART Soft_UART_Write(some_byte);
Notes	The Software UART library implements time-based activities, so interrupts need to be disabled when using it.

Soft_UART_Break

Prototype	procedure Soft_UART_Break();
Description	Soft_UART_Read is blocking routine and it can block the program flow. Calling `Soft_UART_Break` routine from the interrupt will unblock the program execution. This mechanism is similar to WDT.
Parameters	None.
Returns	Nothing.
Requires	Nothing.
Example
Notes	The Software UART library implements time-based activities, so interrupts need to be disabled when using it.

Library Example

This example demonstrates simple data exchange via software UART. If MCU is connected to the PC, you can test the example from the mikroPascal PRO for ARM USART communication terminal, launch it from the drop-down menu Tools › USART Terminal or simply click the USART Terminal Icon .

Stellaris

Copy Code To Clipboard

program Soft_UART;

var error : byte;
    counter, byte_read : byte;             // Auxiliary variables

begin
  GPIO_Digital_Output(@GPIO_PORTD, _GPIO_PINMASK_ALL); // digitalni output
  GPIO_PORTD_DATA := 0;

  error := Soft_UART_Init(GPIO_PORTA, 0, 1, 56000, 0); // Initialize Soft UART at 56000 bps
  if (error > 0) then
    begin
      GPIO_PORTD_DATA := error;            // Signalize Init error
      while (TRUE) do nop;                 // Stop program
    end;
  Delay_ms(100);

  for counter := 'z' downto 'A' do         // Send bytes from 'z' downto 'A'
    begin
      Soft_UART_Write(counter);
      Delay_ms(100);
    end;

  while TRUE do                            // Endless loop
    begin
      byte_read := Soft_UART_Read(error);  // Read byte, then test error flag
      if (error <> 0) then                 // If error was detected
        GPIO_PORTD_DATA := error           //   signal it on GPIO_PORTD
      else
        Soft_UART_Write(byte_read);        // If error was not detected, return byte read
    end;
end.

STM32

Copy Code To Clipboard

program Soft_UART;

var error : byte;
    counter, byte_read : byte;             // Auxiliary variables

begin
  GPIO_Digital_Output(@GPIOD_BASE, _GPIO_PINMASK_ALL); // digitalni output
  GPIOD_ODR := 0;

  error := Soft_UART_Init(GPIOA_ODR, 10, 9, 115200, 0); // Initialize Soft UART at 56000 bps
  if (error > 0) then
    begin
      GPIOD_ODR := error;            // Signalize Init error
      while (TRUE) do nop;                 // Stop program
    end;
  Delay_ms(100);

  for counter := 'z' downto 'A' do         // Send bytes from 'z' downto 'A'
    begin
      Soft_UART_Write(counter);
      Delay_ms(100);
    end;

  while TRUE do                            // Endless loop
    begin
      byte_read := Soft_UART_Read(error);  // Read byte, then test error flag
      if (error <> 0) then                 // If error was detected
        GPIOD_ODR := error           //   signal it on PORTD
      else
        Soft_UART_Write(byte_read);        // If error was not detected, return byte read
    end;
end.

Want more examples and libraries?
Find them on