UART Library

The UART hardware module is available with a number of 8051 compliant MCUs. The mikroPascal PRO for 8051 UART Library provides comfortable work with the Asynchronous (full duplex) mode.

Library Routines

UARTx_Init
UARTx_Init_Advanced
UARTx_Data_Ready
UARTx_Read
UARTx_Read_Text
UARTx_Write
UARTx_Write_Text
UART_Set_Active

Notes:

UART routines require you to specify the module you want to use. To select the desired UART, simply change the letter x in the prototype for a number from 1 to 2.
Number of UART modules per MCU differs from chip to chip. Please, read the appropriate datasheet before utilizing this library.

Example: UART2_Init(9600); initializes UART 2 module at 9600 bps.
Some MCUs have multiple UART modules. Switching between the UART modules in the UART library is done by the UART_Set_Active function (UART module has to be previously initialized).
Some of the MCUs do not support UARTx_Init_Advanced routine. Please, refer to the appropriate datasheet.

UARTx_Init

Prototype	procedure UARTx_Init(baud_rate : longint);
Returns	Nothing.
Description	Configures and initializes the UART module. The internal UART module module is set to: receiver enabled frame size 8 bits 1 STOP bit parity mode disabled disabled automatic address recognition Parameters : `baud_rate:` requested baud rate Refer to the device datasheet for baud rates allowed for specific Fosc.
Requires	MCU with the UART module.
Example	// Initialize hardware UART1 and establish communication at 9600 bps UART1_Init(9600);

UARTx_Init_Advanced

Prototype

procedure UARTx_Init_Advanced(baud_rate : longint, adv_setting : byte);

Returns

Nothing.

Description

Configures and initializes UART module.

Parameters :

baud_rate sets the desired UART baud rate
adv_setting: UART module configuration flags. Predefined library constants (see the table below) can be ORed to form appropriate configuration value.

Description	Predefined library const
Parity constants:
`Parity mode disabled`	`_UART_NOPARITY`
`Even parity`	`_UART_EVENPARITY`
`Odd parity`	`_UART_ODDPARITY`
`Mark parity`	`_UART_MARKPARITY`
`Space parity`	`_UART_SPACEPARITY`
Stop bit constants:
`1 stop bit`	`_UART_ONE_STOPBIT`
`2 stop bits`	`_UART_TWO_STOPBITS`
Output mode constants:
`Output set as quasi-bidirectional (8051)`	`_UART_OUTPUT_8051`
`Output set as push-pull`	`_UART_OUTPUT_PUSH_PULL`
`Output set as open-drain`	`_UART_OUTPUT_OPEN_DRAIN`

Notes:

Some MCUs do not support advanced configuration of the UART module. Please consult appropriate datasheet.
Advanced parity and stop bit settings are supported by some Silicon Laboratories MCU's, while output settings by some ATMEL MCU's. Please, consult appropriate datasheet before using UARTx_Init_Advanced routine.

Requires

MCU must have UART module.

Example

// Initialize hardware UART1 module and establish communication at 9600 bps, 8-bit data, even parity and 2 STOP bits 
UART1_Init_Advanced(9600, _UART_EVENPARITY or _UART_TWO_STOPBITS);

UARTx_Data_Ready

Prototype	function UARTx_Data_Ready() as byte;
Returns	`1` if data is ready for reading `0` if there is no data in the receive register
Description	Use the function to test if data in receive buffer is ready for reading.
Requires	MCU with the UART module. The UART module must be initialized before using this routine. See UARTx_Init and UARTx_Init_Advanced routines.
Example	var receive: byte; ... // read data if ready if (UART1_Data_Ready() = 1) then receive := UART1_Read();

UARTx_Read

Prototype	function UARTx_Read() : byte
Returns	Returns the received byte.
Description	The function receives a byte via UART. Use the UARTx_Data_Ready function to test if data is ready first.
Requires	MCU with the UART module. The UART module must be initialized before using this routine. See UARTx_Init and UARTx_Init_Advanced routines.
Example	var receive: byte; ... // read data if ready if (UART1_Data_Ready() = 1) then receive := UART1_Read();

UARTx_Read_Text

Prototype	procedure UARTx_Read_Text(var Output : string[255]; var Delimiter : sting[10]; Attempts : byte);
Returns	Nothing.
Description	Reads characters received via UART until the delimiter sequence is detected. The read sequence is stored in the parameter `output`; delimiter sequence is stored in the parameter `delimiter`. This is a blocking call: the delimiter sequence is expected, otherwise the procedure exits( if the delimiter is not found). Parameter `Attempts` defines number of received characters in which `Delimiter` sequence is expected. If `Attempts` is set to 255, this routine will continuously try to detect the `Delimiter` sequence.
Requires	UART HW module must be initialized and communication established before using this function. See UARTx_Init.
Example	Read text until the sequence “OK” is received, and send back what’s been received: UART1_Init(4800); // initialize UART module Delay_ms(100); while TRUE do begin if (UART1_Data_Ready() = 1) then // if data is received begin UART1_Read_Text(output, 'OK', 10); // reads text until 'OK' is found UART1_Write_Text(output); // sends back text end; end;

UARTx_Write

Prototype	procedure UARTx_Write(data_ : byte);
Returns	Nothing.
Description	The function transmits a byte via the UART module. Parameters : `data_:` data to be sent
Requires	MCU with the UART module. The UART module must be initialized before using this routine. See UARTx_Init and UARTx_Init_Advanced routines.
Example	var data_: byte; ... data := 0x1E UART1_Write(data_);

UARTx_Write_Text

Prototype	procedure UARTx_Write_Text(var uart_text : string[255]);
Returns	Nothing.
Description	Sends text (parameter `uart_text`) via UART. Text should be zero terminated.
Requires	UART HW module must be initialized and communication established before using this function. See UARTx_Init.
Example	Read text until the sequence “OK” is received, and send back what’s been received: UART1_Init(4800); // initialize UART module Delay_ms(100); while TRUE do begin if (UART1_Data_Ready() = 1) then // if data is received begin UART1_Read_Text(output, 'OK', 10); // reads text until 'OK' is found UART1_Write_Text(output); // sends back text end; end;

UART_Set_Active

Prototype	procedure UART_Set_Active (read_ptr : ^TUART_Rd_Ptr; write_ptr : ^TUART_Wr_Ptr; ready_ptr : ^TUART_Rdy_Ptr);
Returns	Nothing.
Description	Sets active UART module which will be used by the UART library routines. Parameters : `read_ptr:` UARTx_Read handler `write_ptr:` UARTx_Write handler `ready_ptr:` UARTx_Data_Ready handler
Requires	Routine is available only for MCUs with two UART modules. Used UART module must be initialized before using this routine. See UARTx_Init routine
Example	UART1_Init(9600); // initialize UART1 module UART2_Init(9600); // initialize UART2 module RS485Master_Init(); // initialize MCU as Master UART_Set_Active(@UART1_Read, @UART1_Write, @UART1_Data_Ready); // set UART1 active RS485Master_Send(dat,1,160); // send message through UART1 UART_Set_Active(@UART2_Read, @UART2_Write, @UART2_Data_Ready); // set UART2 active RS485Master_Send(dat,1,160); // send message through UART2

UART_Data_Ready

Prototype	function UART_Data_Ready(): byte;
Returns	`1` if data is ready for reading `0` if there is no data in the receive register
Description	Use the function to test if data in receive buffer is ready for reading. This is a generic routine which uses the active UART module previously activated by the UART_Set_Active routine.
Requires	MCU with the UART module. The UART module must be initialized before using this routine. See the UARTx_Init routine.
Example	var receive: byte; ... // read data if ready if (UART_Data_Ready() = 1) then receive := UART_Read();

UART_Read

Prototype	function UART_Read(): byte;
Returns	Returns the received byte.
Description	The function receives a byte via UART. Use the UART_Data_Ready function to test if data is ready first. This is a generic routine which uses the active UART module previously activated by the UART_Set_Active routine.
Requires	MCU with the UART module. The UART module must be initialized before using this routine. See UARTx_Init routine.
Example	var receive: byte; ... // read data if ready if (UART_Data_Ready() = 1) then receive := UART_Read();

UART_Read_Text

Prototype	procedure UART_Read_Text(var Output, Delimiter : array[255] of byte; Attempts : byte);
Returns	Nothing.
Description	Reads characters received via UART until the delimiter sequence is detected. The read sequence is stored in the parameter `output`; delimiter sequence is stored in the parameter `delimiter`. This is a blocking call: the delimiter sequence is expected, otherwise the procedure exits( if the delimiter is not found). Parameter `Attempts` defines number of received characters in which `Delimiter` sequence is expected. If `Attempts` is set to 255, this routine will continuously try to detect the `Delimiter` sequence. This is a generic routine which uses the active UART module previously activated by the UART_Set_Active routine.
Requires	UART HW module must be initialized and communication established before using this function. See UARTx_Init.
Example	Read text until the sequence “OK” is received, and send back what’s been received: UART1_Init(4800); // initialize UART module Delay_ms(100); while TRUE do begin if (UART_Data_Ready() = 1) then // if data is received begin UART_Read_Text(output, 'OK', 10); // reads text until 'OK' is found UART_Write_Text(output); // sends back text end; end;

UART_Write

Prototype	procedure UART_Write(data_: byte);
Returns	Nothing.
Description	The function transmits a byte via the UART module. This is a generic routine which uses the active UART module previously activated by the UART_Set_Active routine. Parameters : `TxData:` data to be sent
Requires	MCU with the UART module. The UART module must be initialized before using this routine. See UARTx_Init routine.
Example	var data_: byte; ... data := 0x1E UART_Write(data_);

UART_Write_Text

Prototype	procedure UART_Write_Text(var uart_text : string);
Returns	Nothing.
Description	Sends text (parameter `uart_text`) via UART. Text should be zero terminated. This is a generic routine which uses the active UART module previously activated by the UART_Set_Active routine.
Requires	UART HW module must be initialized and communication established before using this function. See UARTx_Init.
Example	Read text until the sequence “OK” is received, and send back what’s been received: UART1_Init(4800); // initialize UART module Delay_ms(100); while TRUE do begin if (UART_Data_Ready() = 1) then // if data is received begin UART_Read_Text(output, 'OK', 10); // reads text until 'OK' is found UART_Write_Text(output); // sends back text end; end;

Library Example

This example demonstrates simple data exchange via UART. If MCU is connected to the PC, you can test the example from the mikroPascal PRO for 8051 USART Terminal.

program UART;
var uart_rd : byte;

begin
  UART1_Init(9600);                         // Initialize UART module at 9600 bps
  Delay_ms(100);                            // Wait for UART module to stabilize
  UART1_Write_Text('Ready');
  UART1_Write(10);
  UART1_Write(13);

  while (TRUE) do                           // Endless loop
    begin
      if (UART1_Data_Ready() <> 0) then     // If data is received,
        begin
          uart_rd := UART1_Read();          //   read the received data,
          UART1_Write(uart_rd);             //   and send data via UART
        end;
    end;
end.

HW Connection

UART HW connection

Want more examples and libraries?
Find them on