UART Library

The UART hardware module is available with a number of 8051 compliant MCUs. The mikroC 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	void UARTx_Init(unsigned long baud_rate);
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

void UARTx_Init_Advanced(unsigned long baud_rate, char adv_setting);

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, _UART_TWO_STOPBITS);

UARTx_Data_Ready

Prototype	char UARTx_Data_Ready();
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	char receive; ... // read data if ready if (UART1_Data_Ready()) receive = UART1_Read();

UARTx_Read

Prototype	char UARTx_Read();
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	char receive; ... // read data if ready if (UART1_Data_Ready()) receive = UART1_Read();

UARTx_Read_Text

Prototype	void UARTx_Read_Text(char Output, char* Delimiter, char* Attempts);
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). Parameters : `Output:` received text `Delimiter:` sequence of characters that identifies the end of a received string `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 and UARTx_Init_Advanced routines.
Example	Read text until the sequence “OK” is received, and send back what’s been received: UART1_Init(4800); // initialize UART1 module Delay_ms(100); while (1) { if (UART1_Data_Ready() == 1) { // if data is received UART1_Read_Text(output, "OK", 10); // reads text until 'OK' is found UART1_Write_Text(output); // sends back text } }

UARTx_Write

Prototype	void UARTx_Write(char _data);
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	unsigned char _data = 0x1E; ... UART1_Write(_data);

UARTx_Write_Text

Prototype	void UARTx_Write_Text(char * UART_text);
Returns	Nothing.
Description	Sends text via UART. Text should be zero terminated. Parameters : `UART_text:` text to be sent
Requires	UART HW module must be initialized and communication established before using this function. See UARTx_Init and UARTx_Init_Advanced routines.
Example	Read text until the sequence “OK” is received, and send back what’s been received: UART1_Init(4800); // initialize UART1 module Delay_ms(100); while (1) { if (UART1_Data_Ready() == 1) { // if data is received UART1_Read_Text(output, "OK", 10); // reads text until 'OK' is found UART1_Write_Text(output); // sends back text } }

UART_Set_Active

Prototype	void UART_Set_Active(char (read_ptr)(), void* (write_ptr)(unsigned char* data_), char (*ready_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 and UARTx_Init_Advanced routines.
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	char UART_Data_Ready();
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	UART HW module must be initialized and communication established before using this function. See UARTx_Init.
Example	// If data is ready, read it: if (UART_Data_Ready() == 1) { receive = UART_Read(); }

UART_Read

Prototype	char UART_Read();
Returns	Returns the received byte.
Description	Function receives a byte via UART. Use the function UART_Data_Ready 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	UART HW module must be initialized and communication established before using this function. See UARTx_Init.
Example	// If data is ready, read it: if (UART_Data_Ready() == 1) { receive = UART_Read(); }

UART_Read_Text

Prototype	void UART_Read_Text(char Output, char* Delimiter, char* Attempts);
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). This is a generic routine which uses the active UART module previously activated by the UART_Set_Active routine. Parameters : `Output:` received text `Delimiter:` sequence of characters that identifies the end of a received string `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 UART1 module Delay_ms(100); while (1) { if (UART_Data_Ready() == 1) { // if data is received UART_Read_Text(output, "OK", 10); // reads text until 'OK' is found UART_Write_Text(output); // sends back text } }

UART_Write

Prototype	void UART_Write(char data_);
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 : `_data:` data to be sent
Requires	UART HW module must be initialized and communication established before using this function. See UARTx_Init.
Example	unsigned char _data = 0x1E; ... UART_Write(_data);

UART_Write_Text

Prototype	void UART_Write_Text(char *UART_text);
Returns	Nothing.
Description	Sends 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. Parameters : `UART_text:` text to be sent
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 UART1 module Delay_ms(100); while (1) { if (UART_Data_Ready() == 1) { // if data is received UART_Read_Text(output, "OK", 10); // reads text until 'OK' is found UART_Write_Text(output); // sends back text } }

Library Example

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

char uart_rd;

void main() {
  
  UART1_Init(4800);               // Initialize UART module at 4800 bps
  Delay_ms(100);                  // Wait for UART module to stabilize
  
  UART1_Write_Text("Start");
  while (1) {                     // Endless loop
    if (UART1_Data_Ready()) {     // If data is received,
      uart_rd = UART1_Read();     //   read the received data,
      UART1_Write(uart_rd);       //   and send data via UART
    }
  }
}

HW Connection

UART HW connection

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