Syntax:
Used as subroutine:
HSerReceive (user_byte_variable)or, if other multiple comports are in use, set the comport before using HSerReceive.
comport = 1 '(1|2|3|4|5)Not needed unless using multiple comports in use
HSerReceive (_user_byte_variable_)or, used as function.
user_byte_variable =HSerReceive'Supports only USART1 user_byte_variable =HSerReceive1'Supports only USART1 user_byte_variable =HSerReceive2'Supports only USART2
or, used to support assigning of received byte to word (or other multi-byte variables). Note the use of casting to ensure
the HSerReceive uses byte addressing.
Dim dbAdr as Word HSerReceive [byte]dbAdr_H HSerReceive [byte]dbAdr
For other comports use Function HSerReceiveFrom
Command Availability:
Available on all microcontrollers with a USART or UART module.
Microchip PIC supports USART1,2,3,4 and 5.
Atmel AVR supports USART 1,2,3 and 4.
Enabling Constants:
To enable the use of the USART these are the enabling constants. These constants are required. You can change the USART_BAUD_RATE and to meet your needs. For addition USART ports use #define USARTn_BAUD_RATE 9600 where n` is the required port number.
'USART settings for USART1
#define USART_BAUD_RATE 9600 'Set the baud rate
#define USART_TX_BLOCKING 'Ensure the transmit buffer is empty
#define USART_BLOCKING 'Ensures a data byte is in the receive buffer
#define USART_DELAY OFF 'Disables USART delaysExplanation:
This command will read a byte from the hardware RS232 module. It can be used either as a subroutine or as a function. If used as a subroutine, a variable must be supplied to store the received value in. If used as a function, it will return the received value.
The subroutine HSerReceive can get a byte from any comport but must set the comport number immediately before the call. If ”#define USART_BLOCKING” is defined then the HserReceive waits in a loop until it receives a byte. If” #define USART_BLOCKING” is NOT defined then HserReceive returns the new byte that was received OR returns 255 because of “DefaultUsartReturnValue = 255” was defined. This is good because it don’t hold up your program from executing other commands and your can check it for new data priodically.
Example:
'This program will read a value from the USART, and send it to PORTB.
#chip 16F877A, 20
'USART settings
#define USART_BAUD_RATE 9600 'sets up comport 1 for 9600 baud
'Set PORTB to output
Dir PORTB Out
'Set USART receive pin to input
Dir PORTC.7 In
'Main loop
Do
'Get serial data and output value to PortB as 8 bit binary
HSerReceive(InChar) 'Receive data as Subroutine from comport 1
'InChar = HSerReceive 'Could also be written as Function
If InChar <> 255 Then 'If value is 255 then it is old data
PortB = InChar 'If new data then it goes to PortB
End If
LoopExample 2:
'If you choose no “Blocking” and comment both of them out.
'USART settings
#define USART_BAUD_RATE 9600
'#define USART_BLOCKING ' just none OR one of the blocking
'#define USART_TX_BLOCKING ' statements should be defined
'Main loop
Do
'Get and display value
'If there is no new data, HSerReceive will return default value.
comport = 1
HSerReceive tempvalue
If tempvalue <> 255 Then ‘ don’t change PortB if it is default
PortB = tempvalue
End If
LoopExample 3:
'If you choose no “Blocking” and comment both of them out.
#chip mega328p, 16
#define USART_BAUD_RATE 9600
'#define USART_BLOCKING
'#define USART_TX_BLOCKING
'Don't forget to Set usart pin directions
Dir PortD.1 Out 'com1 USART0
Dir PortD.0 In
Wait 1 s
'Message after reset
HSerPrint "ATmega328P com test"
HSerPrintCRLF
'Main routine hook up FTDI232 usb to serial and use terminal program to check
Start:
comport = 1
HSerReceive(InChar) 'Subroutine needs the comport set
'InChar = HSerReceive ' This function will get from comport 1
If InChar <> 255 Then ' check if for received byte
'return 255 if old data
HSerSend InChar 'send back char to UART
End If
Goto StartSee also RS232 Hardware Overview
