vserialport

This is a wrapper of libserialport written in V. vserialport consists of the main datatype Port, and Configuration, EventSet, UsbBus and UsbID as secondary datatypes.

Construct and deconstruct the serial Port

Create a Port object by calling new_port. new_port requires port_name argument as string (such as devttyUSB0 or /dev/ttyS0) and returns optionally Port object. Use or to handle the error, in case it failes to create the Port object.

mut p1 := vserialport.new_port('/dev/ttyUSB1') or {
	code := vserialport.error_code()
	msg  := vserialport.error_message()
	println('>> [${code}]: ${msg}')
	println('Failed to open:\n\t${err.msg}')
	return
}

In case the object is created, make sure to call the destructor function free() to deallocate the Port object. A safer approach is to use defer.

p1.free()

Open and close the connection with serial port

Use p1.open() and p1.close() to open the connection with serial port and to disconnect the serial port. open(mode) requires vserialport.Mode argument and returns a boolean if it is connected or not. The other way to check if the Port is connected or not, use p1.is_connected() function.

enum Mode {
	read
	write
	read_write
}

Such as:

mut rc := int(0)
if p1.open(vserialport.Mode.read_write) == false {
	code := vserialport.error_code()
	msg  := vserialport.error_message()
	println('>> [${code}]: ${msg}')
	p1.free()
}
println('p1 port is connected = ${p1.is_connected()}')

Read / write functions

libserialport supports non-blocking and blocking read/write functions. The same approach is reflected on vserialport as well. write function requires the first argument of boolean type to be set, if the write function is blocking or non-blocking write to serial port, respectively - that is, block bool: true for blocking write function, and false for non blocking write function. If it is non-blocking write function, the third argument - the timeout_ms argument is not going to be taken into consideration. It is useful only for blocking write function. The second argument is the byte array to be sent. In case you have to send string, string provides the bytes() function, which returns the byte array of that string. The write functions returns optional integer - that is, either number of bytes that are written to the serial port or the error that needs to be handled with or operator.

Example 1:

// Use non-blocking write to sent string AT+R
rc := p1.write(false, 'AT+R\r'.bytes(), 0) or {
	println('faild to write')
	return
}
println('${rc} bytes are sent.)

Example 2

// Use blocking write (and wait 1000 ms) to send this byte array [0x01, 0x31, 0x31, 0x04]
rc := p1.write(true, [byte(0x01), 0x31, 0x31, 0x04], 1000) or {
	println('faild to write')
	return
}
println('${rc} bytes are sent.)

Function prototype for read/write.

write(block bool, buffer []byte, timeout_ms u32) ?int
read(mode ReaderMode, max_length u32, timeout_ms u32) []byte

In contrast with write function, the first argument of read function, instead of bool, requires mode as enum ReaderMode which has following three options:

enum ReaderMode{
	blocking    = 0
	next        = 1
	nonblocking = 2
}

Configuration functions

Use set_baudrate(), set_bits(), set_parity(), set_stopbits(), set_rts(vserialport.Rts), set_cts(vserialport.Cts), set_dtr(vserialport.Dtr), set_dsr(vserialport.Dsr), set_xon_xoff(vserialport.XonXoff) and set_flowcontrol(vserialport.FlowControl) to configure baudrate, bits, parity, stop bits, rts, cts, dtr, dsr, xon_xoff and flowcontrol, respectively.

Some other helping functions are:

function	return type	description
Port.name()	string	returns the name of serial port.
Port.description()	string	returns the description of serial port.
Port.transport()	enum Transport	returns the transport type of serial port. enum Transport {native, usb, bluetooth}
Port.usb_bus()	struct UsbBus	returns the usb bus and usb address.
Port.usb_id()	struct UsbId	returns the USB vendor ID and USB product ID.
Port.usb_manufacturer()	string	returns the USB manufacturer.
Port.usb_product()	string	returns the USB product.
Port.bluetooth_adress()	string	returns the bluetooth address as string.

Other functions

Function name	Return type	Description
Port.bytes_to_read()	int	Return the number of bytes waiting in the input buffer.
Port.bytes_to_write()	int	Return the number of bytes waiting in the output buffer.
Port.flush(Buffer)	bool	Flushes the Buffer.input, Buffer.output or Buffer.both and returns true if the selected buffer is flushed, otherwise false.
Port.drain()	false	Waits for the buffered data to be transmitted.
Port.signal()	enum Signal	Returns the status of control signal. This depends from the control signals that the serial port is configured. This may trigger as output Signal.cts, Signal.dsr, Signal.dcd or Signal.ri. If it failes to get the control signal, error needs to be handled with or operator.
Port.start_break	bool	Puts the serial port transmission line into the break state.
Port.end_break	bool	Takes the serial port tranmission line out of the break state.

Other helping function from vserialport:

Function name	Return type	Description
error_code()	int	Returns the last error code.
error_message()	string	Returns the last error message.
major_version()	int	Returns the major package version of libserialport.
minor_version()	int	Returns the minor package version of libserialport.
micro_version()	int	Returns the micro package version of libserialport.
package_version()	string	Returns the full package version of libserialport

Depedencies

• libserialport

Bugfix

If you install the libserialport using apt-get install libserialport*, you may have to deal with following error: "Inappropriate ioctl for device". To avoid this error, make sure to install the libserialport from the github repository. More specifically, make sure that the following patch is applied (patch):

configure.ac | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index b1af16f..a26b851 100644
--- a/configure.ac
+++ b/configure.ac
@@ -112,7 +112,7 @@ AC_SYS_LARGEFILE
 AC_TYPE_SIZE_T
 
 # Check for specific termios structures.
-AC_CHECK_TYPES([struct termios2, struct termiox],,,
+AC_CHECK_TYPES([struct termios2],,,
 	[[#include <linux/termios.h>]])
 AC_CHECK_MEMBERS([struct termios.c_ispeed, struct termios.c_ospeed,
 		struct termios2.c_ispeed, struct termios2.c_ospeed],,,

Roadmap

• Writing the wrapper.
• Testing main functions of Port struct.
• Testing other function of Port struct.
• Full testing of Configuration struct.
• Full testing of EventSet struct.
• Multithreading/concurrency.
• Testing on Windows OS.
• Testing on Linux OS.

WARNING

This wrapper is not yet fully validated enough to be implemented in the application industry.