libserial: Portable Serial Port Access

7.7

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libserial: Portable Serial Port Access

Serial port handling for Racket utilizing "libserialport".

The libserialport itself is a minimal, cross-platform shared library written in C that is intended to take care of the OS-specific details when writing software that uses serial ports.

It must be installed externally to this Racket module, preferrably via the system package manager.

(require libserialport)

package: libserialport

A high-level interface to port enumeration, access and configuration.

syntax
Parity

Type for parity options. Equivalent to (U 'invalid 'none 'odd 'even 'mark 'space).

syntax
Flow-Control

Type for flow control options. Equivalent to (U 'none 'xonxoff 'rtscts 'dtrdsr).

procedure
(serial-ports) → (Listof Path-String)

Produce list of system serial port paths or names.

Example:

> (serial-ports)
'("/dev/ttyUSB0")

procedure
(in-serial-ports) → (Sequenceof Path-String)

Iterate over known serial port paths or names. Produces Path-String values.

Example:

> (for ((serial-port (in-serial-ports)))
(printf "found ~a\n" serial-port))
found /dev/ttyUSB0

procedure
(open-serial-port path
[ #:baudrate baudrate
#:bits bits
#:parity parity
#:stopbits stopbits
#:flowcontrol flowcontrol])
→
Input-Port Output-Port
  path : Path-String
  baudrate : Positive-Integer = 9600
  bits : Positive-Integer = 8
  parity : Parity = 'none
  stopbits : Natural = 1
  flowcontrol : Flow-Control = 'none

Opens (and configures) selected serial port for both reading and writing. The default options correspond to the most frequently used null-modem case typical for switches and other similar embedded devices.

Examples:

> (define-values (in out)
    (open-serial-port "/dev/ttyUSB0" #:baudrate 115200))
> (write-bytes #"x1AVx3\n" out)
7
> (let loop ()
    (define read-result (read-bytes-avail!* read-buffer port))
    (cond [(or (eof-object? read-result)
               (and (number? read-result) (not (= read-result 0))))
           (display (bytes->string/utf-8 (read-bytes read-result port)))
           (display "")]
          [else (sleep 0.1)])
    (loop))
eval: unable to replay evaluation of (let loop () (define
read-result (read-bytes-avail!* read-buffer port)) (cond
((or (eof-object? read-result) (and (number? read-result)
(not (= read-result 0)))) (display (bytes->string/utf-8
(read-bytes read-result port))) (display "")) (else (sleep
0....

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