Port will not open if executing from file

[micromashor]

Summary of Problem

(Please answer all 3)

• What are you trying to do?
  Open a port and write data to it
• What happens?
  If using the node command and typing program line-by line, port opens and it works correctly.
  If executing from file, port never opens and data cannot be written.
• What should have happened?
  Port should have opened.

Code to Reproduce the Issue

const SerialPort = require('serialport')
port = new SerialPort('COM4', { baudRate: 115200 })

console.log(port)
console.log(port.isOpen)

while(!port.isOpen) {}

console.log('port open')

port.write("CFEFEFE")

Versions, Operating System and Hardware

• SerialPort@? v6.14.10
• Node.js v? v14.15.4
• Windows? Linux? Mac? windows 10
• Hardware and chipset? (Prolific/FTDI/Other) ATMEGA 16u2 on Arduino Uno R3

[micromashor]

I've figured out a workaround for the time being, using the child_process library.

const { exec } = require('child_process')

exec('echo CFFFFFF > COM4', {'shell':'cmd.exe'})

The serial port can be configured using:

exec('mode COM4 BAUD=115200 PARITY=n DATA=8 STOP=1 to=off xon=off odsr=off octs=off dtr=off rts=off idsr=off', {'shell':'cmd.exe'})

Composing those commands using basic string composition, you can get all of the functionality of Writing to the serial port. Reading is still off the table as far as I can tell, since I can't get serialport to open the port.

[reconbot]

Like if you put it in a .js file? Is it possible you're not using the same version of node? How are you executing it?

[micromashor]

I've gotten it to open from file (seemed to be an issue with the 'open' event), but it seems to be overwriting the DTR circuit setting. Executing mode COM4 dtr=off would fix this outside of the library. Every time data is written to the port, the DTR line gets activated, which promptly resets the Arduino on the receiving end.

Just as there is a boolean for rtscts, there should be a boolean for dtrdsr.