Can't seem to consistently parse serial data from USB Modem

[foureight84]

I'm trying to test reading data from my USB modem (Conexant 56k data/fax) to grab incoming Caller ID but I am seeing that sometimes the parser will see the 'RING' data but a lot of times it won't at all. I am currently using version 10.5.0.

const { SerialPortStream } = require('@serialport/stream')
const { autoDetect } = require('@serialport/bindings-cpp')

const binding = autoDetect()

const options = {
    binding,
    path: '/dev/ttyACM0',
    baudRate: 57600,
    autoOpen: false
}

const port = new SerialPortStream(options)

port.open((err) => {
    if (err) return console.log('Error opening port: ', err.message)
    console.log('Port opened. Data Rate: ' + port.baudRate)

    port.set({
        cts: false,
        dsr: false,
        dtr: false,
        rts: false
    }, (err) => {
        if (err) return console.log('Failed to set options: ', err.message)
    })


})

port.on('open', () => {
    write('ATI0')
    write('ATZ')
    write('ATZ0')
    write('ATV1')
    write('AT+VCID=1')
    write('ATM0')
    write('AT&W0')
})

port.on('data', (data) => {
    console.log(data.toString())
})

port.on('close', () => {
    console.log('Port closed.')
})

port.on('error', (err) => {
    console.log('Serial port error: ' + err)
})

function write (command) {
    port.write(Buffer.from(command + '\r'), (err) => {
        if (err) return console.log('Error writing: ', err.message)
    })
    port.drain((err) => {
        if (err) return console.log('Drain error: ', err.message)
    })
}

Here's the output when RING is detected in a timely manner (masked out the caller id in NMBR) :

Port opened. Data Rate: 57600
ATI0
56000

OK

ATZ
OK

ATZ0
OK

ATV1
OK

AT+VCID=1
OK

ATM0
OK

AT&W0
OK


RING


DATE = 0427
TIME = 0406
NAME
 = O
NMBR = 1##########


RING


RING


DATE = 0427
TIME = 0406
NAME
 = O
NMBR = 1##########


RING

What happens is that most of the time the script will either display 'RING' after the second ring so the first ring and Caller ID were not parsed or it will never show anything at all. It's always able to parse the response 'OK' from write-commands without issues.

I've also tried using the InterByteTimeoutParser with various intervals with mixed results.

[foureight84]

I was able to get some debug data:

  serialport/bindings-cpp/poller received "readable" +18s
  serialport/bindings-cpp/unixRead Starting read +18s
  serialport/bindings-cpp/unixRead Finished read 8 bytes +1ms
  serialport/stream binding.read finished { bytesRead: 8 } +18s
  serialport/stream _read reading { start: 884, toRead: 64652 } +1ms
  serialport/bindings-cpp read +18s
  serialport/bindings-cpp/unixRead Starting read +2ms
  serialport/bindings-cpp/unixRead read error [Error: EAGAIN: resource temporarily unavailable, read] {
  errno: -11,
  code: 'EAGAIN',
  syscall: 'read'
} +1ms
  serialport/bindings-cpp/unixRead waiting for readable because of code: EAGAIN +0ms
  serialport/bindings-cpp/poller Polling for "readable" +5ms

RING

  serialport/bindings-cpp/poller received "readable" +991ms
  serialport/bindings-cpp/unixRead Starting read +993ms
  serialport/bindings-cpp/unixRead Finished read 32 bytes +0ms
  serialport/stream binding.read finished { bytesRead: 32 } +996ms
  serialport/stream _read reading { start: 916, toRead: 64620 } +0ms
  serialport/bindings-cpp read +996ms
  serialport/bindings-cpp/unixRead Starting read +2ms
  serialport/bindings-cpp/unixRead Finished read 26 bytes +0ms
  serialport/stream binding.read finished { bytesRead: 26 } +1ms
  serialport/stream _read reading { start: 942, toRead: 64594 } +1ms
  serialport/bindings-cpp read +1ms
  serialport/bindings-cpp/unixRead Starting read +1ms
  serialport/bindings-cpp/unixRead read error [Error: EAGAIN: resource temporarily unavailable, read] {
  errno: -11,
  code: 'EAGAIN',
  syscall: 'read'
} +1ms
  serialport/bindings-cpp/unixRead waiting for readable because of code: EAGAIN +0ms
  serialport/bindings-cpp/poller Polling for "readable" +5ms

DATE = 0501
TIME = 0249
NAME = O
NMBR = 1xxxxxxxxxx

I'm just trying to make sense of this and to understand why incoming rings to the modem and subsequent data to the serial port are not detected. In the data above, it was able to detect a ring, then the caller id data stream that's sent after the first ring. The rest of the rings after the caller id is no longer detected. I did notice that bindings-cpp read shows +996ms. Is the +996ms the time period from the last readable?

[foureight84]

After a bit of troubleshooting, I had a hunch it was related to the USB modem. I searched around and found that there is one existing firmware patch for this Zoom 3095 Connexant CDC ACM modem (link here should anyone come across this same issue https://legacysupport.minim.com/hc/en-us/articles/4416024460827-Hayes-Accura-V-92-USB-Mini-External-H08-15356-). The firmware patch note states: "This firmware patch fixes issues relating to faxing and low-speed applications." Either use minicom (linux) or Kitty (windows) to patch the firmware. The result is a consistent on-data event for incoming calls (vs. data not emitted by the device or a timing-related issue prior).

The firmware that came with the modem that exhibited inconsistent data transfer is F105C7 via Hayes AT-PV command. The firmware patch is F10572.