> For the complete documentation index, see [llms.txt](https://docs.blynk.io/en/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.blynk.io/en/legacy-platform/legacy-articles/usb-serial.md).
# USB Serial
{% hint style="warning" %}
This documentation is for the LEGACY version of Blynk platform which is no longer supported and will be shut down.
You can sign up for the current version of Blynk platform [here](http://blynk.cloud/dashboard/register).
The new mobile apps can be downloaded from [App Store](https://apps.apple.com/us/app/blynk-iot/id1559317868) and [Google Play](https://play.google.com/store/apps/details?id=cloud.blynk\&hl=en\&gl=US).
The actual Blynk documentation is [here](https://docs.blynk.io/).
{% endhint %}
If you don't have any shield and your hardware doesn't have any connectivity, you can still use Blynk – directly over USB.
#### Getting Started
1. Optional, but recommended.Connect additional USB-Serial adapter to your device to see the debug prints.
2. Open [Arduino Serial USB example](https://github.com/blynkkk/blynk-library/blob/master/examples/Boards_USB_Serial/Arduino_Serial_USB/Arduino_Serial_USB.ino) and change [Auth Token](http://docs.blynk.cc/#getting-started-getting-started-with-application-4-auth-token)
3. Run the blynk-ser script, located in scripts folder:
* Windows: My Documents\Arduino\libraries\Blynk\scripts
* Mac: \~/Documents/Arduino/libraries/Blynk/scripts
* Linux: \~/Arduino/libraries/Blynk/scripts
The script is simply redirecting traffic to Blynk Cloud.
You can specify port, baud rate, and server endpoint like this:\
`./blynk-ser.sh -c -b -s -p `
For instance:\
`./blynk-ser.sh -c /dev/ttyACM0 -b 9600 -s blynk-cloud.com -p 8442`
Run `blynk-ser.sh -h` for more information
Be sure to select the right serial port (there may be multiple).\
\
**Attention!** Arduino IDE may complain with "programmer is not responding". You need to terminate script before uploading new sketch.
#### On Windows
Open `cmd.exe` (you may need to "Run as Administrator")\
Navigate to scripts folder:
```
cd C:\...\libraries\Blynk\scripts
```
Run `blynk-ser.bat` file. For example : `blynk-ser.bat -c COM4` (where COM4 is port with your Arduino)And press "Enter", press "Enter" and press "Enter"
#### On Linux and Mac
Navigate to scripts folder:
```
cd User$/Documents/Arduino/libraries/Blynk/scripts
```
When inside this folder, run:
```
user:scripts User$ ./blynk-ser.sh
```
You may need to run it with `sudo`:
```
user:scripts User$ sudo ./blynk-ser.sh
```
This is what you'll see in Terminal app on Mac (usbmodem address can be different):
```
[ Press Ctrl+C to exit ]
/dev/tty.usbmodem not found.
Select serial port [ /dev/tty.usbmodem1451 ]:
```
Copy the serial port address: `/dev/tty.usbmodem1451` and paste it back:
```
Select serial port [ /dev/tty.usbmodem1451 ]: /dev/tty.usbmodem1451
```
After you press Enter, you should see an output similar to this:
```
Resetting device /dev/tty.usbmodem1451...
Connecting: GOPEN:/dev/tty.usbmodem1451,raw,echo=0,clocal=1,cs8,nonblock=1,ixoff=0,ixon=0,ispeed=9600,ospeed=9600,crtscts=0 <-> openssl-connect:blynk-cloud.com:8441,cafile=/Users/.../server.crt,nodelay
2015/10/03 00:29:45 socat[30438.2046857984] N opening character device "/dev/tty.usbmodem1451" for reading and writing
2015/10/03 00:29:45 socat[30438.2046857984] N opening connection to LEN=16 AF=2 45.55.195.102:8441
2015/10/03 00:29:45 socat[30438.2046857984] N successfully connected from local address LEN=16 AF=2 192.168.0.2:56821
2015/10/03 00:29:45 socat[30438.2046857984] N SSL connection using AES128-SHA
2015/10/03 00:29:45 socat[30438.2046857984] N starting data transfer loop with FDs [3,3] and [4,4]
```
#### Additional materials:
* [Instructables: Control Arduino with Blynk over USB](http://www.instructables.com/id/Control-arduino-using-Blynk-over-usb/)
**Video tutorials :** \
---
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