USB Host Board - CDC Class Software

HobbyTronics USB Host Board - CDC Class Software
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Manufacturer: HobbyTronics
Average Rating: 5 out of 5 Stars!


USB Host Board - CDC Class Software

This software download is for our USB Host Board. It allows you to connect a CDC class device to the Host Board and send and receive data to the device via a serial TTL connection

This is a free software download for our USB Host Board and USB Host IC's (SOIC, DIP, SSOP).
To buy - See the USB Host Board and IC product pages (links on the pictures below) for details on pricing and installing this software.

Download Software
Click Here to Download V1.09
USB Host BoardUSB Host Mini
USB Host Boards
USB Host IC's

What is the CDC Class

The USB communications device class (or USB CDC) is a composite Universal Serial Bus device class. The class is used primarily for modems, but also for ISDN, fax machines, mobile phones and two way radios. The CDC class allows serial communication with these devices over a USB connection.

Now Supports Ublox USB GPS units

The CDC Class and Mobile Phones

Recent phones within the past 10 years or so, (but excluding all modern smart phones) that connect to a computer via a USB cable do so over a serial connection. Many of these phones supported  the USB Communications Device Class (CDC) ACM connection using standard Hayes type AT modem commands. We couldn't find a list of supported phones on the internet but Motorola, Samsung and Sony Ericsson phones supported this protocol (although we cannot guarantee a particular model will work)

We used a Motorola V3x

Non Supported Phones

All modern smartphones. That includes iPhones, Android, Blackberry. These phone use a proprietory communication system and will not work.

What can you do?

Sending and Receiving SMS Text messages via a microcontroller can be very useful for remote control or monitoring. You can use it for

  • Alarm System - Send an SMS Text Message to your mobile phone if an alarm is tripped
  • Remote Monitoring - Send remote data by SMS for monitoring say temperature  in a remote location
  • Control Equipment  - Send an SMS Text message to it to turn on/off an appliance

The USB Host Board will also charge your phone while it is plugged in so no worries about the battery going flat.


AVR323: Interfacing GSM modems

USB Host Board Configuration

The following Commands are available to configure the USB Host Board

These commands are used to configure the USB Host board and will only function when no device is plugged into the board. If a device is plugged in, these commands will be sent to the device

BAUD <value> Set Serial Port Baud Rate (default 9600)
Turn local Echo On or Off
HELP or ? Display help


The baud rate for communication with the board. Note that this does not effect the communications speed with the attached device.


This determines whether data sent to the board is echoed back by the board. This is useful when initially testing communication using a terminal program to issue commands.

When connected to a microcontroller you may not want the data sent to be echoed back. The default is ON

Connections required

  • 5V power in
  • 0V
  • TX out
  • RX in
  • SS pin goes high when CDC device inserted, low when removed

Example Communication with Mobile Phone

The following examples show how you can send and receive sms text messages using a Motorola mobile phone. Different models may have different commands so you should check online for the command list for your phone

First test communication by issuing the AT command. The mobile phone will normally echo the command sent and then send an OK response. E.g.


To stop the phone echoing your commands you can turn echo off with


Reading SMS Messages

The following commands are useful for reading text messages

	AT+CMGF=1              set to text mode
	AT+CMGL="REC UNREAD"   list all received unread 
                               - listing them marks them as read
	AT+CMGL="REC READ"     list all received read
	AT+CMGL="STO UNSENT"   list all stored unsent
	AT+CMGL="STO SENT"     list all stored sent
	AT+CMGL="ALL"          list all sms present
	AT+CMGR=1              read message number 1
	AT+CMGD=1              delete message 1

Example Communication

	+CMGL: 823,"REC READ","+447891123456"
	Hello there

Sending SMS Messages

To send an SMS message we use the AT+CMGS command to indicate the phone number to send the text to. The phone will respond with a > prompt. We can then send the text part of the message. Carriage returns sent will genereate another > prompt on a new line.

Complete sending the message by sending a Control-Z character

Example Communication

	> Hello this is a text

	> Next line
	+CMGS: 249


Deleting SMS Messages

	Use AT+CMGL="REC READ" to list messages

Delete a specific message using

	AT+CMGD=x    x=message number

Check on phone status


Get Date and time



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