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
Please note: This software is free to download but only works on one of our USB boards or chips which must be bought separately.
To order, simply select which of our boards or IC products you wish to have the software loaded onto. See the USB Host Board and IC product pages for details on pricing and installing this software.
NOTE: The CDC class functionality has now been incorporated into the SERIAL software. No further development will be done on the CDC software.
What is the CDC Class
The USB communications device class (or USB CDC) is a composite Universal Serial Bus device class. It is used for modems, mobile phones, two way radios and many other generic serial devices.
The CDC class is also used by Arduino boards (genuine boards not clones) and Teensy boards, which are supported in this software
Now Supports Ublox USB GPS units
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
|Set Serial Port Baud Rate (default 9600)
|Turn local Echo On or Off
|CDC Communication settings (default 0)
This is for transmission TO the attached USB CDC device.
0 – TEXT mode. Data is transmitted once carriage return is received
1 – BYTE mode. Each character is transmitted as it is received
2 – PACKET mode.
|Set Serial Port Configuration
0 – default TTL (positive logic)
1 – RS232 (negative logic)
|HELP or ?
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
This determines the type of communication with the CDC device.
This is for transmission TO the attached USB CDC device only. Data FROM the CD device is not affected by these settings.
0 – TEXT mode
Data is transmitted once carriage return is sent
1 – BYTE mode
Each character is transmitted as it is received
2 – PACKET mode
Similar to byte mode, but data is sent once a complete packet of data is received. This is useful for binary data transfer.
The first byte of the packet data is the data length (excluding itself). This is not transmitted.
For instance to transmit the four bytes 0x0A 0x0B 0x0C 0x0D you would send
0x04 0x0A 0x0B 0x0C 0x0D
The packet of data is transmitted once all data bytes have been received.
RS232 Port Configuration
You can now set the serial port to RS232 negative logic (local – not the attached USB device). This will enable you to connect the board directly to serial ports that support the RS232 negative logic format.
There are a few important points to bear in mind
- This does not effect the bootloader, so program updates will still need a positive logic TTL connection
- Once you have activated RS232 mode, you will need to communicate with the Host board/chip using RS232
- RS232 is negative logic, but the host chip will only provide 0V and 3.3V output. It will not produce negative voltages
- Do not connect to RS232 ports that have high voltages – e.g. old style PC serial ports which operate at +/- 12V
- 5V power in
- TX out
- RX in
- SS pin goes high when CDC device inserted, low when removed
The CDC Class and Mobile Phones
Mobile phones (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 to test mobile phone connectivity
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.
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
+CMGL: 823,"REC READ","+447891123456"
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
> Hello this is a text
> Next line
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