Tag Archives: Com

CDC-232 – Virtual COM on ATMEL AVR


CDC-232 creates a virtual COM port on PC that doesn’t have real RS- 232C port. It enables RS-232C communication (without control lines), after connecting the device and installing the driver.

Write the program to AVR, build the circuit, and connect the device to PC’s USB port. Install the driver on Windows. Access the device through generated virtual COM port from terminal software or your application. Control lines (DTR, DTS, RTS, CTS) are not used by the host application. Set the terminal software as “no flow-control”.

Windows requests the driver installation again when connected to other USB port. Detect the previously installed driver automatically. Another COM number will be assigned. If you set serial number in AVR (rebuild with modified usbconfig.h), you can get the same COM port at any USB port. However, you cannot connect multiple CDC devices of the same serial number.

Before detaching the device, close the COM port in terminal software or in your application. Otherwise, you cannot connect to the device again because of the broken file handle. Restart the terminal software or your application then. Switch to the fast transfer mode using “lowcdc.vbs” to get the baudrate higher than 9600bps.

CDC-232 – Virtual COM on ATMEL AVR – [Link]

listComPorts – Windows command-line tool for USB-to-serial

listComPorts – Windows command-line tool for USB-to-serial @ todbot blog – [via]

Did you know each Arduino has a unique serial number in its USB interface that you can use to distinguish one Arduino from another? If you deal with multiple Arduinos, knowing exactly which one is plugged into your computer can be a real time-saver. But actually getting at this serial number and mapping it to COM ports can be challenging. For Windows computers, here’s “listComPorts

Serial port monitor – Peek at your COM ports!

Serial port monitor – Peek at your COM ports!… [via]

A while ago we did a tutorial on how to reverse engineer USB protocols using a USB logic analyzer, for when you have to develop your own USB drivers (say for a product that only comes with Microsoft support!) We also wanted to point out that if all you’re doing is debugging or reverse-engineering a basic product that uses serial (a COM port) you don’t need to shell out for a analyzer box! Instead you can use a serial port monitor, a piece of software that can spy on the COM port. These can also be handy when you have to debug software you wrote – to see what’s really going out on the hardware.

We tend to need to reverse-engineer stuff in windows so we use a nicely written piece of software called PortMon. Its a little old but it works great!

For example, while reverse engineering how to use our serial JPEG camera, we had a windows software that could control the camera but we wanted to port it to Arduino (or any microcontroller really). Since the software used a serial COM port, we started up PortMon, then started up the driver software

Then whenever data was sent back and forth, we’d get the data in HEX. For example here you can see the first READ (data sent out to the camera) as “76 00 31 00 00″ and the WRITE (reply from the camera to the computer “56 00 31 0C 01…

CommSniffer: COM/RS232 port data viewer

CommSniffer is a valuable tool for technicians, engineers and software developers designing/debugging serial port related projects, it is an advanced COM/RS232 Serial port data viewer / analyzer. View and send (all 256) ASCII/Binary data. Main features include:

  • Supports COM1 to COM16.
  • Baud rates from 110 to 115200.
  • Export transactions session to an ASCII file.
  • Designed for ease of use.
  • Ultra fast display rate.
  • Runs in Windows 9X/2000/XP.
  • Capture/send data to/from serial port.
  • Built in data converter ASCII/Binary/Hex.
  • Built in search.

CommSniffer: COM/RS232 port data viewer – [Link]

COM port powered temperature meter

This simple four channel temperature meter can be connected directly to your computer COM port and doesn’t require additional power supply. Check you computer back if there are any com ports before you start.

Temperature meter is based on ATtiny15L microcontroller which has built in ADC. Power for this circuit is taken from com port ER and RS signal lines. High level of these lines is from 6 to 12V and can supply up to 5mA of current. As L series microcontrollers are low power this is more than enough.

As temperature sensors there are four 103AT thermisters used. They give pretty good precision at room temperature (~0.3Cº). Author provides firmware for ATtiny15L and VBA project that logs temperature data to excel file. [via]

COM port powered temperature meter – [Link]

Simple USB to RS232 adapter on PIC18F2455


 As COM ports are disappearing form computers – especially from laptops, there are more and more USB to RS232(COM) adapters showing up in the Internet. The bigger choice the better to end user – he can look and build the best solution that fits his needs. This particular adapter was developed by Alex Sidorenko and its main purpose was to comply RS232 to USB of car ODB(On-Board Diagnostic) unit.

Simple USB to RS232 adapter on PIC18F2455 – [Link]


Build your own IrDA adaptor


New model PC mainboards have one on-board IrDA connector such ASUS. The IrDA function can enable by setting in BIOS with is changing the function of serial port between COMx and IrDA. With IrDA module you can download (i.e. ring tone,wall paper) or communication with devices that compliant to standard IrDA 1.2 such as mobile phone, Palm,Pocket PC,PDA.

Build your own IrDA adaptor – [Link1] [Link2]