BV4221	USB to I2C converter and inspector	Datasheet	£17.98
	The BV4221 is a device for using I2C compatible equipment via USB. It provides a terminal like interface and is primarily intended for debugging and experimenting with I2C devices although could be used to drive I2C devices from a PC. In addition to the above there is an ‘inspector’ mode that allows ‘viewing’ of the I2C bus which is useful for debugging existing applications.		Qty:
	Quantity discounts price each 2 £16.90, 10 £14.61, 100 £11.98

This is a device that you can plug into the USB and use it to drive I2C devices, it will also work the other way round and inspect the I2C bus for debugging purposes. This device will enable a standard PC to control, LCD's, Analogue to Digital Converters, Real time Clocks, Temperature Sensors, EEPROM storage etc. In fact any I2C device on the market. This can be done interactively or through a user program.

This site contains a full interactive set of web pages that can be used with this device, see the VBSweb section of this site.

The newer type is fitted with a socket and comes with a 4 way pin head to allow for versatile connectivity. The LED's can be seen in the picture, one indicates the state of the SCL line the other the SDA line. If both are on, the bus is free.

The device has a USB connector at one end and the I2C interface at the other. There are built in pull up resistors to the SDA and SCL line and also LED indicators. The indicators are illuminated when the bus lines are high, thus when both are illuminated the bus is free. This is very useful for detecting 'locked up' devices.

The BV4221 presents itself to the PC as a COM port, this is useful because it can be used with any terminal software, it will work with Windows and Linux.

s 1 and 20 set the memory address as before

r    sends a re-start condition, telling the EEPROM that we now wish to read it. A restart is a start condition followed by the address plus 1 and so 0xA1 will have been sent.

g-3    this gets three bytes from the EEPROM, it will send the appropriate NACK on the last byte to tell the EEPROM no more bytes are required. As can be seen the bytes that were restored are retrieved.

All of the above can of course be done under program control so that an automated system can be implemented, a temperature logger for example. Very little knowledge of electronics is needed as all of the functionality is within the I2C devices.

Free Software

Software is available for driving this device directly from a PC using a browser. Here is a screen shot of just one of the pages for driving the well known PCF8591. Other devices on the web site are:

BV5205-ADC
BV4205-ADC driving an LM35 temperature sensor (with circuits diagrams)
BV4206 - GPIO
BV4218 - LCD + Keypad IC

The software, which is very simple, is all contained within the browser htm file and can also be used for stand alone VBS applications. This is all explained at this page. The whole (quite small) can be downloaded as a zip file and run form your own PC. VBScript will even run in applications such as Excel so it would be possible to have say a data logger interfacing directly with the spreadsheet. The only limitation is that because VBScript is a Microsoft product this particular software will not work on other operating systems.

Features

• I2C up to 400kHz
• User configurable address
• Simple command set for direct interface to LCD module
• Back light output
• Contrast trimmer
• 1,2 and 4 line displays
• 31 character buffer for I2C
• 12 way crosspoint keypad interface
• 16 key keypad buffer
• Extra general purpose pin or interrupt when key available
• Operating voltage 2.0 to 5.5V
• Current <1mA @ 5V