Sunday, July 27, 2008

USART-to-USB converter using FT232BM chip

Hi guys,
here is an easy an popular way to start using USB in your designs without going into learning the complicated USB protocol. This circuit converts normal USART signals from any microcontroller into USB compatible signals which can be directly connected to the PC. If u r designing a circuit and u need pc interface, then this is the best way, use USB, as the RS232 ports are disappearing from PCs and laptops very fast.

This circuit is as suggested by FTDI's datasheet for the device FT232BM. It also includes an EEPROM to input your device name which will appear in PC when u connect your circuit to PC. The Tx and Rx LED indication is also provided.

Drivers for this IC are available free on FTDI's website mentioned below. The drivers create virtual serial comm ports, hence keep the USB protocol completely in background. U can program yr controller just like u r designing it for RS232 communication!!

New! (21 May 2010)

FTDI has released a RS232 to USB converter in DB9 connector package, an easiest way to migrate from RS232 to USB without any change in your PCB, you can have the footprint of DB9 female connector but place this module instead and you are USB ready!! Really cool!!!

More info: http://www.ftdichip.com

Saturday, July 26, 2008

Ring Detector for Caller ID Unit

Hi Friends,
this is an addition to the caller ID circuit of my previous post. For deciding whether call is received call or missed call, u need to monitor the ringing signal along with the off-hook detector signal, which is discussed in the last post. If the off-hook detector signal goes low (i.e. receiver lifted) before the ringing signal stops, then the call is labeled as received call, otherwise it is a missed call.
This small circuit converts the ringing signal (sine wave 90vrms) into 5v dc pulses which can be directly fed to microcontroller pin. The circuit outputs a pulse for each ring. The delay between two pulses is to be monitered and if it exceeds 4 sec, then ring is dead, hence, the call is missed call.!
Try it out..

Friday, July 25, 2008

Design Caller ID using DTMF decoder MT8870

Hi friends,
one more circuit: DTMF decoder interface for designing Caller ID Unit. It's very simple circuit using DTMF decoder MT8870 (or CM8870). As shown in the circuit, u'll receive an interrupt ( if NAND output is connected to INT of the microcontroller) whenever u receive a call or make a call and then u can use yr program to read the digits coming out of pin 11 to 14 of the MT8870. I designed the circuit with additional features like seperating received calls, missed calls, dialled numbers along with telephone directory.

Download datasheet:

To determine whether number is dialled or received, u need to know whether receiver is on-hook or off-hook. following simple circuit will give u that indication:

I had used microcontroller 8951 with16x2 LCD and Dallas nvRAM for storing numbers and names. The code is in assembly language. It's really easy to make this one with lot of variations.

Check out my next post on telephone ring detector to check whether the call is received call or missed call.


Thursday, July 17, 2008

Rate or Position measurement using Solid State Gyroscope


Hi friends,
here is a circuit to measure rate of a rotating object using solid state gyro ADXRS150 (used here is DIP sized evaluation version). this circuit gives output of -10v to +10v for rate upto 80 deg/sec in both the directions (i.e. -80 to +80 deg/sec). A direction o/p logic signal is also there to feed to microcontroller. Temperature of gyroscope also can be measured with onchip ADC of the microcontroller like ATmega32 (describd in previos post), which can be used for temperature compensation of the gyro o/p.

find the detailed datasheet of ADXRS150 here:
ADXRS150 Datasheet

Sunday, July 13, 2008

interfacing ATmega32


Hi techies!! 

This is one more of my circuits, interfacing ATmega32 with an LCD and a DAC. it also includes two general purpose push-buttons and In System Programming connector. The controller is operating with 14.7456 MHz frequency crystal, convenient for gene

rating standard baud rates (for RS422 communication which I used in my actual project, not shown here). The Atmel AVR controller ATmega32 is a very powerful chip with 1 MIPS/MHz throughput and contains a lots of on-chip peripherals like UART, SPI, 32bits I/O, TWI(I2C compatible), versatile timer/counters and lot more.. the LCD and DAC driver functions are written in C(using imageCraft compiler)  

Download schematic & code for LCD interfacing 


Saturday, July 12, 2008

Hi all the techy guys!!! welcome to this blog!
I love designing things with microcontroller,
so here I m, to share the my ideas with you guys and to know your ideas!!
Start Blogging!!!