Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: yash25 on July 07, 2009, 05:47:16 PM

Title: Doubt with the MAX 232.
Post by: yash25 on July 07, 2009, 05:47:16 PM

Okay I was just reading Admin's UART and RS232 tutorial..and he says that the serial port in the PC has a 12 volt supply and thats why we use the MAX 232 ic for converting 5 volts of the controller to 12V of the PC...then why is the ISP cable in the 50$ tutorial directly connected to the serial? without any sort of voltage converting IC?

Title: Re: Doubt with the MAX 232.
Post by: GearMotion on July 07, 2009, 07:06:13 PM

Quote from: yash25 on July 07, 2009, 05:47:16 PM

Okay I was just reading Admin's UART and RS232 tutorial..and he says that the serial port in the PC has a 12 volt supply and thats why we use the MAX 232 ic for converting 5 volts of the controller to 12V of the PC...then why is the ISP cable in the 50$ tutorial directly connected to the serial? without any sort of voltage converting IC?

There are components other than "voltage converting ICs" that will lower the voltage.

Specifically the Zener devices (Z1, Z2) are devices that "regulate" voltage. These are 5.1V Zener diodes. That node of the circuit is prevented from reaching a higher voltage by the property of the Zener.

Title: Re: Doubt with the MAX 232.
Post by: Ro-Bot-X on July 07, 2009, 09:11:32 PM

Almost everything is serial. RS232 is serial, USB is serial, UART is serial, I2S is serial, TWI is serial (different name for I2C), SPI is serial... ISP uses SPI to program the microcontroller so the programmer is serial (and that is the only way for ISP programming). The programmer will connect 2 devices using different serial modes to transfer the data. One device is the microcontroller that uses SPI and the other is the PC that can use the USB port, or the Serial port (RS232) or the paralel port. The programmer will use eighter a dedicated ICs, or tranzistors, or diodes or whatever, to convert the signal from one format to the other. So this is different of the regular serial communication with the PC that requires just the voltage level adjustment. For that, the easiest way to do it is using a MAX232 IC, but you can also use tranzistors. Does it make more sense now?

Title: Re: Doubt with the MAX 232.
Post by: yash25 on July 08, 2009, 02:14:22 AM

Yes I got the reason why we use a MAx232...but then why is'nt this IC being used in the 50$ tutorial?( If I'm not wrong , even that uses serial communication)

Title: Re: Doubt with the MAX 232.
Post by: Ro-Bot-X on July 08, 2009, 05:42:42 AM

Because it's a different type of serial communication.

Title: Re: Doubt with the MAX 232.
Post by: yash25 on July 08, 2009, 08:15:33 AM

thank you!