Atmega328P FTDI 5V USB Serial Communication

atmegacommunicationserialusb

I am working a Atmega328P and FTDI 5V USB Cable to get a Serial Communication between the Micro-controller and the PC. I am using Tera Term for receiving out from Micro-controller.

I am using an FTDI 5V USB Cable with 6 pinout.

I have following connections as

FTDI——->ATmega328P
VCC——–>Power
GND——->Ground
RX———>Pin3

I am using the following code:

int main(void)
{

    UBRR0H = (BRC >> 8);
    UBRR0L = BRC;

    UCSR0B = (1 << TXEN0);
    UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);

    while(1)
    {
        UDR0 = '8';
        _delay_ms(1000);

    }
}

But I am not getting any values back in my Tera Term screen. I have done the appropriate settings with my Tera Term for serial.
I am kind of stuck with this for sometime now. Please can someone let me know, if I am doing something wrong?

Best Answer

You probably need to get an oscilloscope involved so that you can see signal levels and whether any actual serial signals are appearing.

Do know that the number one mistake made in connecting up serial ports like this is getting the Tx and Rx signals cross wired. The FTDI cable will be labeled with Tx being its output signal pin on pin 4 (orange wire) and its Rx being its input signal on pin 5 (yellow wire).

enter image description here

You must connect the Tx pin of the FTDI cable to the Rx pin on the AVR. Likewise you must connect the Tx pin of the FTDI cable to the Tx pin on the AVR.

The big mistake that is often made is that folks connect the two Tx signals together and the two Rx signals together.

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You can definitely transmit data using just TX & GND.

Firstly, you want to hook up the ATtiny85 TX line to the FTDI RX line (yellow on the TTL-232R). Make sure that the USB adapter can handle 5V - I'm fairly sure even the 3.3V TTL-232R is 5V tolerant.

According to the example page for SoftwareSerial, you need to set the direction of the TX & RX lines in your setup function:

// include the SoftwareSerial library so you can use its functions:
#include <SoftwareSerial.h>

#define rxPin 2
#define txPin 3
#define ledPin 13

// set up a new serial port
SoftwareSerial mySerial =  SoftwareSerial(rxPin, txPin);
byte pinState = 0;

void setup()  {
  // define pin modes for tx, rx, led pins:
  pinMode(rxPin, INPUT);
  pinMode(txPin, OUTPUT);
  pinMode(ledPin, OUTPUT);
  // set the data rate for the SoftwareSerial port
  mySerial.begin(9600);
}

The baudrate will be 4800 in your case. The SoftwareSerial library doesn't seem to support CTS & RTS, so just make sure you aren't using them on the host software.

Check out the reference page for more details, where they talk about some potential timing issues which may be exacerbated if you're running at 1MHz using the internal oscillator on the tiny.

Electronic – “USB is also a serial communication method” is this true

Most wired communication nowadyas is serial, and so is USB. Serial just means that bits are transferred one after another in time, so that you only need one wire (two if you want to do it differential, like in USB). Expensive term: Time Division Multiplex, compared to Space Division Multiplex, where different bits use different physical wires in parallel. Remember the old IDE hard disks, floppy drives and SCSI devices for instance and the flat cables they used.

enter image description here

Serial has the advantage of smaller and cheaper connectors and cable, but needs a much higher bandwidth than parallel. Nevertheless at high speeds also parallel communication may be timing sensitive if there are delay differences between the different lines, so that all signals may not arrive simultaneously.

Best Answer

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