Electronic – arduino – Cannot connect Arduino Uno REV3 ATmega16u2 serial connection to outside serial connection

arduinoatmegaatmega32u4serialuart

I wanted to simply use the ATmega16u2 on my official Arduino Uno with a serial connection.

I connected my Serial Board (where I can simply connect any serial connection and read it on my PC via Putty) The Board to the Uno and the connection is reliable because it already worked with previous Projects written in the Arduino IDE.

RX -> RX and TX -> TX since the connection for the ATmega16u2 is reversed from the normal pinout as we see in https://content.arduino.cc/assets/UNO-TH_Rev3e_sch.pdf

I also saw that the pin 15/PB1 is free on the icsp and so I connected it to the Arduino pin 13 which is connected to the LED L to have some output.

Now here is my code:

/*
 * Simple_Test1.cpp
 *
 * Created: 20-May-20 17:35:10
 * Author : Paukler
 */ 

#include <avr/io.h>
#include <util/delay.h>

void init_USART(int);
void USART_Transmit( unsigned char data );
void USART_Transmit_wait( unsigned char data );
unsigned char USART_Receive( void );
unsigned char USART_Receive_wait( void );
bool USART_Receive_available( void );

int main(void)
{
    DDRB = 1<<1;//DDRC = 1<<7;
    init_USART(9600);
    PORTB &= (0xff-(1<<1));//PORTC &= (0xff-(1<<7));//led off
    while (1) 
    {
        if(USART_Receive_available()){
            unsigned char in = USART_Receive_wait();
            PORTB |= 1<<1;//PORTC |= 1<<7;//led on
            _delay_ms(1000*5);
            PORTB &= (0xff-(1<<1));//PORTC &= (0xff-(1<<7));//led off
            _delay_ms(1000*5);
            USART_Transmit_wait(in);
            PORTB |= 1<<1;//PORTC |= 1<<7;//led on
            _delay_ms(1000*5);
            PORTB &= (0xff-(1<<1));//PORTC &= (0xff-(1<<7));//led off
        }
        _delay_ms(1000);
    }
}

void init_USART(int baud){
    /* Set baud rate */
    UBRR1H = (unsigned char)(baud>>8);
    UBRR1L = (unsigned char)baud;
    /* Enable receiver and transmitter */
    UCSR1B = (1<<RXEN1)|(1<<TXEN1);
    /* Set frame format: 8data, 2stop bit */
    UCSR1C = (1<<USBS1)|(3<<UCSZ10);
}

void USART_Transmit_wait( unsigned char data )
{
    /* Wait for empty transmit buffer */
    while ( !( UCSR1A & (1<<UDRE1)) )
    ;
    /* Put data into buffer, sends the data */
    UDR1 = data;
}

bool USART_Transmit_available( void ){
    return (1<<UDRE1);
}

void USART_Transmit( unsigned char data )
{
    if ( ( UCSR1A & (1<<UDRE1)) ){
        /* Put data into buffer, sends the data */
        UDR1 = data;
    }
}

unsigned char USART_Receive_wait( void )
{
    /* Wait for data to be received */
    while ( !(UCSR1A & (1<<RXC1)) )
    ;
    /* Get and return received data from buffer */
    return UDR1;
}

bool USART_Receive_available( void ){
    return (1<<RXC1);
}

unsigned char USART_Receive( void )
{
        return UDR1;
}

When I send a '2' or '3', it seems to receive and send something as indicated by the LED, but that doesn't always work. I never however get any data on my serial PC connection.

I also tried playing around with the stop bits, the parity, the flow control, but nothing worked.

I have no idea what I am doing wrong. If somebody could help me, that would be awesome.

The exact same behavior on my Leonardo (where it's only one chip and no reversing etc.) with slightly modified code:

/*
 * Simple_Test1.cpp
 *
 * Created: 20-May-20 17:35:10
 * Author : Paukler
 */ 

#include <avr/io.h>
#include <util/delay.h>

void init_USART(int);
void USART_Transmit( unsigned char data );
void USART_Transmit_wait( unsigned char data );
unsigned char USART_Receive( void );
unsigned char USART_Receive_wait( void );
bool USART_Receive_available( void );

int main(void)
{
    DDRC = 1<<7;//DDRB = 1<<1;
    init_USART(9600);
    PORTC &= (0xff-(1<<7));//led off//PORTB &= (0xff-(1<<1));
    while (1) 
    {
        if(USART_Receive_available()){
            unsigned char in = USART_Receive_wait();
            PORTC |= 1<<7;//PORTB |= 1<<1;//led on
            _delay_ms(1000*5);
            PORTC &= (0xff-(1<<7));//PORTB &= (0xff-(1<<1))//led off
            _delay_ms(1000*5);
            USART_Transmit_wait(in);
            PORTC |= 1<<7;//PORTB |= 1<<1;//led on
            _delay_ms(1000*5);
            PORTC &= (0xff-(1<<7));//PORTB &= (0xff-(1<<1))//led off
        }
        /*PORTC |= 1<<7;//PORTB |= 1<<1;//led on
        _delay_ms(1000);
        PORTC &= (0xff-(1<<7));//led off//PORTB &= (0xff-(1<<1));
        _delay_ms(1000);*/
    }
}

void init_USART(int baud){
    /* Set baud rate */
    UBRR1H = (unsigned char)(baud>>8);
    UBRR1L = (unsigned char)baud;
    /* Enable receiver and transmitter */
    UCSR1B = (1<<RXEN1)|(1<<TXEN1);
    /* Set frame format: 8data, 2stop bit */
    UCSR1C = (1<<USBS1)|(3<<UCSZ10);
}

void USART_Transmit_wait( unsigned char data )
{
    /* Wait for empty transmit buffer */
    while ( !( UCSR1A & (1<<UDRE1)) )
    ;
    /* Put data into buffer, sends the data */
    UDR1 = data;
}

bool USART_Transmit_available( void ){
    return (1<<UDRE1);
}

void USART_Transmit( unsigned char data )
{
    if ( ( UCSR1A & (1<<UDRE1)) ){
        /* Put data into buffer, sends the data */
        UDR1 = data;
    }
}

unsigned char USART_Receive_wait( void )
{
    /* Wait for data to be received */
    while ( !(UCSR1A & (1<<RXC1)) )
    ;
    /* Get and return received data from buffer */
    return UDR1;
}

bool USART_Receive_available( void ){
    return (1<<RXC1);
}

unsigned char USART_Receive( void )
{
        return UDR1;
}

Is my code wrong or am I missing something? It's not urgent since this is just as a hobby, but I would appreciate any help.

@Justme was correct and here is my final code. It works now.

/*
 * Simple_Test1.cpp
 *
 * Created: 20-May-20 17:35:10
 * Author : Paukler
 */ 

#include <avr/io.h>

#ifndef F_CPU
#define F_CPU 16000000L
#endif

#include <util/delay.h>

#define BAUD 9600
#define UBRR_VAL ((( F_CPU / ( BAUD * 16UL))) - 1) // 103 for 16M=F_CPU and BAUD=9600

void init_USART(int);
void USART_Transmit( unsigned char data );
void USART_Transmit_wait( unsigned char data );
unsigned char USART_Receive( void );
unsigned char USART_Receive_wait( void );
bool USART_Receive_available( void );

int main(void)
{
    DDRC = 1<<7;//DDRB = 1<<1;
    init_USART(UBRR_VAL);
    PORTC &= (0xff-(1<<7));//led off//PORTB &= (0xff-(1<<1));
    while (1) 
    {
        if(USART_Receive_available()){
            unsigned char in = USART_Receive_wait();
            PORTC |= 1<<7;//PORTB |= 1<<1;//led on
            _delay_ms(1000);
            PORTC &= (0xff-(1<<7));//PORTB &= (0xff-(1<<1))//led off
            _delay_ms(1000);
            USART_Transmit_wait(in);
            PORTC |= 1<<7;//PORTB |= 1<<1;//led on
            _delay_ms(1000);
            PORTC &= (0xff-(1<<7));//PORTB &= (0xff-(1<<1))//led off
        }
        /*PORTC |= 1<<7;//PORTB |= 1<<1;//led on
        _delay_ms(1000);
        PORTC &= (0xff-(1<<7));//led off//PORTB &= (0xff-(1<<1));
        _delay_ms(1000);*/
    }
}

void init_USART(int baud){
    /* Set baud rate */
    UBRR1H = (unsigned char)(baud>>8);
    UBRR1L = (unsigned char)baud;
    /* Enable receiver and transmitter */
    UCSR1B = (1<<RXEN1)|(1<<TXEN1);
    /* Set frame format: 8data, 2stop bit */
    UCSR1C = (1<<USBS1)|(3<<UCSZ10);
}

void USART_Transmit_wait( unsigned char data )
{
    /* Wait for empty transmit buffer */
    while ( !( UCSR1A & (1<<UDRE1)) )
    ;
    /* Put data into buffer, sends the data */
    UDR1 = data;
}

bool USART_Transmit_available( void ){
    return (1<<UDRE1);
}

void USART_Transmit( unsigned char data )
{
    if ( ( UCSR1A & (1<<UDRE1)) ){
        /* Put data into buffer, sends the data */
        UDR1 = data;
    }
}

unsigned char USART_Receive_wait( void )
{
    /* Wait for data to be received */
    while ( !(UCSR1A & (1<<RXC1)) )
    ;
    /* Get and return received data from buffer */
    return UDR1;
}

bool USART_Receive_available( void ){
    return (1<<RXC1);
}

unsigned char USART_Receive( void )
{
        return UDR1;
}
```

Best Answer

The baud rate is incorrect.

Your code writes the baud rate value directly to the register, that is not how it works.

The AVR runs at some clock frequency, which must be divided by some divisor, to achieve the baud rate. It's the divisor that must be written to the register.

Related Solutions

Electronic – arduino – Connect two Arduinos via simple Serial connection

The RX/TX are the USB connection LEDs. They indicate whether your ATMEGA is transmitting (TX) or receiving data (RX) as opposed to the PC. If you're transmitting data, it's sent to both the USB converter chip and the connected node. After all, the USB chip is sending data to the host PC UART.

If you're receiving data from the connected node, the USB chip hasn't sent the data to the arduino, so no RX LED will be lit. It doesn't mean there is nothing sent though! The ATMEGA may still be receiving data, but the USB chip isn't involved, thus no LED will blink.

In other words, TX means data sent to USB, RX means data received from USB. These LEDs are directly tied to the USB UART converter chip, so you can't change their behaviour.

Having said that, my guess is that your code is probably working fine. If you're unfamiliar to a piece of hardware, don't always trust it! Especially these things can be deceiving if you think that the RX/TX are related to your microcontroller, whereas they are only related to the USB UART chip. Solution: look up schematics, find datasheets and figure out when certain indicators are lit.

Electronic – arduino – Make LUFA for Arduino UNO / atmega16u2

As per my comment, you have specified UNO board, but it doesn't have Keyboard/Joystick required definitions for the board (I'm not sure if UNO has any buttons to be defined there, it only has Leds, and leds are defined in Led.h - check out \LUFA-111009\LUFA\Drivers\Board\AVR8\UNO)

So what you could do is to create Board folder under your KeyboardMouse and make empty files Joystick.h and Buttons.h there. This should get you going further. Errors you are seeing are due to the following code in \LUFA\Drivers\Board\Buttons.h

#if (BOARD == BOARD_NONE)
    #error The Board Buttons driver cannot be used if the makefile BOARD option is not set.
#elif (BOARD == BOARD_USBKEY)
    #include "AVR8/USBKEY/Buttons.h"
....
#else
    #include "Board/Buttons.h" <------ THIS IS EXECUTED SINCE UNO DOES NOT HAVE BUTTONS
#endif

So your error

../../../../LUFA/Drivers/Board/Joystick.h:119:31: error: Board/Joystick.h: No such file or directory

means that your folder structure and your LUFA configuration is correct, but you're missing file Buttons.h in your KeyboardMouse/Board/ folder. Got it?

Try what I've suggested and see how far you get. You can see how to define buttons in other Board's folders, for example in LUFA\Drivers\Board\AVR8\USBKEY\

EDIT Btw, I forgot to mention, error about common.h should go away hopefully after fixing this since that ........\ is coming from a file in a different location in folder structure thus confusion.

EDIT OK, so here's the link on how to build custom board drivers: http://www.fourwalledcubicle.com/files/LUFA/Doc/111009/html/page_writing_board_drivers.html

What you need to do is to copy files Buttons.h and Joystick.h LUFA\CodeTemplates\DriverStubs\ (or try copying Buttons.h and Joystick.h from USBKEY better, I think you still would need to specify a value for each definition otherwise) This should get rid of undefined errors. You have TODO sections in the files that you need to update.

OK, so I think I should also mention how this is supposed to be used before going further. These drivers/definitions are meant to be used in a specific manner in your code, and LUFA is unifying the approach for you. As far as I can tell, buttons are used in a following manner:

if (Buttons_GetStatus() & BUTTONS_BUTTON1){ ... do something when button 1 pressed....

This way, if you have several boards with at least one button, your code should theoretically stay the same across the boards. Similar stands for LEDs, you can use them like:

LEDs_SetAllLEDs(LEDMASK_USB_NOTREADY);
....
LEDs_SetAllLEDs(LEDMASK_USB_ENUMERATING);

I hope you get the picture. In order to use these library functions you have to define buttons/joystick/led specifics in their respective header files. So for example - in buttons.h you need to specify any custom header files you need, add port masks for buttons (on which pin of which port they are connected), specify port initialization and how to read the status of the buttons. You can find all of that in the USBKEY's buttons.h - e.g. it's importing common.h, defines BUTTONS_BUTTON1 like pin 2 of a port, initializes PortE with this button (so button is pin 2 on port E), and in Buttons_GetStatus it reads the status of the button.

I could go on and on in the same manner for joystick as well, but I hope you get the picture. Joystick is more involved but it's like having 4 buttons of which 0, 1 or 2 can be active at any time.

BTW, this is only useful if you have any buttons on your board. For example, I made keyboard driver without any buttons (I had to remove buttons specific code though). I used Ir Diode to read remote control codes and make the board act as keyboard. So you don't really need the buttons, nor the joystick (of course, it completely depends on what you're doing).

Best Answer

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