TFT displaying odd characters - Updated

Projects Programming
1

I have successfully managed to send various messages from one Arduino to another. I have set up one with four buttons and a an RF transmitter. I'm using the Virtual Wire library. When an individual button is pressed, the RF receiver on the second Arduino displays the message in it's Serial Monitor. I want this message also appear on a TFT that is also attached to the second Arduino. The problem is that the TFT displays odd characters.

For instance, if I send the message "Message 1", the TFT displays y 1/4 1/2 1/2 a N W h
If I send "Message 2", the TFT displays y 1/4 1/2 1/2 a N W i

Obviously y = M, 1/4 = e, 1/2 = s ...and so on

***There's a letter missing in each of the example above, I think it corresponds to the 5th character. I'll check when I get a chance tomorrow)

(The fractions above are one character each and the N has a line above it).

The code to print to the Serial Monitor is
Serial.print((char )buf*);*
The code to print to the TFT is
tft.print(((char )buf*), ST7735_WHITE);*
Any help would be appreciated

2

Forget about messages coming from the other Arduino for now, can you print strings to the TFT display from the Arduino that it is connected to ?

3

Hi

I've modified the post. Yes, I can print strings to the TFT

4

The code to print to the Serial Monitor is
Serial.print((char )buf);

The code to print to the TFT is
tft.print(((char )buf), ST7735_WHITE);

What type is buf? Why do you need to cast to char? To char * might make sense. To char does not.

Where is the rest of your code? http://snippets-r-us.com is down the road a ways.

5

Hi Paul

Thanks for posting.

I am getting the message from an RF receiver and successfully seeing this via the Serial Monitor. Here is the loop code

void loop()
{
  
    tft.fillScreen(ST7735_BLACK);
    tft.setTextSize(2);
    tft.setCursor(10, 20);
    tft.setTextWrap(true);

    uint8_t buf[VW_MAX_MESSAGE_LEN];
    uint8_t buflen = VW_MAX_MESSAGE_LEN;
  
    if (vw_get_message(buf, &buflen)) 
    {
    int i;
    char msg;

    for (i = 0; i < buflen; i++)
	{
    tft.print(((char )buf[i]), ST7735_WHITE);
    Serial.print((char )buf[i]);
    }
    Serial.println(""); 
    delay (10000);
 }
}
6

I don't understand why you
A) Can't post ALL of your code
B) Don't NULL terminate the array and use it as a string
C) Use Tools + Auto Format to fix your horrid indenting

    if (vw_get_message(buf, &buflen)) 
    {
       buf[buflen] = '\0';
       tft.print(buf, ST7735_WHITE);
       Serial.print(buf);
    }

Some casting may be required, depending on how buf is defined.

7

Hi

I don't have access to the actual code until later; I have it in text format (Notepad file). Here it is

#define sclk 13
#define mosi 11
#define cs   10
#define dc   9
#define rst  8


#include <VirtualWire.h>
#include <Adafruit_GFX.h>    
#include <Adafruit_ST7735.h>
#include <SPI.h>
#include <VirtualWire.h>

Adafruit_ST7735 tft = Adafruit_ST7735(cs, dc, rst);
float p = 3.1415926;


void setup()
{
    tft.initR(INITR_BLACKTAB);
  
    Serial.begin(9600);
  
    vw_set_rx_pin(7);           
    vw_set_ptt_inverted(true); 
    vw_setup(2000);	 
    vw_rx_start();      
}


void loop()
{
  
    tft.fillScreen(ST7735_BLACK);
    tft.setTextSize(2);
    tft.setCursor(10, 20);
    tft.setTextWrap(true);

    uint8_t buf[VW_MAX_MESSAGE_LEN];
    uint8_t buflen = VW_MAX_MESSAGE_LEN;
  
    if (vw_get_message(buf, &buflen)) 
    {
    int i;
    char msg;

    for (i = 0; i < buflen; i++)
	{
    tft.print(((char )buf[i]), ST7735_WHITE);
    Serial.print((char )buf[i]);
    }
    Serial.println(""); 
    delay (10000);
 }
}
8

Paul

Apologies for the delay (I've not been able to get online). Your suggestion of using char * worked like a dream.

Thanks again

Rob