Newbe needing help with fixed string length

Question

im trying to build a bit of test equipment that will talk to some software and it needs to send a fix string. when the voltage changes the string length does as well. i need to cap the results to 4 in length. (sorry for not knowing the correct terminology. this is the output i need - Where,

X = Flag CP Value
_ = Space
P = Polarity
C = CP Received value
Y = Flag Field Gradient
F = Field Gradient Received value
Z = Flag Contact CP
T = Contact CP Received value

There is also a line feed and carriage return present at the end of each string. The polarity indicator will only display a minus sign ‘-‘ if the received value is negative otherwise no assignation will be transmitted. Although the overall string length is constant the values for each measurement are right justified and hence a space will be present should the value of the measurement not necessitate the utilisation of all allocated character spaces. Sample Outputs

< X -89 Y -1989 Z -1096 >
< X 1039 Y 8 Z 78 >

this is my code so far

#include <Wire.h>
#include <Adafruit_ADS1015.h>
Adafruit_ADS1115 ads1(0x48); // Use this for the 16-bit version
Adafruit_ADS1115 ads2(0x49);
void setup(void) {
 Serial.begin(9600);
 ads1.setGain(GAIN_ONE); // 1x gain +/- 4.096V 1 bit = 2mV 
 ads2.setGain(GAIN_ONE); // 1x gain +/- 4.096V 1 bit = 2mV 
 ads1.begin();
 ads2.begin();
}
void loop(void) {
 int16_t results01,results02,results03;
 results01 = ads1.readADC_Differential_0_1();
 results02 = ads1.readADC_Differential_2_3();
 results03 = ads2.readADC_Differential_0_1();
 Serial.print("X "); 
 Serial.print(round(results01 * multiplier));
 Serial.print(" Y "); 
 Serial.print(round(results02 * multiplier)); 
 Serial.print(" Z "); 
 Serial.print(round(results03 * multiplier));
 Serial.println(); // send a cr/lf
 delay(500);
}

Any help pointing me in the right direction would be Amazing. Thanks in advance

Joe

• JRobert: What is it that your trying to "cap to 4 in length"? I'm assuming you have no control over how the device sends its string, and that you want to format the device's results for the terminal? Can you show a sample of what you want the end-result to look like?
• Joe Lord: < X -89 Y -1989 Z -1096 >
• Joe Lord: each of the reading im getting need to be 4 in length . im reading -2000 to +2000 but say when the voltage is -89 it shortens the string.
• JRobert: So you want to print, e.g. "15" as "0015"? How about "-1500"? How can that take fewer than 5 printing characters?
• Joe Lord: sorry i mean 5 characters. "___15" or " __-15" or "-1500" or "_1500" like i said im very new to this and im amazed i have got this far without asking for help . :)

Answer 1

The printf() family of functions comes handy when you need this kind of control over the formatted output:

/*
 * Format a number as 5 characters.
 * Returns the string in a statically allocated buffer.
 */
char * format5(int x)
{
 static char buffer[6]; // 5 chars + terminating NUL
 snprintf(buffer, sizeof buffer, "%5d", x);
 return buffer;
}
void setup() {
 Serial.begin(9600);
 Serial.println(format5(15));
 Serial.println(format5(-15));
 Serial.println(format5(-1500));
 Serial.println(format5(1500));
}
void loop(){}

output:

 15
 -15
-1500
 1500

• Joe Lord: thanks for this. as been very new to this I have tried and cant get this working...