How to choose the Arduino MCU for fast and double precision data
processing
Giovanni Carrera, 19/02/2025
In my case I had to convert in real time the
coordinates of a GNSS RTK receiver from degrees and minutes to degrees with at
least 7-8 decimal places to have a resolution lower than a centimeter. So it
was necessary to use double precision calculations. To do this I initially used
an Arduino Due board with a program developed with Arduino IDE. Then I used
other 32-bit MCUs because the 8-bit ones accept double precision but do the
calculations in single. I also discarded the development in MicroPython because,
at the moment, it uses single precision.
I then wrote the following program and, with
minor modifications (serial UART), ran it on several 32-bit MCUs. All of the
ones listed here gave identical results, but with very different execution
times.
The program is as follows:
/* program
doubletest.ino
test double precision of MCU
Giovanni Carrera, 14/10/2019*/
const String Lats = "4221.0081996";
const String Longs =
"01321.4740622";
void setup(void) {
Serial.begin(115200);
while (!Serial) {
; // wait for serial port to connect
}
delay(100);
Serial.println("MCU double precision
test");
// convert Lat&Long in decimal format
unsigned long
ti= micros();
String minuts = Lats.substring(2);// latitude
minutes
double minutes = minuts.toFloat();// convert
it to float
double decdeg = minutes/60.0;
String Latdegs = Lats.substring(0,2);
double Latd = Latdegs.toFloat() + decdeg;//
latitude in decimal format (double)
minuts = Longs.substring(3);// longitude
minutes
minutes = minuts.toFloat();// convert it to
float
decdeg = minutes/60.0;
String Longdegs = Longs.substring(0,3);
double Longd = Longdegs.toFloat() + decdeg;//
longitude in decimal format (double)
unsigned long
tf= micros();
Serial.print("Latitude (dec) = ");
Serial.println(Latd,8);
Serial.print("Longitude (dec) = ");
Serial.println(Longd,8);
Serial.print("elaboration time [us] =
");
Serial.println(tf-ti);
} // end of setup
void loop() {
}
The following table summarizes the results of
my tests.
|
board |
MCU |
CPU
clock [MHz] |
time
[µs] |
|
Teensy 4.0 |
ARM Cortex-M7 |
600 |
5 |
|
STM32F401CC |
ARM®Cortex®-M4 |
84 |
102 |
|
Arduino Due |
Atmel SAM3X8E ARM Cortex-M3 |
84 |
141 |
|
ESP32 WROOM |
Xtensa single-/dual-core 32-bit LX6 |
240 |
152 |
|
STM32F103C8T6 |
ARM Cortex-M3 |
72 |
157 |
|
Arduino Uno R4 |
ARM Cortex-M4 |
48 |
184 |
|
Arduino Zero |
ATSAMD21G18 |
48 |
250 |
|
Wemos D1 mini |
ESP8266EX, Tensilica L106 |
80 |
388 |
The graphic representation of the figure shows the differences better.
 |
