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Skriven av Krister Karlsson

Kategori: News

Publicerad 06 november 2017

Träffar: 7496

This article shows two code samples. 

The first shows the code run by an Trinket acting as a volt meter. 

The measured value is keyed out on the USB port of the trinket to a host.

Before printing the value to USB the reading is multiplied with a factor so that actual voltage is represented in clear text. 

The Pyton script in the end of the article is suitable to run on a Raspberry Pi in order to receive the keyed values and store them in a file named volt

 

 Video shows the Trinket measuring voltage and keying the result to Windows emulating a USB keyboard. The two resistors divides the input voltage as the measured voltage is higher than the trinket can handle.

 

#include <Keyboard.h>

/*
TrinketKeyboard example
For Trinket by Adafruit Industries
*/

#include <TrinketKeyboard.h>
#include <math.h>

 

#define PIN_BUTTON_CAPITAL_A 0
#define PIN_BUTTON_STRING 2
int sensorPin = 1; // select the input pin for the potentiometer
int sensorValue =0;
int led = 1;

int x = 0;
int y = 0;
long z = 0;
int w = 0;
long v = 0;
long l = 0;
void setup()
{
// button pins as inputs
pinMode(PIN_BUTTON_CAPITAL_A, INPUT);
pinMode(PIN_BUTTON_STRING, INPUT);

// setting input pins to high means turning on internal pull-up resistors
digitalWrite(PIN_BUTTON_CAPITAL_A, HIGH);
digitalWrite(PIN_BUTTON_STRING, HIGH);
pinMode(2,INPUT);
// remember, the buttons are active-low, they read LOW when they are not pressed

// start USB stuff
TrinketKeyboard.begin();
}

void loop()
{
// the poll function must be called at least once every 10 ms
// or cause a keystroke
// if it is not, then the computer may think that the device
// has stopped working, and give errors
TrinketKeyboard.poll();
digitalWrite(led, LOW);
delay(10);

x= x+1;

if (x > 20)
{
y=y+1;
w = analogRead(sensorPin);

z = w + z;
if (y > 700)
{
digitalWrite(led, HIGH);
v = z / y;

l = (1024 – v);

//if (digitalRead(PIN_BUTTON_CAPITAL_A) == LOW)
// 1
// t4his should type a capital A
//Tri.9nketKeyboard.pressKey(KEYCODE_MOD_LEFT_SHIFT, KEYCODE_A);
// this4
// releases the key (otherwise it is held down!)
//TrinketKeyboard.pressKey(0, 0);
//}

//if (digitalRead(PIN_BUTTON_STRING) == LOW)
//{
// type out a string using the Print class
sensorValue = analogRead(sensorPin);
// TrinketKeyboard.print(”Hello World!”);
TrinketKeyboard.print(”Value ”);
TrinketKeyboard.print(sensorValue*0.0117);
TrinketKeyboard.print(”\n”);
y=0;
z=0;
x=0;

}
x=0;
}

// delay(20000);
//Hello World!Hello World!Hello World!Hello World!Hello World! }
}

 

In the raspberry a small python script recives the USB data

import sys
readout=””
fp = open(‘/dev/hidraw0’, ‘rb’)

while True:
buffer = fp.read(8)
for c in buffer:
if ord(c) > 0:
if ord(c) == 30:
readout = readout + ”1”
if ord(c) == 31:
readout = readout + ”2”
if ord(c) == 32:
readout = readout + ”3”
if ord(c) == 33:
readout = readout + ”4”
if ord(c) == 34:
readout = readout + ”5”
if ord(c) == 35:
readout = readout + ”6”
if ord(c) == 36:
readout = readout + ”7”
if ord(c) == 37:
readout = readout + ”8”
if ord(c) == 38:
readout = readout + ”9”
if ord(c) == 39:
readout = readout + ”0”
if ord(c) == 55:
readout = readout + ”.”
if ord(c) == 44:
print readout
f= open(‘/home/pi/volt’, ‘w’)
f.write(readout)
f.close
readout=””

#print ord(c)
#print ”\n”