Okay guys I am new to the mbed world , but I have fairly good knowledge in C/C++ and EE.
I want to make the multimeter with LPC1768 uC.
So first I made a capacititance meter but I had problem with discharging the capacitor , I tried to add a BC547 BJT transistor to act as a switch and making PIN5 low when BJT is active so capacitor can discharge via resistor in connected to the emitter of BJT and to the GND.
[url=https://postimg.org/image/wtlbac7nl/][img]https://s32.postimg.org/wtlbac7nl/capacitance_meter.jpg[/img][/url]
But capacitor would never fully discharge , so I googled and found out this thread https://developer.mbed.org/forum/electronics/topic/2783/
So basically copied the discharge solution from the link above and capacitormeter works up to some accuracy level.
But I am not really familiar with the DigitalInOut class , so if someone could provide me with some link with explanations what happens when each function is called and I don't mean on explanation of the functions like on this link , but what happens with the inner circuit of the uC:
https://developer.mbed.org/handbook/DigitalInOut they are pretty clear.
When we call for example a function dischargePin.input() , what happens with inner circuit of a uC , I know each pin has a transistor and resistor built in , so when we declare a pin as an input it pulls pin into low impedance state making the current to flow into the pin, or the opposite for the dischargePin.output() if I am not mistaken?
So if anyone has some good link to provide on explaining digital I/O modes and uC behaviour or to explain in short here?
This is the code and the circuit:
[code]
- include "mbed.h"
void discharge(void);
AnalogIn ain(p20);
DigitalOut chargePin(p5);
DigitalInOut dischargePin(p6);
Serial pc(USBTX, USBRX);
Timer timer;
double averageCapacitance = 0;
int i = 0;
const double resistor = 99100;
double timeConstant;
double capacitance;
int main() {
while(1){
if( i == 10){
pc.printf("Average capacitance is %f uF\n\r", averageCapacitance/i);
i = 0;
}
chargePin = 0;
dischargePin.output();
dischargePin = 0;
while(ain.read() > 0 ){}
timer.reset();
dischargePin.input();
dischargePin.mode(PullNone);
pc.printf("Capacitance meter\n\r");
char buttonPressed = pc.getc();
if(buttonPressed == '1'){
chargePin = 1;
timer.start();
while(1){
if(ain.read() >= 0.63212){
timer.stop();
timeConstant = timer.read_us();
timer.reset();
capacitance = (timeConstant/ resistor);
pc.printf("Capacitance: %f uF\n\r", capacitance);
averageCapacitance += capacitance;
i++;
break;
}
}
}
}
}
void discharge(){
chargePin = 0;
dischargePin.output();
dischargePin = 0;
while(ain.read() > 0){}
dischargePin = 0;
pc.printf("Discharge has finished!\n\r");
}
[/code]
[url=https://postimg.org/image/w07ec0xkn/][img]https://s31.postimg.org/52dhaacxn/capat_meter_2.jpg[/img][/url][url=https://postimage.org/]free pic[/url]
Also off topic I would like to know if there is option for mbed IDE to make curly braces highlighted when we select them with the mouse , because I get lost sometimes with this IDE.
Ivan Antunović.
0
replies
Okay guys I am new to the mbed world , but I have fairly good knowledge in C/C++ and EE. I want to make the multimeter with LPC1768 uC.
So first I made a capacititance meter but I had problem with discharging the capacitor , I tried to add a BC547 BJT transistor to act as a switch and making PIN5 low when BJT is active so capacitor can discharge via resistor in connected to the emitter of BJT and to the GND. [url=https://postimg.org/image/wtlbac7nl/][img]https://s32.postimg.org/wtlbac7nl/capacitance_meter.jpg[/img][/url]
But capacitor would never fully discharge , so I googled and found out this thread https://developer.mbed.org/forum/electronics/topic/2783/
So basically copied the discharge solution from the link above and capacitormeter works up to some accuracy level.
But I am not really familiar with the DigitalInOut class , so if someone could provide me with some link with explanations what happens when each function is called and I don't mean on explanation of the functions like on this link , but what happens with the inner circuit of the uC: https://developer.mbed.org/handbook/DigitalInOut they are pretty clear.
When we call for example a function dischargePin.input() , what happens with inner circuit of a uC , I know each pin has a transistor and resistor built in , so when we declare a pin as an input it pulls pin into low impedance state making the current to flow into the pin, or the opposite for the dischargePin.output() if I am not mistaken?
So if anyone has some good link to provide on explaining digital I/O modes and uC behaviour or to explain in short here?
This is the code and the circuit: [code]
void discharge(void);
AnalogIn ain(p20); DigitalOut chargePin(p5); DigitalInOut dischargePin(p6);
Serial pc(USBTX, USBRX); Timer timer;
double averageCapacitance = 0; int i = 0; const double resistor = 99100; double timeConstant; double capacitance;
int main() {
while(1){
if( i == 10){ pc.printf("Average capacitance is %f uF\n\r", averageCapacitance/i); i = 0; } chargePin = 0; dischargePin.output(); dischargePin = 0; while(ain.read() > 0 ){}
timer.reset();
dischargePin.input(); dischargePin.mode(PullNone);
pc.printf("Capacitance meter\n\r");
char buttonPressed = pc.getc();
if(buttonPressed == '1'){
chargePin = 1; timer.start();
while(1){ if(ain.read() >= 0.63212){
timer.stop(); timeConstant = timer.read_us(); timer.reset(); capacitance = (timeConstant/ resistor); pc.printf("Capacitance: %f uF\n\r", capacitance); averageCapacitance += capacitance; i++; break; } } } } } void discharge(){
chargePin = 0; dischargePin.output(); dischargePin = 0; while(ain.read() > 0){} dischargePin = 0; pc.printf("Discharge has finished!\n\r"); } [/code]
[url=https://postimg.org/image/w07ec0xkn/][img]https://s31.postimg.org/52dhaacxn/capat_meter_2.jpg[/img][/url][url=https://postimage.org/]free pic[/url]
Also off topic I would like to know if there is option for mbed IDE to make curly braces highlighted when we select them with the mouse , because I get lost sometimes with this IDE.