QI wireless charger / tester for a Li-Ion battery

LiPo battery "test & charge". A useful COMPONENT to insert in any of your miniaturized projects.

Apr 8, 2022

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energy efficiency

smart appliances

data collection

Components and supplies

QI wireless 5W Coil Circuit Board Module

Through Hole Resistor, 680 kohm

OLED I2C SSD1306 0.96 pollici Display 128 x 64 Pixel (AZDelivery)

Li-Ion 3.7V 250mAh battery

Through Hole Resistor, 220 kohm

Microcontroller PRO Mini w/Atmel AVR ATMEGA328P, 3.3V 8MHz

FT232RL USB to serial TTL (3.3V - 5V) (AZDelivery)

TP4056 Micro USB 5V 1A Li - Ion Battery Charger Module (AZDelivery)

Arduino UNO

Tools and machines

Solder Wire, Lead Free

Soldering iron (generic)

Solder Paste, Tack Flux

Apps and platforms

Arduino IDE

Project description

Code

TEST Sketch on Arduino UNO

c_cpp

Breadboard and Arduino UNO test

1// Charger Wireless QI "snippet" by F.Stella 20220314
2
3#include  <SPI.h>
4#include <Wire.h>
5#include <Adafruit_GFX.h>
6#include <Adafruit_SSD1306.h>
7#include  <Fonts/FreeMono9pt7b.h>
8#include <Fonts/FreeMonoBold9pt7b.h>
9#include <Fonts/FreeMonoBold18pt7b.h>
10//  #include <Fonts/FreeMonoBold24pt7b.h>	
11
12#define SCREEN_WIDTH 128 // OLED  display width, in pixels
13#define SCREEN_HEIGHT 64 // OLED display height, in  pixels
14
15#define debug0      //attiva stampa DEBUG base e SERIAL
16#define  debug1      //attiva stampa DEBUG sezione1
17
18// Declaration for an SSD1306  display connected to I2C (SDA, SCL pins)
19#define OLED_RESET     4 // Reset pin  # (or -1 if sharing Arduino reset pin)
20Adafruit_SSD1306 display(SCREEN_WIDTH,  SCREEN_HEIGHT, &Wire, OLED_RESET);
21
22
23// 'BatteryLevels_bitmap_12x22', 22x12px
24const  unsigned char BatteryLevelFULL [] PROGMEM = {
25	0x1f, 0xff, 0xfc, 0x1f, 0xff,  0xfc, 0x18, 0x00, 0x0c, 0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0xfb, 
26	0xff, 0xec,  0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0x18, 0x00, 0x0c, 0x1f, 0xff,  
27	0xfc, 0x1f, 0xff, 0xfc
28};
29
30const unsigned char BatteryLevelMID []  PROGMEM = {
31	0x1f, 0xff, 0xfc, 0x1f, 0xff, 0xfc, 0x18, 0x00, 0x0c, 0xf8, 0x3f,  0xec, 0xf8, 0x3f, 0xec, 0xf8, 
32	0x3f, 0xec, 0xf8, 0x3f, 0xec, 0xf8, 0x3f, 0xec,  0xf8, 0x3f, 0xec, 0x18, 0x00, 0x0c, 0x1f, 0xff, 
33	0xfc, 0x1f, 0xff, 0xfc
34};
35
36const  unsigned char BatteryLevelEMPTY [] PROGMEM = {
37	0x1f, 0xff, 0xfc, 0x1f, 0xff,  0xfc, 0x18, 0x00, 0x0c, 0xf8, 0x00, 0xcc, 0xf8, 0x00, 0xcc, 0xf8, 
38	0x00, 0xcc,  0xf8, 0x00, 0xcc, 0xf8, 0x00, 0x0c, 0xf8, 0x00, 0xcc, 0x18, 0x00, 0x0c, 0x1f, 0xff,  
39	0xfc, 0x1f, 0xff, 0xfc
40};
41
42byte pin_A     = 2;
43byte button_A  =  0;
44
45int offset18_x = -2;
46int offset18_y = 22;
47int offset12_x = -2;
48int  offset12_y = 14;
49int offset9_x = -1;
50int offset9_y = 12;        
51
52unsigned  long button_delay_t = 0;
53
54int analoginput = 0;            // Battery CHECK  analog pin
55int analogamount = 0;           // stores incoming value
56float  percAREF = 0;
57float percBatt = 0;             // used to store our BATTERY percentage  charge value
58float voltBatt = 0;       
59float voltage = 0;              //  used to store voltage value
60float V_out = 0; 
61float V_source = 0; 
62float  referenceVoltage = 0;
63int voltageError = 0;
64// float resist1 = 4604;        //  4604 tester value 4.7 kOhm nominal - TEST on ARDUINOuno 5V
65// float resist2 =  1000;        //                   1 kOhm nominal  - TEST on ARDUINOuno 5V
66float  resist1 = 982000;         //   1 MOhm  680 kOhm nominal
67float resist2 = 306000;         // 300 kOhm  220 kOhm nominal
68
69void setup() {
70
71#ifdef debug0
72  Serial.begin(19200);
73  Serial.println(F(""));
74  Serial.print(F("Serial  START - press button!"));
75  Serial.println(F(""));
76#endif
77
78  analogReference(INTERNAL);  // use INTERNAL (1.1V) for reference voltage
79
80  display.begin(SSD1306_SWITCHCAPVCC,  0x3C);
81  display.clearDisplay();
82  display.setTextColor(WHITE);
83  display.setFont(&FreeMono9pt7b);                        // PLAIN font
84
85  display.setCursor(1, 10);
86  display.print("Display  on.");
87  display.setCursor(25, 30);
88  display.print("press"); 
89  display.setCursor(15,  50);
90  display.print("to test");
91  display.display();
92
93  pinMode(pin_A,  INPUT_PULLUP);   //button
94}
95
96void loop() {
97  do {
98      button_A  = digitalRead(pin_A);
99  } while ((button_A == 1) || ((millis()-button_delay_t)  < 500));
100
101  button_delay_t = millis();
102
103  #ifdef debug1
104    Serial.print(F("Button  A ("));
105    Serial.print(pin_A); 
106    Serial.print(F(") = ")); 
107    Serial.println(button_A);  
108  #endif
109  batteryCheck();
110  showSCREEN();
111}
112
113void showSCREEN()  {
114  display.clearDisplay();
115  display.setTextColor(WHITE);
116  display.setCursor(10+offset18_x,  20+offset18_y);
117  display.setFont(&FreeMonoBold18pt7b);                        //  PLAIN font
118  display.print(voltBatt,1);
119  display.setCursor(85+offset18_x,  20+offset18_y);
120  display.print("V");
121
122  // display footer ***
123  display.setCursor(47+offset9_x,  51+offset9_y);
124  display.setFont(&FreeMono9pt7b);                        // PLAIN  font
125  display.print(percBatt,1);
126  display.print("%");
127
128  if (percBatt  > 76 ) {                               // Battery level graphic display
129    display.drawBitmap(0,  53, BatteryLevelFULL, 22, 12, WHITE);
130  } else if (percBatt > 65 ) { 
131      display.drawBitmap(0,  53, BatteryLevelMID, 22, 12, WHITE);
132  } else { 
133      display.drawBitmap(0,  53, BatteryLevelEMPTY, 22, 12, WHITE);
134  }  
135  display.display();          //Send  buffer to display
136  delay(3000);
137
138}
139
140void batteryCheck() {
141  referenceVoltage  = 1100;    // 1100 internal;
142  V_source = 4.2;            // LiPo Vmax 4.2V -  UNO R3 5.056 - Vs from the divider calculation
143  // using the REAL resistor values  makes it more "precise" - one can also set a fixed value
144  V_out =  V_source*(resist2)/((resist1)+(resist2));              // UNO 0.889 - LiPo 1.05      - VOut from the divider calculation
145  voltageError = 0;          // to empirically adjust ;-)
146
147  analogamount  = analogRead(analoginput);
148  percAREF=(analogamount/1024.00)*100;
149
150  voltage=(analogamount/1024.00)*referenceVoltage+voltageError;       // in millivolts
151  voltBatt=(voltage*((resist1)+(resist2))/(resist2))/1000;            // V_s = V_out * (R1+R2) / R2
152  percBatt=(voltBatt/V_source)*100;
153
154  #ifdef debug1
155    Serial.print("V_out: ");
156    Serial.println(V_out,3);  
157    Serial.print("Lettura analog (0-1023): ");
158    Serial.print(analogamount);
159    Serial.print(" --------       % of AREF: ");
160    Serial.print(percAREF,2);
161    Serial.print(" --------       A0 (mV): ");   // compare with result of Voltage  Divider calculation Vout
162    // for 5.056 (that I checked on Arduino1) and resistors  1K 4.7K is 0.889
163    Serial.print(voltage,2);
164
165    Serial.print(" --------       % of battery nominal: ");
166    Serial.print(percBatt,2);
167    Serial.print("  --------     Real - no divider (V): "); // if you check Arduino voltage should  be 5.0x
168    Serial.println(voltBatt,2);
169    Serial.println("");
170  #endif
171}
172

// Charger Wireless QI "snippet" by F.Stella 20220314

#include  <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include  <Fonts/FreeMono9pt7b.h>
#include <Fonts/FreeMonoBold9pt7b.h>
#include <Fonts/FreeMonoBold18pt7b.h>
//  #include <Fonts/FreeMonoBold24pt7b.h>	

#define SCREEN_WIDTH 128 // OLED  display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in  pixels

#define debug0      //attiva stampa DEBUG base e SERIAL
#define  debug1      //attiva stampa DEBUG sezione1

// Declaration for an SSD1306  display connected to I2C (SDA, SCL pins)
#define OLED_RESET     4 // Reset pin  # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH,  SCREEN_HEIGHT, &Wire, OLED_RESET);


// 'BatteryLevels_bitmap_12x22', 22x12px
const  unsigned char BatteryLevelFULL [] PROGMEM = {
	0x1f, 0xff, 0xfc, 0x1f, 0xff,  0xfc, 0x18, 0x00, 0x0c, 0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0xfb, 
	0xff, 0xec,  0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0x18, 0x00, 0x0c, 0x1f, 0xff,  
	0xfc, 0x1f, 0xff, 0xfc
};

const unsigned char BatteryLevelMID []  PROGMEM = {
	0x1f, 0xff, 0xfc, 0x1f, 0xff, 0xfc, 0x18, 0x00, 0x0c, 0xf8, 0x3f,  0xec, 0xf8, 0x3f, 0xec, 0xf8, 
	0x3f, 0xec, 0xf8, 0x3f, 0xec, 0xf8, 0x3f, 0xec,  0xf8, 0x3f, 0xec, 0x18, 0x00, 0x0c, 0x1f, 0xff, 
	0xfc, 0x1f, 0xff, 0xfc
};

const  unsigned char BatteryLevelEMPTY [] PROGMEM = {
	0x1f, 0xff, 0xfc, 0x1f, 0xff,  0xfc, 0x18, 0x00, 0x0c, 0xf8, 0x00, 0xcc, 0xf8, 0x00, 0xcc, 0xf8, 
	0x00, 0xcc,  0xf8, 0x00, 0xcc, 0xf8, 0x00, 0x0c, 0xf8, 0x00, 0xcc, 0x18, 0x00, 0x0c, 0x1f, 0xff,  
	0xfc, 0x1f, 0xff, 0xfc
};

byte pin_A     = 2;
byte button_A  =  0;

int offset18_x = -2;
int offset18_y = 22;
int offset12_x = -2;
int  offset12_y = 14;
int offset9_x = -1;
int offset9_y = 12;        

unsigned  long button_delay_t = 0;

int analoginput = 0;            // Battery CHECK  analog pin
int analogamount = 0;           // stores incoming value
float  percAREF = 0;
float percBatt = 0;             // used to store our BATTERY percentage  charge value
float voltBatt = 0;       
float voltage = 0;              //  used to store voltage value
float V_out = 0; 
float V_source = 0; 
float  referenceVoltage = 0;
int voltageError = 0;
// float resist1 = 4604;        //  4604 tester value 4.7 kOhm nominal - TEST on ARDUINOuno 5V
// float resist2 =  1000;        //                   1 kOhm nominal  - TEST on ARDUINOuno 5V
float  resist1 = 982000;         //   1 MOhm  680 kOhm nominal
float resist2 = 306000;         // 300 kOhm  220 kOhm nominal

void setup() {

#ifdef debug0
  Serial.begin(19200);
  Serial.println(F(""));
  Serial.print(F("Serial  START - press button!"));
  Serial.println(F(""));
#endif

  analogReference(INTERNAL);  // use INTERNAL (1.1V) for reference voltage

  display.begin(SSD1306_SWITCHCAPVCC,  0x3C);
  display.clearDisplay();
  display.setTextColor(WHITE);
  display.setFont(&FreeMono9pt7b);                        // PLAIN font

  display.setCursor(1, 10);
  display.print("Display  on.");
  display.setCursor(25, 30);
  display.print("press"); 
  display.setCursor(15,  50);
  display.print("to test");
  display.display();

  pinMode(pin_A,  INPUT_PULLUP);   //button
}

void loop() {
  do {
      button_A  = digitalRead(pin_A);
  } while ((button_A == 1) || ((millis()-button_delay_t)  < 500));

  button_delay_t = millis();

  #ifdef debug1
    Serial.print(F("Button  A ("));
    Serial.print(pin_A); 
    Serial.print(F(") = ")); 
    Serial.println(button_A);  
  #endif
  batteryCheck();
  showSCREEN();
}

void showSCREEN()  {
  display.clearDisplay();
  display.setTextColor(WHITE);
  display.setCursor(10+offset18_x,  20+offset18_y);
  display.setFont(&FreeMonoBold18pt7b);                        //  PLAIN font
  display.print(voltBatt,1);
  display.setCursor(85+offset18_x,  20+offset18_y);
  display.print("V");

  // display footer ***
  display.setCursor(47+offset9_x,  51+offset9_y);
  display.setFont(&FreeMono9pt7b);                        // PLAIN  font
  display.print(percBatt,1);
  display.print("%");

  if (percBatt  > 76 ) {                               // Battery level graphic display
    display.drawBitmap(0,  53, BatteryLevelFULL, 22, 12, WHITE);
  } else if (percBatt > 65 ) { 
      display.drawBitmap(0,  53, BatteryLevelMID, 22, 12, WHITE);
  } else { 
      display.drawBitmap(0,  53, BatteryLevelEMPTY, 22, 12, WHITE);
  }  
  display.display();          //Send  buffer to display
  delay(3000);

}

void batteryCheck() {
  referenceVoltage  = 1100;    // 1100 internal;
  V_source = 4.2;            // LiPo Vmax 4.2V -  UNO R3 5.056 - Vs from the divider calculation
  // using the REAL resistor values  makes it more "precise" - one can also set a fixed value
  V_out =  V_source*(resist2)/((resist1)+(resist2));              // UNO 0.889 - LiPo 1.05      - VOut from the divider calculation
  voltageError = 0;          // to empirically adjust ;-)

  analogamount  = analogRead(analoginput);
  percAREF=(analogamount/1024.00)*100;

  voltage=(analogamount/1024.00)*referenceVoltage+voltageError;       // in millivolts
  voltBatt=(voltage*((resist1)+(resist2))/(resist2))/1000;            // V_s = V_out * (R1+R2) / R2
  percBatt=(voltBatt/V_source)*100;

  #ifdef debug1
    Serial.print("V_out: ");
    Serial.println(V_out,3);  
    Serial.print("Lettura analog (0-1023): ");
    Serial.print(analogamount);
    Serial.print(" --------       % of AREF: ");
    Serial.print(percAREF,2);
    Serial.print(" --------       A0 (mV): ");   // compare with result of Voltage  Divider calculation Vout
    // for 5.056 (that I checked on Arduino1) and resistors  1K 4.7K is 0.889
    Serial.print(voltage,2);

    Serial.print(" --------       % of battery nominal: ");
    Serial.print(percBatt,2);
    Serial.print("  --------     Real - no divider (V): "); // if you check Arduino voltage should  be 5.0x
    Serial.println(voltBatt,2);
    Serial.println("");
  #endif
}

TEST Sketch on Arduino UNO

c_cpp

Breadboard and Arduino UNO test

1// Charger Wireless QI "snippet" by F.Stella 20220314
2
3#include
4  <SPI.h>
5#include <Wire.h>
6#include <Adafruit_GFX.h>
7#include <Adafruit_SSD1306.h>
8#include
9  <Fonts/FreeMono9pt7b.h>
10#include <Fonts/FreeMonoBold9pt7b.h>
11#include <Fonts/FreeMonoBold18pt7b.h>
12//
13  #include <Fonts/FreeMonoBold24pt7b.h>	
14
15#define SCREEN_WIDTH 128 // OLED
16  display width, in pixels
17#define SCREEN_HEIGHT 64 // OLED display height, in
18  pixels
19
20#define debug0      //attiva stampa DEBUG base e SERIAL
21#define
22  debug1      //attiva stampa DEBUG sezione1
23
24// Declaration for an SSD1306
25  display connected to I2C (SDA, SCL pins)
26#define OLED_RESET     4 // Reset pin
27  # (or -1 if sharing Arduino reset pin)
28Adafruit_SSD1306 display(SCREEN_WIDTH,
29  SCREEN_HEIGHT, &Wire, OLED_RESET);
30
31
32// 'BatteryLevels_bitmap_12x22', 22x12px
33const
34  unsigned char BatteryLevelFULL [] PROGMEM = {
35	0x1f, 0xff, 0xfc, 0x1f, 0xff,
36  0xfc, 0x18, 0x00, 0x0c, 0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0xfb, 
37	0xff, 0xec,
38  0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0x18, 0x00, 0x0c, 0x1f, 0xff,
39  
40	0xfc, 0x1f, 0xff, 0xfc
41};
42
43const unsigned char BatteryLevelMID []
44  PROGMEM = {
45	0x1f, 0xff, 0xfc, 0x1f, 0xff, 0xfc, 0x18, 0x00, 0x0c, 0xf8, 0x3f,
46  0xec, 0xf8, 0x3f, 0xec, 0xf8, 
47	0x3f, 0xec, 0xf8, 0x3f, 0xec, 0xf8, 0x3f, 0xec,
48  0xf8, 0x3f, 0xec, 0x18, 0x00, 0x0c, 0x1f, 0xff, 
49	0xfc, 0x1f, 0xff, 0xfc
50};
51
52const
53  unsigned char BatteryLevelEMPTY [] PROGMEM = {
54	0x1f, 0xff, 0xfc, 0x1f, 0xff,
55  0xfc, 0x18, 0x00, 0x0c, 0xf8, 0x00, 0xcc, 0xf8, 0x00, 0xcc, 0xf8, 
56	0x00, 0xcc,
57  0xf8, 0x00, 0xcc, 0xf8, 0x00, 0x0c, 0xf8, 0x00, 0xcc, 0x18, 0x00, 0x0c, 0x1f, 0xff,
58  
59	0xfc, 0x1f, 0xff, 0xfc
60};
61
62byte pin_A     = 2;
63byte button_A  =
64  0;
65
66int offset18_x = -2;
67int offset18_y = 22;
68int offset12_x = -2;
69int
70  offset12_y = 14;
71int offset9_x = -1;
72int offset9_y = 12;        
73
74unsigned
75  long button_delay_t = 0;
76
77int analoginput = 0;            // Battery CHECK
78  analog pin
79int analogamount = 0;           // stores incoming value
80float
81  percAREF = 0;
82float percBatt = 0;             // used to store our BATTERY percentage
83  charge value
84float voltBatt = 0;       
85float voltage = 0;              //
86  used to store voltage value
87float V_out = 0; 
88float V_source = 0; 
89float
90  referenceVoltage = 0;
91int voltageError = 0;
92// float resist1 = 4604;        //
93  4604 tester value 4.7 kOhm nominal - TEST on ARDUINOuno 5V
94// float resist2 =
95  1000;        //                   1 kOhm nominal  - TEST on ARDUINOuno 5V
96float
97  resist1 = 982000;         //   1 MOhm  680 kOhm nominal
98float resist2 = 306000;
99         // 300 kOhm  220 kOhm nominal
100
101void setup() {
102
103#ifdef debug0
104
105  Serial.begin(19200);
106  Serial.println(F(""));
107  Serial.print(F("Serial
108  START - press button!"));
109  Serial.println(F(""));
110#endif
111
112  analogReference(INTERNAL);
113  // use INTERNAL (1.1V) for reference voltage
114
115  display.begin(SSD1306_SWITCHCAPVCC,
116  0x3C);
117  display.clearDisplay();
118  display.setTextColor(WHITE);
119  display.setFont(&FreeMono9pt7b);
120                        // PLAIN font
121
122  display.setCursor(1, 10);
123  display.print("Display
124  on.");
125  display.setCursor(25, 30);
126  display.print("press"); 
127  display.setCursor(15,
128  50);
129  display.print("to test");
130  display.display();
131
132  pinMode(pin_A,
133  INPUT_PULLUP);   //button
134}
135
136void loop() {
137  do {
138      button_A
139  = digitalRead(pin_A);
140  } while ((button_A == 1) || ((millis()-button_delay_t)
141  < 500));
142
143  button_delay_t = millis();
144
145  #ifdef debug1
146    Serial.print(F("Button
147  A ("));
148    Serial.print(pin_A); 
149    Serial.print(F(") = ")); 
150    Serial.println(button_A);
151  
152  #endif
153  batteryCheck();
154  showSCREEN();
155}
156
157void showSCREEN()
158  {
159  display.clearDisplay();
160  display.setTextColor(WHITE);
161  display.setCursor(10+offset18_x,
162  20+offset18_y);
163  display.setFont(&FreeMonoBold18pt7b);                        //
164  PLAIN font
165  display.print(voltBatt,1);
166  display.setCursor(85+offset18_x,
167  20+offset18_y);
168  display.print("V");
169
170  // display footer ***
171  display.setCursor(47+offset9_x,
172  51+offset9_y);
173  display.setFont(&FreeMono9pt7b);                        // PLAIN
174  font
175  display.print(percBatt,1);
176  display.print("%");
177
178  if (percBatt
179  > 76 ) {                               // Battery level graphic display
180    display.drawBitmap(0,
181  53, BatteryLevelFULL, 22, 12, WHITE);
182  } else if (percBatt > 65 ) { 
183      display.drawBitmap(0,
184  53, BatteryLevelMID, 22, 12, WHITE);
185  } else { 
186      display.drawBitmap(0,
187  53, BatteryLevelEMPTY, 22, 12, WHITE);
188  }  
189  display.display();          //Send
190  buffer to display
191  delay(3000);
192
193}
194
195void batteryCheck() {
196  referenceVoltage
197  = 1100;    // 1100 internal;
198  V_source = 4.2;            // LiPo Vmax 4.2V -
199  UNO R3 5.056 - Vs from the divider calculation
200  // using the REAL resistor values
201  makes it more "precise" - one can also set a fixed value
202  V_out =  V_source*(resist2)/((resist1)+(resist2));
203              // UNO 0.889 - LiPo 1.05      - VOut from the divider calculation
204
205  voltageError = 0;          // to empirically adjust ;-)
206
207  analogamount
208  = analogRead(analoginput);
209  percAREF=(analogamount/1024.00)*100;
210
211  voltage=(analogamount/1024.00)*referenceVoltage+voltageError;
212       // in millivolts
213  voltBatt=(voltage*((resist1)+(resist2))/(resist2))/1000;
214            // V_s = V_out * (R1+R2) / R2
215  percBatt=(voltBatt/V_source)*100;
216
217
218  #ifdef debug1
219    Serial.print("V_out: ");
220    Serial.println(V_out,3);
221  
222    Serial.print("Lettura analog (0-1023): ");
223    Serial.print(analogamount);
224
225    Serial.print(" --------       % of AREF: ");
226    Serial.print(percAREF,2);
227
228    Serial.print(" --------       A0 (mV): ");   // compare with result of Voltage
229  Divider calculation Vout
230    // for 5.056 (that I checked on Arduino1) and resistors
231  1K 4.7K is 0.889
232    Serial.print(voltage,2);
233
234    Serial.print(" --------
235       % of battery nominal: ");
236    Serial.print(percBatt,2);
237    Serial.print("
238  --------     Real - no divider (V): "); // if you check Arduino voltage should
239  be 5.0x
240    Serial.println(voltBatt,2);
241    Serial.println("");
242  #endif
243}
244

// Charger Wireless QI "snippet" by F.Stella 20220314

#include
  <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include
  <Fonts/FreeMono9pt7b.h>
#include <Fonts/FreeMonoBold9pt7b.h>
#include <Fonts/FreeMonoBold18pt7b.h>
//
  #include <Fonts/FreeMonoBold24pt7b.h>	

#define SCREEN_WIDTH 128 // OLED
  display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in
  pixels

#define debug0      //attiva stampa DEBUG base e SERIAL
#define
  debug1      //attiva stampa DEBUG sezione1

// Declaration for an SSD1306
  display connected to I2C (SDA, SCL pins)
#define OLED_RESET     4 // Reset pin
  # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH,
  SCREEN_HEIGHT, &Wire, OLED_RESET);


// 'BatteryLevels_bitmap_12x22', 22x12px
const
  unsigned char BatteryLevelFULL [] PROGMEM = {
	0x1f, 0xff, 0xfc, 0x1f, 0xff,
  0xfc, 0x18, 0x00, 0x0c, 0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0xfb, 
	0xff, 0xec,
  0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0xfb, 0xff, 0xec, 0x18, 0x00, 0x0c, 0x1f, 0xff,
  
	0xfc, 0x1f, 0xff, 0xfc
};

const unsigned char BatteryLevelMID []
  PROGMEM = {
	0x1f, 0xff, 0xfc, 0x1f, 0xff, 0xfc, 0x18, 0x00, 0x0c, 0xf8, 0x3f,
  0xec, 0xf8, 0x3f, 0xec, 0xf8, 
	0x3f, 0xec, 0xf8, 0x3f, 0xec, 0xf8, 0x3f, 0xec,
  0xf8, 0x3f, 0xec, 0x18, 0x00, 0x0c, 0x1f, 0xff, 
	0xfc, 0x1f, 0xff, 0xfc
};

const
  unsigned char BatteryLevelEMPTY [] PROGMEM = {
	0x1f, 0xff, 0xfc, 0x1f, 0xff,
  0xfc, 0x18, 0x00, 0x0c, 0xf8, 0x00, 0xcc, 0xf8, 0x00, 0xcc, 0xf8, 
	0x00, 0xcc,
  0xf8, 0x00, 0xcc, 0xf8, 0x00, 0x0c, 0xf8, 0x00, 0xcc, 0x18, 0x00, 0x0c, 0x1f, 0xff,
  
	0xfc, 0x1f, 0xff, 0xfc
};

byte pin_A     = 2;
byte button_A  =
  0;

int offset18_x = -2;
int offset18_y = 22;
int offset12_x = -2;
int
  offset12_y = 14;
int offset9_x = -1;
int offset9_y = 12;        

unsigned
  long button_delay_t = 0;

int analoginput = 0;            // Battery CHECK
  analog pin
int analogamount = 0;           // stores incoming value
float
  percAREF = 0;
float percBatt = 0;             // used to store our BATTERY percentage
  charge value
float voltBatt = 0;       
float voltage = 0;              //
  used to store voltage value
float V_out = 0; 
float V_source = 0; 
float
  referenceVoltage = 0;
int voltageError = 0;
// float resist1 = 4604;        //
  4604 tester value 4.7 kOhm nominal - TEST on ARDUINOuno 5V
// float resist2 =
  1000;        //                   1 kOhm nominal  - TEST on ARDUINOuno 5V
float
  resist1 = 982000;         //   1 MOhm  680 kOhm nominal
float resist2 = 306000;
         // 300 kOhm  220 kOhm nominal

void setup() {

#ifdef debug0

  Serial.begin(19200);
  Serial.println(F(""));
  Serial.print(F("Serial
  START - press button!"));
  Serial.println(F(""));
#endif

  analogReference(INTERNAL);
  // use INTERNAL (1.1V) for reference voltage

  display.begin(SSD1306_SWITCHCAPVCC,
  0x3C);
  display.clearDisplay();
  display.setTextColor(WHITE);
  display.setFont(&FreeMono9pt7b);
                        // PLAIN font

  display.setCursor(1, 10);
  display.print("Display
  on.");
  display.setCursor(25, 30);
  display.print("press"); 
  display.setCursor(15,
  50);
  display.print("to test");
  display.display();

  pinMode(pin_A,
  INPUT_PULLUP);   //button
}

void loop() {
  do {
      button_A
  = digitalRead(pin_A);
  } while ((button_A == 1) || ((millis()-button_delay_t)
  < 500));

  button_delay_t = millis();

  #ifdef debug1
    Serial.print(F("Button
  A ("));
    Serial.print(pin_A); 
    Serial.print(F(") = ")); 
    Serial.println(button_A);
  
  #endif
  batteryCheck();
  showSCREEN();
}

void showSCREEN()
  {
  display.clearDisplay();
  display.setTextColor(WHITE);
  display.setCursor(10+offset18_x,
  20+offset18_y);
  display.setFont(&FreeMonoBold18pt7b);                        //
  PLAIN font
  display.print(voltBatt,1);
  display.setCursor(85+offset18_x,
  20+offset18_y);
  display.print("V");

  // display footer ***
  display.setCursor(47+offset9_x,
  51+offset9_y);
  display.setFont(&FreeMono9pt7b);                        // PLAIN
  font
  display.print(percBatt,1);
  display.print("%");

  if (percBatt
  > 76 ) {                               // Battery level graphic display
    display.drawBitmap(0,
  53, BatteryLevelFULL, 22, 12, WHITE);
  } else if (percBatt > 65 ) { 
      display.drawBitmap(0,
  53, BatteryLevelMID, 22, 12, WHITE);
  } else { 
      display.drawBitmap(0,
  53, BatteryLevelEMPTY, 22, 12, WHITE);
  }  
  display.display();          //Send
  buffer to display
  delay(3000);

}

void batteryCheck() {
  referenceVoltage
  = 1100;    // 1100 internal;
  V_source = 4.2;            // LiPo Vmax 4.2V -
  UNO R3 5.056 - Vs from the divider calculation
  // using the REAL resistor values
  makes it more "precise" - one can also set a fixed value
  V_out =  V_source*(resist2)/((resist1)+(resist2));
              // UNO 0.889 - LiPo 1.05      - VOut from the divider calculation

  voltageError = 0;          // to empirically adjust ;-)

  analogamount
  = analogRead(analoginput);
  percAREF=(analogamount/1024.00)*100;

  voltage=(analogamount/1024.00)*referenceVoltage+voltageError;
       // in millivolts
  voltBatt=(voltage*((resist1)+(resist2))/(resist2))/1000;
            // V_s = V_out * (R1+R2) / R2
  percBatt=(voltBatt/V_source)*100;


  #ifdef debug1
    Serial.print("V_out: ");
    Serial.println(V_out,3);
  
    Serial.print("Lettura analog (0-1023): ");
    Serial.print(analogamount);

    Serial.print(" --------       % of AREF: ");
    Serial.print(percAREF,2);

    Serial.print(" --------       A0 (mV): ");   // compare with result of Voltage
  Divider calculation Vout
    // for 5.056 (that I checked on Arduino1) and resistors
  1K 4.7K is 0.889
    Serial.print(voltage,2);

    Serial.print(" --------
       % of battery nominal: ");
    Serial.print(percBatt,2);
    Serial.print("
  --------     Real - no divider (V): "); // if you check Arduino voltage should
  be 5.0x
    Serial.println(voltBatt,2);
    Serial.println("");
  #endif
}

Downloadable files

TEST battery and display charge - breadboard sketch

This is a version of the "voltmeter" that uses an Arduino UNO and a simple bradboard set-up..

TEST battery and display charge - breadboard sketch

This is a version of the "voltmeter" that uses an Arduino UNO and a simple bradboard set-up..

TEST battery and display charge - breadboard sketch

Testing + Charging Li-Ion battery with a QI wireless receiver

This is the circuit as I use it in my projects

Testing + Charging Li-Ion battery with a QI wireless receiver

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