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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2 respects

energy efficiency

smart appliances

data collection

Devices & Components

Arduino Uno Rev3

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)

Hardware & Tools

Solder Wire, Lead Free

Soldering iron (generic)

Solder Paste, Tack Flux

Software & Tools

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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