Arduino Nano 0.91 OLED Battery Indicator

I couldn't find an open source 0.91 OLED Battery indicator code and this is kind of important to avoid spicy pillows. Stay safe with this by adding this simple project to your battery powered devices!

Aug 27, 2024

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Energy Efficiency

Monitoring

Tracking

Components and supplies

B25 0 to 25V Voltage Sensor Module

Geekcreit 0.91 Inch 128x32 IIC I2C Blue OLED LCD Display DIY Module SSD1306 Driver IC DC 3.3V 5V

Arduino Nano

Apps and platforms

Arduino IDE

Project description

Code

BatteryIndicator091Nano.ino

Author SerMumble

1#include <U8g2lib.h>
2#include <U8x8lib.h>
3#include <Wire.h>
4
5//Check the U8G2 library and read about what display you need. These are just some generic 128x32 OLED displays.
6//If you notice part of your display looks cut off or someone sprinkled salt on it, uncomment and comment these displays to switch them.
7//U8G2_SSD1305_128X32_NONAME_F_HW_I2C display(U8G2_R2);
8//U8G2_SSD1305_128X32_ADAFRUIT_F_HW_I2C display(U8G2_R2);
9//U8G2_SSD1306_128X32_WINSTAR_F_HW_I2C display(U8G2_R2);
10U8G2_SSD1306_128X32_UNIVISION_F_HW_I2C display(U8G2_R2);
11
12//Default starting values. Please do not change.
13int value = 0;
14float voltage;
15uint8_t percent = 100;
16
17//Change resistance to calibrate voltage sensor. Use a multimeter to check the exact resistance of your two resisistors.
18//If the measured voltage is too low, increase the resistance difference between R1 and R2.
19//If the measured voltage is too high, decrease the resistance difference between R1 and R2.
20float R1 = 30500.0; //29700.0; //30000.0; //47000.0;
21float R2 = 7340.0; //7500.0; //33000.0;
22
23//This is for the battery percentage displayed and printed.
24//Lithium single cell batteries typically range between 0% at 3.2V and 100% at 4.2V
25//Litium 4S batteries are a multiple of 4 times the single cell. 0% at 12.8V and 100% at 16.8V
26int BatMinVolt = 3.2;
27int BatMaxVolt = 4.2;
28
29//sample size for smoothing. Decrease for a more responsive and twitchy measurement. Increase if you want the updates to take longer.
30int numReadings = 50; //10;
31
32// This is the battery fill mode
33// BATTERY_MODE_SOLID = 1 means the battery bitmap will be filled with
34// a solid rectangle according to the battery charge.
35// BATTERY_MODE_SOLID = 0 means the battery will be filled with a
36// rectangle subdivided in 3. If the battery level is 66% or more, it will
37// draw 3 rectangles. If it's 33% or more, it will draw 2 rectangles. It will
38// draw 1 rectagle if the battery is less than 33%.
39
40#define BATTERY_MODE_SOLID 1
41
42// This is the battery outline bitmap. The commented bitmap is for 128x64 and the active bitmap is for 128x32.
43//Original code was modified from this guide which supplied the bitmap and initial script
44//https://www.artekit.eu/doc/guides/propboard-battery-indicator/
45/*static unsigned char battery_bitmap[] = {
46   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
47   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
48   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
49   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
50   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
51   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
52   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
53   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
54   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
55   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
56   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
57   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
58   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
59   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
60   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
61   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
62   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
63   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
64   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
65   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
66   0x00, 0x00, 0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
67   0xff, 0x03, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
68   0xff, 0xff, 0xff, 0xff, 0xff, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
69   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
70   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
71   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
72   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
73   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
74   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
75   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
76   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
77   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
78   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
79   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
80   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
81   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
82   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
83   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
84   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
85   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
86   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
87   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
88   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
89   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
90   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
91   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
92   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
93   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
94   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
95   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
96   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
97   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
98   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
99   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
100   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
101   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
102   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
103   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
104   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
105   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
106   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
107   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
108   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff,
109   0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x07, 0x00, 0x00,
110   0x00, 0x00, 0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
111   0xff, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
112   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
113   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
114   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
115   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
116   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
117   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
118   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
119   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
120   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
121   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
122   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
123   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
124   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
125   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
126   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
127   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
128   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
129   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
130   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
131   0x00, 0x00, 0x00, 0x00 };*/
132
133static unsigned char battery_bitmap[] = {
134   0x00, 0x00, 0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
135   0xff, 0x03, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
136   0xff, 0xff, 0xff, 0xff, 0xff, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
137   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
138   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
139   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
140   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
141   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
142   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
143   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
144   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
145   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
146   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
147   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
148   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
149   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
150   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
151   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
152   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
153   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
154   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
155   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
156   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
157   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
158   //0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
159   //0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
160   //0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
161   //0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
162   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
163   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
164   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
165   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
166   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
167   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
168   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
169   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
170   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
171   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
172   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
173   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
174   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
175   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
176   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff,
177   0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x07, 0x00, 0x00,
178   0x00, 0x00, 0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
179   0xff, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
180   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
181   0x00, 0x00, 0x00, 0x00 };
182
183// This is the area inside the battery bitmap, in pixels
184#define CHARGE_AREA_START_X     20
185#define CHARGE_AREA_START_Y     3 //Change to 18 if using a 128x64 display
186#define CHARGE_AREA_WIDTH       83
187#define CHARGE_AREA_HEIGHT      25
188
189// This is the main function, and the one you will want to transplant to your
190// code. Pass the battery charge percent and it will draw the battery with
191// the corresponding charge level.
192void showBatteryLevel(uint8_t percent)
193{
194    uint8_t width;
195
196    if (percent > 100)
197        percent = 100;
198
199    display.clearBuffer();
200    //display.drawXBM(0, 0, 128, 64, battery_bitmap); //for 128x64 display
201    display.drawXBM(0, 0, 128, 32, battery_bitmap); //for 128x32 display
202
203    if (BATTERY_MODE_SOLID)
204    {
205        width = (percent * CHARGE_AREA_WIDTH) / 100;
206        display.drawBox(CHARGE_AREA_START_X, CHARGE_AREA_START_Y, width, CHARGE_AREA_HEIGHT);
207    } else {
208        uint8_t bars;
209        if (percent >= 66)
210        {
211            // Show three bars
212            bars = 3;
213        } else if (percent >= 33)
214        {
215            // Show two bars
216            bars = 2;
217        } else if (percent > 0)
218        {
219            // Show one bar
220            bars = 1;
221        } else {
222            // Show nothing
223            bars = 0;
224        }
225
226        uint8_t offset = CHARGE_AREA_START_X;
227        for (uint8_t i = 0; i < bars; i++)
228        {
229            //display.drawBox(offset, CHARGE_AREA_START_Y, 27, CHARGE_AREA_HEIGHT);
230            display.drawBox(offset, CHARGE_AREA_START_Y, 27, CHARGE_AREA_HEIGHT);
231            offset += 28;
232        }
233    }
234
235    //Print Voltage, percentage, and black contrast box behind the numbers so they are visible.
236    display.setColorIndex(0); //White color
237    display.drawBox(28, 10, 65, 12);
238    display.setColorIndex(1); //Black color
239    display.setFont(u8g2_font_ncenB08_tr);
240    display.setCursor(30,20);
241    display.print(voltage);
242    display.drawStr(52,20,"V");
243    display.setCursor(70,20);
244    display.print(percent);
245    display.drawStr(83,20,"%");
246    display.sendBuffer();
247}
248
249void setup()
250{
251    // Initialize the display object
252    display.begin();
253    Serial.begin(9600);
254}
255
256
257void loop()
258{
259    // Some test code to scan all the battery levels
260    showBatteryLevel(percent);
261    float temp;
262    
263    //comment here to remove smoothing
264    for (int i = 0; i < numReadings; i++){
265      voltage = voltage + (analogRead(A0)*(5.0/1024)*((R1 + R2)/R2));
266      delay(100);
267      }
268    voltage = voltage /(numReadings+1);
269    //end comment here to remove smoothing
270    
271    //uncomment to remove smoothing
272    //voltage = analogRead(A0)*(5.0/1024)*((R1 + R2)/R2);
273    
274    //Calculate battery percentage based on measured voltage and expected battery minimum and max voltage. 
275    //If no battery is detected or extreme overvolt is measured, set battery percentage to 0% to alert user something is wrong.
276    percent = ((voltage-BatMinVolt)/(BatMaxVolt-BatMinVolt))*100;
277    if (percent>110)
278        percent = 0;
279    
280    //Uncomment for serial monitor debug if you have no display
281    /*
282    Serial.print("Voltage =");
283    Serial.println(voltage);
284    Serial.print("Percent =");
285    Serial.println(percent);
286    */
287
288    delay(1000);
289}

#include <U8g2lib.h>
#include <U8x8lib.h>
#include <Wire.h>

//Check the U8G2 library and read about what display you need. These are just some generic 128x32 OLED displays.
//If you notice part of your display looks cut off or someone sprinkled salt on it, uncomment and comment these displays to switch them.
//U8G2_SSD1305_128X32_NONAME_F_HW_I2C display(U8G2_R2);
//U8G2_SSD1305_128X32_ADAFRUIT_F_HW_I2C display(U8G2_R2);
//U8G2_SSD1306_128X32_WINSTAR_F_HW_I2C display(U8G2_R2);
U8G2_SSD1306_128X32_UNIVISION_F_HW_I2C display(U8G2_R2);

//Default starting values. Please do not change.
int value = 0;
float voltage;
uint8_t percent = 100;

//Change resistance to calibrate voltage sensor. Use a multimeter to check the exact resistance of your two resisistors.
//If the measured voltage is too low, increase the resistance difference between R1 and R2.
//If the measured voltage is too high, decrease the resistance difference between R1 and R2.
float R1 = 30500.0; //29700.0; //30000.0; //47000.0;
float R2 = 7340.0; //7500.0; //33000.0;

//This is for the battery percentage displayed and printed.
//Lithium single cell batteries typically range between 0% at 3.2V and 100% at 4.2V
//Litium 4S batteries are a multiple of 4 times the single cell. 0% at 12.8V and 100% at 16.8V
int BatMinVolt = 3.2;
int BatMaxVolt = 4.2;

//sample size for smoothing. Decrease for a more responsive and twitchy measurement. Increase if you want the updates to take longer.
int numReadings = 50; //10;

// This is the battery fill mode
// BATTERY_MODE_SOLID = 1 means the battery bitmap will be filled with
// a solid rectangle according to the battery charge.
// BATTERY_MODE_SOLID = 0 means the battery will be filled with a
// rectangle subdivided in 3. If the battery level is 66% or more, it will
// draw 3 rectangles. If it's 33% or more, it will draw 2 rectangles. It will
// draw 1 rectagle if the battery is less than 33%.

#define BATTERY_MODE_SOLID 1

// This is the battery outline bitmap. The commented bitmap is for 128x64 and the active bitmap is for 128x32.
//Original code was modified from this guide which supplied the bitmap and initial script
//https://www.artekit.eu/doc/guides/propboard-battery-indicator/
/*static unsigned char battery_bitmap[] = {
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
   0xff, 0x03, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
   0xff, 0xff, 0xff, 0xff, 0xff, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff,
   0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x07, 0x00, 0x00,
   0x00, 0x00, 0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
   0xff, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00 };*/

static unsigned char battery_bitmap[] = {
   0x00, 0x00, 0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
   0xff, 0x03, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
   0xff, 0xff, 0xff, 0xff, 0xff, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   //0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   //0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   //0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   //0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x7f, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00,
   0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff,
   0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x07, 0x00, 0x00,
   0x00, 0x00, 0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
   0xff, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
   0x00, 0x00, 0x00, 0x00 };

// This is the area inside the battery bitmap, in pixels
#define CHARGE_AREA_START_X     20
#define CHARGE_AREA_START_Y     3 //Change to 18 if using a 128x64 display
#define CHARGE_AREA_WIDTH       83
#define CHARGE_AREA_HEIGHT      25

// This is the main function, and the one you will want to transplant to your
// code. Pass the battery charge percent and it will draw the battery with
// the corresponding charge level.
void showBatteryLevel(uint8_t percent)
{
    uint8_t width;

    if (percent > 100)
        percent = 100;

    display.clearBuffer();
    //display.drawXBM(0, 0, 128, 64, battery_bitmap); //for 128x64 display
    display.drawXBM(0, 0, 128, 32, battery_bitmap); //for 128x32 display

    if (BATTERY_MODE_SOLID)
    {
        width = (percent * CHARGE_AREA_WIDTH) / 100;
        display.drawBox(CHARGE_AREA_START_X, CHARGE_AREA_START_Y, width, CHARGE_AREA_HEIGHT);
    } else {
        uint8_t bars;
        if (percent >= 66)
        {
            // Show three bars
            bars = 3;
        } else if (percent >= 33)
        {
            // Show two bars
            bars = 2;
        } else if (percent > 0)
        {
            // Show one bar
            bars = 1;
        } else {
            // Show nothing
            bars = 0;
        }

        uint8_t offset = CHARGE_AREA_START_X;
        for (uint8_t i = 0; i < bars; i++)
        {
            //display.drawBox(offset, CHARGE_AREA_START_Y, 27, CHARGE_AREA_HEIGHT);
            display.drawBox(offset, CHARGE_AREA_START_Y, 27, CHARGE_AREA_HEIGHT);
            offset += 28;
        }
    }

    //Print Voltage, percentage, and black contrast box behind the numbers so they are visible.
    display.setColorIndex(0); //White color
    display.drawBox(28, 10, 65, 12);
    display.setColorIndex(1); //Black color
    display.setFont(u8g2_font_ncenB08_tr);
    display.setCursor(30,20);
    display.print(voltage);
    display.drawStr(52,20,"V");
    display.setCursor(70,20);
    display.print(percent);
    display.drawStr(83,20,"%");
    display.sendBuffer();
}

void setup()
{
    // Initialize the display object
    display.begin();
    Serial.begin(9600);
}


void loop()
{
    // Some test code to scan all the battery levels
    showBatteryLevel(percent);
    float temp;
    
    //comment here to remove smoothing
    for (int i = 0; i < numReadings; i++){
      voltage = voltage + (analogRead(A0)*(5.0/1024)*((R1 + R2)/R2));
      delay(100);
      }
    voltage = voltage /(numReadings+1);
    //end comment here to remove smoothing
    
    //uncomment to remove smoothing
    //voltage = analogRead(A0)*(5.0/1024)*((R1 + R2)/R2);
    
    //Calculate battery percentage based on measured voltage and expected battery minimum and max voltage. 
    //If no battery is detected or extreme overvolt is measured, set battery percentage to 0% to alert user something is wrong.
    percent = ((voltage-BatMinVolt)/(BatMaxVolt-BatMinVolt))*100;
    if (percent>110)
        percent = 0;
    
    //Uncomment for serial monitor debug if you have no display
    /*
    Serial.print("Voltage =");
    Serial.println(voltage);
    Serial.print("Percent =");
    Serial.println(percent);
    */

    delay(1000);
}

Downloadable files

Battery Indicator Code For 0.91 OLED

Instructions are commented in the code!

BatteryIndicator091Nano.ino

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