[Solicitation Order] Serial Ink Screen Perpetual Calendar Based on ESP32

Project Description

I have always wanted to make something for fun, and I happened to be inspired by the ink screen weather forecast made by duck, so I also planned to make a low-power personal display device. Considering low-power personal display devices, there is only Ink Screen, so we set the following goals:

1. This device needs to have low power consumption and preferably not need to be recharged for several years
2. Be more elegant and beautiful. After all, the technology can be bad, but the aesthetics cannot be bad.
3. Be practical and can really be used

Project function introduction

Calendar interface

Calendar function description

• Basic calendar functions (today’s date, week, month)
• lunar calendar
• Taboos in the Huangli calendar
• Twenty-four solar terms
• Holiday reminder
• Countdown to recent holidays
• National statutory holidays and time off
• Weather of the day, maximum and minimum temperature

development environment

vscode + esp-idf is used to write display-side programs keil + stm32 is used to write programs for power management chips python3 is used to write server-side calendar interfaces

Project properties

[x] Schematic design [x] PCB diagram design [x] PCB proofing [x] Welding test [x] Functional test [x] Program test

The calendar is currently in use and uses a small 400mAh battery. Since updates are not very frequent, it can basically be charged once every six months. If you use a large battery, you basically don’t need to charge it, which meets the design requirements.

Circuit explanation

1. Ink screen driver The ink screen driver copies the v2 version of the circuit in the epdiy project on github. This circuit is relatively simple and relatively low-cost, but the low power consumption is higher (this will be discussed later). Otherwise, there are no shortcomings. The most important things in the circuit are the five voltages, which are +22V/+15V/-20V/-15V and vCal. The voltages of +22V and -20V are mainly generated by LT1945, and +15V/-15V are generated by two LDOs, 7815 and 7915. VoltageCalibarate is generated by LM358 and adjustable resistor, because it needs to be adjusted according to the actual screen parameters. For details, please see the following document: epdiy document 2. esp32 circuit In esp32, because the ink screen has more IO, 74HC4094D is used for IO expansion, and As a result, the quiescent current of the device remains high, so another low-power microcontroller is used for power management . 3. The power management circuit uses STM32L010 as the power management chip. This was bought before the price of the chip increased. At that time it was 2 yuan/piece, but now it’s hard to tell. The power management is relatively simple. The STM32L010 is always charged. It wakes up every 4 hours from sleep state to supply power to the downstream stage. When the ink screen wakes up, it requests the latest calendar data from the server. According to actual measurements, the current during sleep can reach 1uA. Since it only wakes up once every 4 hours, the overall power consumption is very low.

software

The software aspect is relatively simple. Directly use the webimage routine in the epdiy routine. Pay attention to modifying the following definitions.

#define ESP_WIFI_SSID     "" //你的wifi信息
#define ESP_WIFI_PASSWORD  ""

#define STR_HELPER(x) #x
#define STR(x) STR_HELPER(x)
#define IMG_URL ("https://loremflickr.com/"STR(EPD_WIDTH)"/"STR(EPD_HEIGHT))//你的日历服务器的地址

After modification, just compile it. Note that the model of the ink screen should be EPD060SC4 and the PCB version should be V2/V3.

For details, please refer to: Quick Start - ESP32 epdiy

picture

Housing and PCB renderings

Precautions

• FPC terminals are difficult to weld. If possible, go to Taobao and open a small steel mesh for only 15 yuan, which can ensure the success rate of welding.

• As for the screen, I bought it from Xiaohuangyao, with a resolution of 600x600, a 3.8-inch screen with backlight and touch (no touch driver) and 16 levels of grayscale. It was only 20 yuan when I bought it, but now the price has increased.

• • -