ePaper displays are more and more popular mainly thanks to low power consumption and wide viewing angle. But what board you should use to control it? We designed ESPink, small board focused on the lowest power consumption, easy connection of sensors and big memory for graphics. The ESPink is based on ESP32 what is one of the most popular Wi-Fi and Bluetooth modules.
What is on board? Connector for connection of ePaper/eInk. The ePaper is very low power, but it is drawing current during sleep (a few uA). To achieve the lowest current, we assembled transistor between power and input of ePaper. Thanks to this, the current through ePaper during the sleep is zero. The gate of transistor is connected to GPIO2 and the power supply for ePaper is enabled in case GPIO2 is set to HIGH. The same GPIO (GPIO2) is also used for enabling of power supply for I2C sensor connected to uŠup connector.
One more feature is the built-in programmer, where we used really low power programmer.
The board is powered from lipol battery which is chargered from USB-C, no longer micro USB. The design is ready for measurement of battery voltage. The voltage divider is connected to battery and GPIO34 where is ADC input.
The connection of sensors is so easy and safe thanks to our I2C μŠup connector. The connector includes lock and the pinout is the same for all sensors and board made by laskakit.cz.
The sensors which include μŠup connector are LaskaKit SHT40 Sensor of temperature and humidity and LaskaKit SCD41 Sensor CO2, temperature and humidity .
We also added SPI μŠup connector for extending with for example for microSD reader.
ESP32 includes a lot of GPIO what we didn't use, but we keep them for custom purpose. So you can solder what you want.
The ESPink was precisly designed for low power, but also the labeled GPIO what we used on board. On the bottom side is solder bridge, which defines the charging current. By default it is set 400 mA, but you can choose 260 mA. Just cut the this track and put a drop of solder on the oposite side of solder bridge.
ESPink is available on https://www.laskakit.cz/laskakit-espink-esp32-e-paper-pcb-antenna/ We prepared example codes available on this link https://github.com/LaskaKit/ESPink/tree/main/SW