E-paper Display -- FAQ


2022-05-07 14:32

We have compiled all the collected e-ink display FAQs into a small tool that allows customers to easily find out the answers themselves. If you have a need, please click here to view.


Questionnaire Survey

PART 1 --- FAQ for E-ink Display





E-ink display cannot display images?

1.External Check: Please check whether the e-ink display FPC is inserted reversely, whether the FPC socket of the adapter board is artificially damaged, whether there is faulty soldering of the FPC socket and electronic components, and whether the electronic paper FPC is torn.If you use our development board, please check whether the P3 short-circuit cap on the motherboard is connected and whether the RESE dial switch on the adapter board is selected correctly.

2.Hardware Check: Measure the voltage of PREVGH and PREVGL to see if the boost is successful. If it is not successful, please check the relevant peripheral circuits, especially the MOS tube.

3.Software Check: If the boost is normal, check whether the software part, driver and pin definition are correct. Test the SCL and SDA signals of the driver board and confirm the correctness by comparing the SPI waveform in the specification.


Are there any requirements for E-ink use environment?

It needs to be shielded from direct sunlight, and moisture-proof and waterproof measures must be taken at the same time, otherwise the E-ink will be damaged to varying degrees under direct sunlight. Operate in strict accordance with the temperature and humidity range required by the specification. E-ink needs to be placed upside down when it is not used for a long time, and the screen is placed in an all white picture.


What should I do when using E-ink?

The refresh interval of SPI serial E-ink is at least 180s, especially for large-size E-ink. If the interval is too short, ghosting will appear, which will affect the refresh effect of the E-ink.


The Display screen offset?

Please check whether the power supply is insufficient or unstable. Insufficient or unstable power supply will cause data loss and image shift.Do not use an emulator for power supply.


The display screen is blurred?

It may be caused by a wrong mold-taking of images in bitmap conversion. If it is a partial blur, it may be caused by the user's wrong picture size or modulo resolution.


There are graying around the electronic paper display screen, etc

In the peripheral driving circuit, some capacitors have false soldering, which leads to the weakening of the driving ability of E-paper and may cause abnormal display.


E-ink displays images but with offset?

Insufficient power supply or unstable power supply will lead to data loss and image offset. It is not recommended to use the simulator for power supply.


Long-term power-on causes damage to the E-ink IC?

The E-ink should be powered off or enter deep sleep mode if it does not need to refresh for a long time.


Why there are stripes on the E-ink screen?

There should be no delay between e-paper initialization and iamge-display. A long delay will put the e-ink in voltage boosting for too long, which is easy to damage the e-ink.


Where is the origin coordinate of E-ink?

There are related annotations in the specification. The origin of most E-ink display is in the upper right corner, the vertical axis is the X axis, and the horizontal axis is the Y axis, except for some e-ink displays.


How to change the display direction of the screen?

All of our E-ink displays support 90-degree image rotation, which needs to be achieved by changing the modulus picture and modulus method. Some E-ink displays support 180-degree image rotation at the same time, which needs to be achieved through program initialization settings, specifications There are related setting instructions for the display direction in.


Why should it be reversed during refresh? How many times does the E-ink flicker in full refresh?

In fact, this is the process of E-ink display refreshing to eliminate afterimages. It is a normal phenomenon. Please pay attention to the final refreshed screen. E-ink display full refresh requires a splash screen to remove the afterimage of the previous picture, and there is no screen flickering phenomenon in a partial refresh. 


Why does SPI interface E-ink take longer than Parallel interface E-ink display to update images?

Because compared with 8-16 data lines of parallel interface E-ink, SPI series have only one data line.
Therefore, given the same time, the data-transmission ratio is 1:8/1:16, lower than parallel series.


Refresh response of E-ink display is slow in low temperature environment,even no image updated at all?

The E-ink display has a built-in temperature sensor. When the ambient temperature is low, the internally retrieved waveforms will be different, and the refresh time will also be different.If the image is not displayed in low temperature environment, it is necessary to prolong the delay to solve the problem.


Can the refresh time of E-ink be shortened?

Our current example program has already hit the limit refresh time of E-ink display IC. Shortening the refresh time can bring more serious ghosting. So, users are not recommended to shorten the time.


Does 2bit input in Specification refer to 2 level grayscale?

2bit input does not refer to 2 level grayscale. 2bit input refers to the number of positive voltage, negative voltage, 0 level and high resistance state. It is not a gray scale. The gray scale is reflected in the waveform.


How to calculate E-paper DPI?

Number of pixels in 1 inch, for example: 1.54 inch resolution 152*152, AA area 27.5x27.5, DPI=152/(27.5/25.39)=140


Any solution to achieve lower power consumption of E-paper display?

After E-paper enters deep sleep mode, turn off the driving circuit and IC power supply so that the electronic paper can achieve zero power consumption.


Current when E-paper in deep sleep mode is a little bit high?

The high current in deep sleep mode may be caused by the large capacitance of the boost part.


What are the differences between
GDEW0154T8 and GDEW0154T8D,GDEW0213T5 and GDEW0213T5D,GDEW026T0 and GDEW026T0D,GDEW029T5 and GDEW029T5D?

They look no different in external structure. The D series differs from no D series only in that IC because D is for UC8151D, an upgraded version of UC8151C. This new IC has better performance for E-paper to refresh quicker. 


The background color of three-color E-paper cannot be eliminated?

This problem is mainly caused by the existence of black images during long-term storage. When the three-color E-paper is not used for a long time, it needs to be placed completely white.Please follow the product use and storage precautions in the specification to operate the E-paper.


Why tri-color E-paper display red color looks black?

Usually there are several reasons: 1. Abnormal external boosting circuit and voltage is not enough 2.VCOM PIN FPC is torn 3.Film quality is bad, resulting this problematic red color display effect


Can three-color E-paper be used as monochrome E-paper?

Theoretically, it is possible. But when used in this way, you need to refresh the three-color E-paper with the corresponding monochrome program. If there is no corresponding monochrome program, you need to load external waveforms.


FAQs and using cautions for flexible E-paper display?

The IC of flexible E-paper is not allowed to be bent, and the display area is not allowed to be bent repeatedly. In addition, the so-called flexibility means that the substrate is relatively soft and the material becomes lighter and thinner. It is recommended that users do not place hard things under the E-paper when using it, so as to avoid damage to the substrate circuit, resulting in streaks and flickers on the screen during refresh.


What is the waveform of E-paper display and what is its function?

The grayscale of electrophoretic E-paper is determined by the spatial position of particles in microcapsules or cups. The electrophoretic phenomenon occurs between black particles and white particles under the action of voltage. The voltage sequence that promotes the electrophoretic movement of particles is the driving waveform of E-paper. The driving waveform is the core part of the E-paper display. The optimization of the driving waveform will directly affect the display effect of the display. The driving waveform file is used to explain the parameters formed by the voltage sequence that promotes the electrophoretic movement of particles, which needs to be called regularly when E-paper refreshes.

For different batches of E-paper diaphragms and electrophoretic matrix, due to materials, manufacturing process and other reasons, the voltage value required for driving the display will be different. What is reflected in the relationship between gray level, voltage and temperature is the waveform of electronic ink screen. Generally speaking, after the electrophoresis matrix of each batch is generated, there will be corresponding waveform files to WBF files exist in the form of. The manufacturer of the diaphragm provides the waveform files and electrophoresis matrix to the manufacturer of the E-paper screen, and then the manufacturer of the E-paper screen integrates the protection board, substrate and driver and provides them to the customer; If the waveform file does not correspond to the screen, it is likely that it cannot be displayed or the display effect is not ideal. The electronic ink screen / electronic paper display screen produced by Dalian Good Display Co., Ltd. has built the waveform file OTP into the driving IC of most E-paper screens (please confirm with the sales engineer when purchasing), so that users don't have to worry about it. Of course, customers can also drive E-paper by using external waveform files.


LUT and OTP stand for what?

LUT is the abbreviation of look up time and OTP is the abbreviation of one time program. LUT means to load waveform. Waveform are divided into OTP and register, of which OTP is the built-in waveform storage mode and register is the external waveform storage mode. However, there is a disadvantage in obtaining the display effect of local refresh by calling the external waveform file. That is, after the driver IC is upgraded and replaced, the waveform file will also be different. Customers need to modify the program when using the upgraded display screen, which brings a lot of inconvenience to customers to some extent. There is no problem when using OTP. Good Display will directly build the local refresh function into OTP in future product production to facilitate users' use.


How to configure the calling waveform for GDEW series E-paper?

GDEW can configure using data from command 0x00, specifics please refer to Specification.    0x1f is for OTP;0xbf is for Register.


Can E-paper display realize partial refresh?

Good Display has launched several types of graphic dot matrix E-paper, which can realize the partial refresh function. At present, there are 1.02, 2.13 and 2.9-inch flexible electronic ink screens, 1.54-inch, 2.13-inch, 2.6-inch, 2.7-inch, 2.9-inch and 4.2-inch electronic ink screens. Whether they can partial refresh mainly depends on the IC of E-paper.


How to understand partial refresh process of E-paper?

The partial refresh of GDEH E-paper is to refresh old data first, then new data, and finally update data. GDEH series needs to refresh background before start partial refresh.


How can ghosting of partial refresh be improved?

In order to improve this, we suggest that after partial refresh for 5 times, it is necessary to add a black-and-white full screen refresh display and increase the refresh interval.


What is the smallest unit of pixel points for partial refresh?

The minimum unit of the local refresh in the x-axis direction is 8 pixels. The smallest local refresh area that can be displayed by the E-paper is 8 pixels. If it is too small, the E-paper cannot be displayed normally.


How to partial refresh in different position at the same time?

It is necessary to perform a unified operation when designing the software. First, flash the data for different locations into the E-paper IC, and finally update data in unison.  


Why there is ghosting after fast refresh of E-paper?

Fast refresh is similar to partial refresh. And we recommend to follow as partial refresh, full refresh after five times of fast refresh.


How to drive the 6 inch E-paper display screen to get 16 level grayscale? Why can I only get the display effect of 4 levels with single chip microcomputer?

The sourcedata corresponding to 1 pixel of 6-inch E-paper display screen is 2 bits(bit1bit0=00:Pixel no drive,bit1bit0=01:Pixel drive to black,bit1bit0=00:Pixel drive to white,bit1bit0=11:Reserve),If the response time of our E-paper is 300ms and the frame rate is 50Hz, i.e. 20ms, the ideal situation is as follows:

(1) From black to white or white to black requires 300 / 20 = 15 frames of white drive or black drive

(2) The current pixel is black. We define it as grayscale 0. At this time, when driving 1 frame (20ms) to white, the pixel represents as grayscale 1

(3) The current pixel is black. At this time, drive 2 frames (40ms) to white, and the pixel represents as grayscale 2

(4) And so on, so that 16 grayscale can be controlled

Since one frame of single chip microcomputer scheme, such as STM32, is about 80ms, only four gray scales can be analyzed


Is it OK if I just use onepower supply for both the backlit and E-paper?

We don't recommend so because the backlit needs stronger current and it's better to add an extra power supply for it. Otherwise, it may affect the E-paper's display performance.


What's the effective distance using NFC on mobile to update the E-paper?

It's recommended to keep the mobile device 5mm or so above the NFC tag. Distance too far will lead to insufficient field strength and fail to drive the EPD.



PART 2 --- FAQ for Hardware of E-Paper Display

Circuit Design





How to select the components of the drive circuit?

The input voltage of electronic paper is generally 2.3-3.6V, and 3.3V is recommended.In order not to affect the display effect of electronic paper, the input voltage should be greater than 2.5V.It is recommended to add boost test points to facilitate circuit testing and product maintenance.


How to select the components of the drive circuit?

Inductance 10uH 1A winding inductance is recommended. Si1304BDL or Si1308EDL is recommended for MOS and AO3400 can also be used as a substitute.The schottky diode with the same parameters as MBR0530 should be selected, and the switching frequency should meet the actual requirements.In theory, the capacitor needs to withstand voltage of 50V, 25V can also be used in practical design.


How to choose the FPC connector and FPC length of SPI serial electronic paper?

SPI serial e-paper adopts 24PIN FPC connector with top contact or top and bottom electric touch, with needle distance of 0.5mm.It is recommended that the length of FPC cables not exceed 20cm; otherwise, data transmission errors may occur.


What is the GDR switching frequency of the E-paper IC?

GDR switching frequency is generally set by program, and the frequency is below 100khz. The built-in OTP version E-paper cannot modify this frequency by default.


Can 5V power supply drive e-paper directly?

We do not recommend direct use of 5V, when MCU power supply is 5V IO is 5V, because electronic paper works under 5V for a long time, easy to burn IC.


The e-paper sample program uses an analog SPI. Does e-paper support a hardware SPI?

E-paper sample program is used to simulate the SPI interface, users can change the IO port when porting the software.E-paper supports hardware SPI, but MISO pins need to be idle,the final connection is MOSI-sDIN or SCK-SCLK. You can define other I/O ports by yourself.


The MOS tube breakdown?

It might because the peripheral circuit has crosstalk and the MOS tube is abnormally turned on. Finally, the MOS tube broke down due to the long conduction time.


MCU RAM is relatively small, does the electronic paper display support external Flash?

At present, only 5.83 "(600*448) and 7.5" (640*384) e-paper display screens have external Flash components on the FPC. If users have requirements, please refer to the product specification, and the SPI part of the interface has a detailed description.We don't use Flash in our sample program for now. 


2.1: What status is the driver board when the E-paper is not connected?

When the E-paper is not connected to the driver board, the boost circuit, GDR, etc. are invalid.


2.3: Does the boost circuit automatically boost when E-paper only powers up?

The E-paper boost circuit is turned on with a fixed register. The boost circuit can be boosted only when the microcontroller sends the open boost command to the E-paper IC.


Can the BUSY pin of e-paper be omitted? What should I pay attention to?

The BUSY pin can be omitted, but a software delay is required to simulate the actual state of the BUSY pin,The delay should be longer than the refresh time to ensure that the e-paper is refreshed within an effective time. If the delay is too short, the actual refresh display will be affected.


The BUSY pin is always busy?

The e-paper BUSY pin is always BUSY. Confirm that the BUSY pin is set to the pull-up input mode during initialization, and then check the IO interface level. For example, the IO of the normal e-paper driver is 3.3V, while the Arduino is 5V by default, which may cause this phenomenon.If the UC series e-paper is used, you can cancel the 0x71 command in the BUSY detection function. This operation does not affect the function determination of the BUSY pin.


What is the role of TSCL and TSDA in the specification?

These two PINS are connected to external temperature sensors. Since the early electronic paper IC has no built-in temperature sensor, it needs to obtain the ambient temperature externally,Nowadays, almost all serial electronic paper on the market have IC built-in temperature sensor.


How to achieve 3-wire SPI?

The only difference between 3-wire and 4-wire is the D / C pin. If 3-wire SPI is used, the D / C pin needs to be connected to GND, and then the D / C function is realized through the software. The D / C function can be added every time during data transmission


What TCON solution for E Ink parallel port E-paper display do we have?

At present, E Ink parallel port E-paper TCON driver mainly uses it8951 produced by ITE company, and some ereader clients use RK company's chip, which has built-in TCON function.




Development Board





Does serial port electronic paper development board support serial port communication and serial port download?

Our company's STM32, ESP32, ESP8266 and Arduino development platform all have USB-to-serial chip, which can be directly connected to PC and development board through USB cable for serial operation and download.


STM32 development board how to use serial port download program

The STM32 development board can be short-circuited to the corresponding Boot interface(P12) through the short-circuited cap can be downloaded through the serial port. The software used for downloading is FLYMCU, and the downloading method is similar to C51 (after downloading, disconnect the short-circuited port from P12).


Does the serial e-paper development board support current measurement?

Our STM32, ESP32, ESP8266 and Arduino development platforms all support measurement of onboard power consumption and electronic paper power consumption.


Can serial e-paper development boards connect to other peripherals or drive multiple transfer boards?

Our STM32, ESP32, ESP8266 and Arduino development platforms extend all pins of MCU. Users can connect other peripherals through the development board to design and develop other products.The development board can drive multiple transfer boards, and the interface has been reserved.


Does Arduino, ESP32,ESP8266 development board support driver touch screen?

Arduino, ESP32,ESP8266 development board can directly drive the touch screen, need to define their own IO ports, generally including SDA, SCL, RST, INT.


Can DESPI-C03's touch interface share IO ports with e-paper?

Some touch screen IC and electronic paper IC will conflict in the default level, leading to the inability to share a set of IO ports, so you can test the relevant functions separately when testing.


What functions does DESPI-K154 have?

It supports touch panel, front light, Flash expansion, SD card expansion, custom flowing water light and so on.



PART 3 --- FAQ for Software of E-Paper Display

Bitmap Conversion





What tools do I use to generate an array of images?

If you use Windows system, the mold taking software can use Image2Lcd (registration code "0000-0000-0000-0000-6A3b). For specific use process, please check the corresponding mold taking instructions of each screen.

You can also use our ImageToEpd software, which can be operated by one key, simple and convenient to use,This software can operate three-color map with one key, and the other two software need to use image processing software (PhotoShop, etc.) to separate two parts, one part is black and white map, the other part is red and white map, and operate the two pictures respectively.

* You also can refer to the following link for the procedures and instructions of automatic e-paper display bitmap conversion: https://github.com/abao66669999/Good-Display-Software


Can E-paper still do partial refresh under low temperature condition?

Generally, the partial refresh function has the best effect at room temperature (above 20 degrees).
If it is lower than 20 degrees, it needs to prolong the partial refresh time to offset the residual shadow at low temperature. In addition, partial refresh is not supported below 0 degrees.


How can I do the Bitmap conversion for tri-color EPD?

If You may directly use the helpful tool-ImageToEPD by Good Display to realize it.




E-paper Display Driver Program





What should I do if I have problems using Keil software?

Problem 1: Can't compile the sample program we provided?

Please make sure the Keil application has correctly installed.Please install the J-link driver first. If it still can’t recognize, please use the computer system driver application to complete the missing drivers.

Problem 2: Can the project of Keil4 be downloaded with keil5?

Yes, but you need to recompile the Keil4 project with Keil5 and then download it.

Problem 3: Prompt 'Flash download failed' when download program with Keil5?

This is mainly because you did not add Flash option in Keil5.

Problem 4:Display the original image even after writing new image data?

Please confirm whether Keil has been recompiled after updating the image data, whether there is no error in the compilation, and whether the program has been downloaded successfully.      


How to write E-paper driver programs?

There will be a drive flowchart in the E-paper specification. Please refer to the flowchart to write the code. There are detailed control command descriptions in the specification.


There is delay between two images, can it be removed?

This delay can be removed. The necessary delay of refreshing is achieved by the BUSY function. The delay in the sample program is mainly for giving users more time to observe the display process of the E-paper.


How to change the E-paper display refresh speed?

SPI serial E-paper can change the refresh speed by adjusting the PLL refresh frequency.


Abnormal lines appear on the screen after changing the refresh frequency?

A high refresh rate can damage the diaphragm of electronic paper, causing abnormal lines to appear on the screen.


Why doesn't an e-paper display an image after it goes into deep sleep mode and refreshes again?

When the e-paper enters the deep sleep mode and needs to be refreshed again, the software needs to initialize the e-paper again.


E-paper can't display image after switching from partial display to full display?

After the e-paper is switched from partial display to full display, the full display initialization function needs to be added


Where is e-paper display data stored?

E-paper IC internal corresponding RAM memory, monochrome and tri-color have corresponding registers.UC:0x10 and 0x13,SSD:0x24 and 0x26.


Can parallel port E-paper support Linux system migration?

This is OK, but there is no tutorial for parallel port Linux migration. Please migrate according to the migration process of other MCU platforms.


Does the DEMO board support GCC build environment?

The development environment is currently not supported. The DESPI board is the Keil environment and the Arduino board ESP32 board and ESP8266 board is the Arduino environment.


UC-series E-paper during initialization
get stuck at BUSY judgment

This usually occurs in some single-chip computers. The user can comment out the 0x71 command in the busy function. If still no improvement, the corresponding delay function can be used to replace the BUSY judgment.


Can tri-color E-paper do VCOM adjustment?

The early tri-color E-paper waveform files were external, and the VCOM can be adjusted through initialization. Now the E-paper waveform files are built-in, and the VCOM cannot be changed through initialization.


Differences between UC series and SSD series

UC series is the chip of Ultrachip and SSD series is the chip of Solomon. The driving process of these two types in driving E-paper is similar, the driving code is completely different, and the BUSY signal feedback also the opposite.


Do the states of BUSY pin affect the current in sleep mode?

T For BUSY pin in floating input, pull-up input, they will not affect the current; for pull-down input, it will generate a current about 80uA in sleep mode.


The difference between quick update and partial update?

U Quick update is a kind of full refresh where there will be flickering in the screen while in partial update, there is no flickering.


VCOM voltage setting parallel port E-paper

Normally, there will be negative voltage value printed on the FPC of the E-paper and you can do the setting according that in the software, which usually is to be -2.0V.


What is the most direct factor for the refresh rate of E-paper?

Environmental temperature. Usually, E-paper Display will refresh at different rate according to different temperature, higher temperature, fast refresh rate.


What is the biggest factor for the speed of receiving data of E-paper?

The writing speed of SPI is generally determined by the IO inversion speed of MCU, that is, the processing speed of MCU, and the hardware SPI is determined by the main frequency of SPI.


Which MCU supports driving electronic paper display?

STM32, STM8, 51 and PIC are all supported. In addition, the development board with Linux system is also supported, such as Raspberry Pi. The driving condition is to have enough IO for E-paper connection.


What is the most power-saving method for E-paper display?

After a complete picture is refreshed, cut off the power supply of the electronic paper drive board and screen to achieve standy 0 power consumption of E-paper display.




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