Q: The following situation occurs when running the Python program on the Raspberry Pi?
Enter the command: ls /dev/spi*
The result may look like the image:
This is because the SPI interface is occupied in the /boot/config.txt file:
The solution is as follows:
Remove the occupation of spi0-0 in the /boot/config.txt file.
Modify the position shown in the image in the /e-Paper/RaspberryPi_JetsonNano/lib/waveshare_epd/epdconfig.py file to 0,1.
Q: How to use other custom fonts?
Currently, we do not provide other font files. You can refer to the custom font compiler shared by users to generate font files for testing. Note: This tool is not officially maintained by Waveshare and is for learning purposes only.
Q: When driving the e-Paper with STM32, MDK compilation shows insufficient space?
Our example uses the STM32f103ZET6. If the customer changes to another model in MDK, such as STM32F103RBT6, the RAM space becomes smaller. You need to modify the stack size and heap size in the startup file based on the original.
Q: Questions about the datasheet. When to use Data Start Transmission 1 and when to use Data Start Transmission 2? In KW mode, what is OLD data and what is NEW data?
In Data Start Transmission 1, the previous data, i.e., the so-called "OLD" data, is sent. In the program, 0x00 is usually sent directly. In Data Start Transmission 2, the data to be refreshed, i.e., the so-called "NEW" data, is sent.
Q: Chinese characters cannot be displayed on the e-Paper?
Our example's Chinese font library uses the GB2312 encoding. Please change your xxx_test.c file to the GB2312 encoding format, compile and download it, and it will display normally.
Q: Black border appears on the e-Paper display?
You can set the border display color through the Border Waveform Control register or the VCOM AND DATA INTERVAL SETTING register.
Q: After several partial refreshes in multiple locations, the text becomes light?
In this case, the customer needs to reduce the number of partial refresh locations and perform a full clear after 5 partial refreshes.
Q: When the e-Paper is in deep sleep mode, the first refresh after waking up has an unclean image. How to solve this?
The process of re-waking the e-Paper is essentially a power-on process. Therefore, when the EPD wakes up, it must first perform a clear screen action to minimize ghosting as much as possible.
Q: When testing the program, the program gets stuck at e-Paper busy?
It may be caused by unsuccessful SPI driver:
First, check if the wiring is correct.
Check if SPI is enabled and if the parameters are configured correctly. (Parameters such as baud rate, mode, etc.)
Q: Why is it impossible to display an image after a partial refresh followed by a full refresh?
When switching the e-Paper from partial refresh to full refresh, the full refresh initialization function needs to be added.
Q: Why does the Python program print information normally but the e-Paper does not respond?
It may be that a C language example based on the BCM2835 library was previously run. In this case, you need to restart the Raspberry Pi and then run the Python example.
Q: When running the Python program, an error is reported: ImportError: No module named Image?
Install the imaging library using the command sudo apt-get install python-imaging.
Yes. The board now has an onboard level shifter chip, supporting 5V drive.
Q: What should be considered when designing a driver board?
The rated input voltage for the e-Paper is 2.3~3.6V. If it's a 5V system, level shifting is needed. Additionally, the voltage should preferably not be lower than 2.5V to avoid affecting the e-Paper display effect.
For component selection, you can use the models in the schematic we provide or choose according to the datasheet.
Q: Can I use a software SPI?
Yes, but ensure the timing is correct.
Q: Why is the BUSY pin always busy?
Verify if SPI communication is normal.
Verify if the BUSY pin is correctly initialized as an input mode.
It may be that the reset was not performed properly. Try shortening the duration of the low level during reset. (Because the driver circuit includes a power-off switch, a reset low level that is too long may cause the driver board to power off, leading to reset failure.)
If the busy check function sends the 0x71 command, try commenting it out.
Q: What are the specifications of the screen cable interface?
Q: What is the operating environment for the e-Paper?
Working Conditions: Temperature range: 0~50°C; Humidity range: 35%~65%RH.
Storage Conditions: Temperature range: below 30°C; Humidity range: below 55%RH; Maximum storage time: 6 months.
Transportation Conditions: Temperature range: -25~70°C; Maximum transport time: 10 days.
After Unpacking: Temperature range: 20°C±5°C; Humidity range: 50±5%RH; Maximum storage time: Assembly to be completed within 72 hours.
Q: Precautions for e-Paper refreshing
Refresh Modes:
Full Refresh: The e-Paper will flash multiple times during the refresh process (the number of flashes depends on the refresh duration). Flashing is to clear ghosting and achieve the best display effect.
Partial Refresh: The e-Paper has no flashing effect during the refresh process. Users employing the partial refresh function should note that after several refreshes, a full refresh operation is required to clear ghosting; otherwise, the ghosting problem will worsen and may even damage the screen. (Currently, only some black and white e-Paper screens support partial refresh. Please refer to the product page for details.)
Refresh Frequency:
During use, it is recommended to set the refresh interval for the e-Paper to at least 180 seconds. (Except for products that support partial refresh function)
During standby (i.e., after a refresh operation), it is recommended to set the e-Paper to sleep mode or power it off (the power supply part of the e-Paper can be disconnected using an analog switch) to reduce power consumption and extend the e-Paper's lifespan. (If some e-Paper screens are powered on for a long time, irreversible screen damage may occur.)
Usage Location:
It is recommended to use the e-Paper indoors; outdoor use is not recommended.
If the usage scenario is outdoors, we do not guarantee its display effect. If the e-Paper is damaged due to outdoor use, we do not provide warranty service.
The following are some protective measures for outdoor use. We do not guarantee that the e-Paper will function normally even with these measures in place.
Avoid direct sunlight on the e-Paper and take UV protection measures, as charged particles may dry out under prolonged intense light exposure, losing activity and becoming unable to refresh. This situation is irreversible.
On the white adhesive part of the e-Paper connection cable, use 3M tape to completely cover it. Complete coverage versus no coverage yields different reactions under UV light.
Place the e-Paper in a relatively shaded area, such as under tree shade or the shadow of an eaves.
When designing products with e-Paper, customers should ensure that the usage environment meets the requirements of the e-Paper.
Q: How many refresh cycles/lifespan does the e-Paper have?
Ideally, under normal use, it can be refreshed 1,000,000 times (1 million times).
Q: After using for a period, the screen refresh (full refresh) shows severe ghosting that cannot be fixed?
If the development board is powered on for a long time, it is recommended to set the screen to sleep mode or directly power it off after each refresh operation. Otherwise, the screen may be damaged if left under high voltage for an extended period.
Q: After the e-Paper enters deep sleep mode, can it be refreshed again?
Yes, but the e-Paper initialization operation needs to be performed again in software.
Q: Why is the displayed image shifted?
The SPI rate may be too high, causing data loss. Try reducing the SPI rate.
Insufficient power supply or unstable power may cause data loss.
Data lines that are too long can cause data loss. The extension cable should preferably not exceed 20cm.
Q: What is the waveform file of the e-Paper and what is its function?
The display grayscale of electrophoretic e-Paper is determined by the spatial position of particles within microcapsules or microcups. Black and white particles undergo electrophoresis under the influence of voltage. The voltage timing that drives this electrophoretic motion is the driving waveform of the e-Paper. The driving waveform is the core part of the e-Paper display; optimizing the driving waveform directly affects the display effect. The driving waveform file contains parameters that describe the voltage timing that causes particle electrophoresis and is called periodically during e-Paper refresh.
For different batches of e-Paper film, the electrophoretic matrix may require different voltage values for driving due to material, manufacturing processes, etc. This relationship between grayscale, voltage, and temperature is reflected in the e-Paper waveform. Generally, after each batch of electrophoretic matrix is produced, a corresponding waveform file is generated, existing as a .wbf file. The film manufacturer provides the waveform file and the electrophoretic matrix to the e-Paper screen manufacturer, who then integrates the protection board, substrate, and driver before providing it to the customer. If the waveform file does not correspond to the screen, it may result in no display or unsatisfactory display effects. Typically, the waveform file is OTP programmed into the e-Paper's driver IC at the factory, and some of our provided programs also call external waveform files to drive the e-Paper.
Q: What do LUT and OTP stand for?
LUT stands for LOOK UP TABLE, and OTP stands for ONE TIME PROGRAM. LUT essentially means loading the waveform file. Waveform files are of two types: OTP and REGISTER. OTP is an internal waveform storage method, while REGISTER is an external waveform storage method.
Q: What is the process of partial refresh for e-Paper?
There are mainly two types of e-Paper screens:
One type refreshes the background image first.
The other type alternately refreshes old data and new data.
Q: How to perform partial refresh simultaneously in different areas?
Performing partial refresh simultaneously in different areas requires programming: first, write the data for the different areas into the e-Paper IC, and finally perform a unified Updata/TurnOnDisplay.
Q: Does the raw screen product have a surface film when shipped?
Yes, it has a protective film.
Q: Does the e-Paper have a built-in temperature sensor?
Currently, all screens have a built-in temperature sensor. It is also possible to use the IIC pins to connect an external LM75 temperature sensor.
