Here's something new from the DIY lab. After receiving an email advertising China displays, I was notified by Elecrow that CrowPanel 4.2 It's an open-source ePaper display based on the ESP32-S3 and uses the same 4.2" display as the original OBP60. It also features a jog dial, two buttons, and an SD card adapter. The CrowPanel 4.2 is extremely simple and very low-cost. It costs just €28.61. The board is single-sided. The display is glued to the back. Three laser-cut Plexiglas panels form the housing, held together with four screws. I love this type of construction because it's reduced to the absolute minimum.
Fig.: CrowPanel 4.2 (Elecrow)
Fig. Circuit board (Elecrow)
Fig. back (Elecrow)
The CrowPanel 4.2 is powered by a 5V USB-C port. There's also a socket for a LiPo battery, which can be used to power the display independently. A 20-pin header on the top edge connects to a few GPIOs and the 3.3V power supply.
Overall, the display is ideal as a gateway for testing or simple applications below deck, where the display isn't exposed to harsh conditions. Because the OBP60 firmware is modular, it was easy to adapt to the CrowPanel 4.2 firmware. After four hours of work, the display was up and running and displaying initial data.
In principle, the display can be used to display all bus data if you use a bus-capable device such as the OBP60 or an M5Stack Atom with firmware that includes the NMEA 2000 gateway. The data is then transferred to the CrowPanel 4.2 via a Wi-Fi connection, where it can be displayed as usual with the OBP60. This allows you to build an instrument display for the chart table, for example, so you always have all the data at a glance. If you want, you can even use two displays simultaneously.
However, there are also some limitations for the OBP40:
- No waterproof housing
- No outdoor use possible
- No 12V supply
- No protective plexiglass panel in front of the display
- No sunscreen filters
- Power supply only possible via USB-C
- No display lighting
- Only a limited number of buttons (Up, Down, Push, Menu, Exit)
- No swipe gestures
- No flash LED and no buzzer
- No physical bus interfaces to NMEA0183, NMEA2000
- No I2C, 1Wire (but are on the socket header)
- No real-time clock
- No GPS
- No environmental sensor
The CrowPanel 4.2 is only 8.5 mm thick and extremely inexpensive to purchase. I had already considered a simplified indoor version of the OBP60. The development effort was initially too high for me, as I hardly have time to create anything new. With the CrowPanel 4.2, Elecrow has done the work for me, and the display can be used directly for such applications.
But its primary purpose is to familiarize yourself with the OBP60's functions. It's also very convenient for software development, as the display can be connected directly to the USB port of a laptop or PC. I've added this lightweight hardware version to the OBP60's firmware. Other hardware versions will be added later. I already have some ideas.
Fig.: OBP40 different views
I didn't find the USB-C power supply particularly suitable for a boat application, as the cable exits the side and is visually distracting. Furthermore, the display can't be powered directly with 12V. I also constructed my own housing into which the disassembled display can be inserted. If you then add a small Mini DC/DC converter glued to the circuit board, you can also supply the display with 12V. I made the case a bit larger so that the SD card, which sticks out a bit, disappears inside the case. Visually, the case of the OBP40 is matched to the case of the original OBP60. This means it fits harmoniously into the overall picture. I also took the opportunity to try out two-color printing on my Bambu Lab printer. It works really well and I don't have to print multiple parts. The black areas are 0.4 mm thick inserts (2 layers) in the front. The colors blend seamlessly into one another and you can't feel any transition.
On the back of the OBP40 is a magnetic 4-pin pogo pin adapter, allowing the display to be powered by a small 1200 mAh LiPo battery and charged via USB. An additional voltage divider allows the battery voltage to be measured. If the battery voltage is too low, the OBP40 shuts down automatically. A charging cradle with a holder is also included. This allows the display to be used on the move or to exchange NMEA 0183 data via USB. The display can also be programmed using the pogo pins.
The OBP40 with the Crow Panel 4.2 is fully integrated into the OBP60 firmware. All software functionality is therefore also available in the OBP40. Using appropriate compiler flags, firmware for the OBP40 can be created. The repository is located on GitHub at the following link:
There is also an extensive multilingual Documentation for the OBP40 which describes all the special features in detail. It describes how to convert the Crow Panel 4.2 into an OBP40. Configuration examples make getting started easier and contribute to successful project implementation.
In the Elecrown's Wiki for CrowPanel 4.2 You can find all the documentation and some useful software examples with which you can test the hardware. For example, there is also software with which you can transfer content to the display via Bluetooth or WiFi. This could theoretically transfer any content to the display, such as weather data, emails, reminders, or other useful information. This was originally intended for use in meeting rooms or as a sign for price marking. There is also a weather demo with which the local weather forecast can be retrieved from the Internet and displayed. Theoretically, any custom application could also be written for the CrowPanel 4.2. In principle, other ePaper displays from Elecrown could also be integrated into the firmware. There are also smaller or larger display. You just have to make sure that you use a display controller that is supported by the GxEPM2 library.
I think the OBP40 is a good addition to the OBP60. It's an affordable entry-level solution and a great way to familiarize yourself with the technology. The display also lends itself to more advanced projects if you include the unused GPIOs. Then you could also connect to NMEA2000 or NMEA0183, or use sensors on the I2C or 1Wire bus. The sky's the limit. The SD card allows for other cool features like weather or data logging.