Hello everyone,
I’d like to show you a project I’m working on. It actually grew out of another project, but that’s another story.
This one is inspired by the Pandora and Pyra handhelds. They’re nice devices, but there are a few issues: they aren’t really available anymore, and their hardware is no longer very powerful. So, I wanted something similar but with more power
So I wanted something similar, but with more power. And this power is provided by a Raspberry Pi CM4/CM5.
The design is meant to be similar to the aforementioned handhelds. The display will be either a 4.3-inch or 5-inch panel from BuyDisplay (needs to be decided which exactly), with a resolution of 800×480. For the 5-inch option, a 720×1280 panel is possible, but it’s in portrait orientation—and non-portrait versions are hard to find. To keep the design mod-friendly, the display driver IC won’t be on the mainboard. Instead, it will be on a separate board in the display lid, because 800×480 display have most of the time an RGB interface, while the 720×128 displays use MIPI.
The mainboard features the BQ24292I for battery management (the same IC used in the Retro Lite CM4). A couple of voltage regulators will supply the necessary voltages for both the Raspberry Pi and the microcontroller.
The MCU will be the RP2040. While there are more efficient MCUs out there, the RP2040 is easy to develop for and can be flashed via USB without needing an extra bootloader. Alternatively I could change it to a STM32F103. I worked with them in the past, but I only had problems with them when trying to flash them via serial or USB. Only with a ST-Link V2 it flashed without problems. The MCU will handle the keyboard, mouse, gamepad, some functions of the CM4/CM5 like the power button for example and has the option to support a touchscreen via an I2C controller.
The keyboard matrix will reside on a separate board.
For the thumbsticks, I initially wanted to use the N40P107 from the Pyra, but they’re no longer available. Worse yet, there’s no suitable replacement. The flattest joystick I’ve found is the YTL YHE-YG19-008 SR2B166A1, which looks like a clone of the Nintendo Switch sticks. These are available on LCSC, which I consider more reliable than random sources (e.g., AliExpress). The joystick will also serve as the mouse.
For audio, I’m using the PCM5122, a I2S DAC.
Regarding ports, there will be:
-Two USB 2.0 ports
-One USB 3.0 port (when a CM5 is used and the USB3 pads are closed)
-One USB-C port in device mode and for charging
-One HDMI output
-One Ethernet port
-One headphone jack
-A pin-socket header for serial
-I'm also thinking of adding a header with a few GPIO Pins
-Internally, there will be a connector that combines the PCIe lane with a USB 2.0 line for future expansions (like storage or a 4G/5G Modem).
For storage, there will be two microSD card slots. One is intended for the operating system—though it won’t be used if the CM4/CM5 has onboard eMMC. The second slot is connected to the Pi via SDIO (through GPIO pins). There will also be a configuration EEPROM on board.
I attach the schematic because I don't know if I wired the Pi correct and for your feedback, if there is something I can improve.
I’d like to show you a project I’m working on. It actually grew out of another project, but that’s another story.
This one is inspired by the Pandora and Pyra handhelds. They’re nice devices, but there are a few issues: they aren’t really available anymore, and their hardware is no longer very powerful. So, I wanted something similar but with more power
So I wanted something similar, but with more power. And this power is provided by a Raspberry Pi CM4/CM5.
The design is meant to be similar to the aforementioned handhelds. The display will be either a 4.3-inch or 5-inch panel from BuyDisplay (needs to be decided which exactly), with a resolution of 800×480. For the 5-inch option, a 720×1280 panel is possible, but it’s in portrait orientation—and non-portrait versions are hard to find. To keep the design mod-friendly, the display driver IC won’t be on the mainboard. Instead, it will be on a separate board in the display lid, because 800×480 display have most of the time an RGB interface, while the 720×128 displays use MIPI.
The mainboard features the BQ24292I for battery management (the same IC used in the Retro Lite CM4). A couple of voltage regulators will supply the necessary voltages for both the Raspberry Pi and the microcontroller.
The MCU will be the RP2040. While there are more efficient MCUs out there, the RP2040 is easy to develop for and can be flashed via USB without needing an extra bootloader. Alternatively I could change it to a STM32F103. I worked with them in the past, but I only had problems with them when trying to flash them via serial or USB. Only with a ST-Link V2 it flashed without problems. The MCU will handle the keyboard, mouse, gamepad, some functions of the CM4/CM5 like the power button for example and has the option to support a touchscreen via an I2C controller.
The keyboard matrix will reside on a separate board.
For the thumbsticks, I initially wanted to use the N40P107 from the Pyra, but they’re no longer available. Worse yet, there’s no suitable replacement. The flattest joystick I’ve found is the YTL YHE-YG19-008 SR2B166A1, which looks like a clone of the Nintendo Switch sticks. These are available on LCSC, which I consider more reliable than random sources (e.g., AliExpress). The joystick will also serve as the mouse.
For audio, I’m using the PCM5122, a I2S DAC.
Regarding ports, there will be:
-Two USB 2.0 ports
-One USB 3.0 port (when a CM5 is used and the USB3 pads are closed)
-One USB-C port in device mode and for charging
-One HDMI output
-One Ethernet port
-One headphone jack
-A pin-socket header for serial
-I'm also thinking of adding a header with a few GPIO Pins
-Internally, there will be a connector that combines the PCIe lane with a USB 2.0 line for future expansions (like storage or a 4G/5G Modem).
For storage, there will be two microSD card slots. One is intended for the operating system—though it won’t be used if the CM4/CM5 has onboard eMMC. The second slot is connected to the Pi via SDIO (through GPIO pins). There will also be a configuration EEPROM on board.
I attach the schematic because I don't know if I wired the Pi correct and for your feedback, if there is something I can improve.
