Raspberry Pi Zero 3 W and Pi 4 Model A Device Trees Appear

Device tree files for a Raspberry Pi Zero 3 W and a Raspberry Pi 4 Model A have appeared in Raspberry Pi's Linux kernel tree, with Phoronix spotting the change first, according to Bret. Neither board is officially announced, but both appear to use the Broadcom BCM2711 SoC from the Raspberry Pi 4. The details come from device tree interpretation, so final hardware may differ.

Zero 3 W uses the BCM2711 SoC

The Zero 2 W launched almost exactly five years ago, so a successor has been overdue. The Zero 3 W device tree names the Broadcom BCM2711, the same quad-core Cortex-A72 chip as the Raspberry Pi 4, replacing the Zero 2 W's quad-core 1GHz Cortex-A53 RP3A0. Clock speeds are not stated, and the BCM2711 may run hot in the smaller footprint. The storage controller is configured with an 8-bit bus width and a comment about 'the eMMC/SD card', which only really makes sense for eMMC, though the author expects microSD on the final board because eMMC would raise the price. GPIO names include SPI flash lines, suggesting the same EEPROM-based bootloader as the Pi 4; the Zero 2 W never had one. That should bring Pi 4 boot options and bootloader updates. The board also appears to have one HDMI output, a power button defined on GPIO 46 and mapped to KEY_POWER, Wi-Fi and Bluetooth like the BCM2711 family, one ACT LED, and the usual 40-pin GPIO layout, so existing HATs should be fine.

More speculative details include an enabled PCIe controller, lines named PCIE_PWR_EN and PCIE_DET_WAKE, and a 4-lane CSI camera configuration rather than the Pi 4 Model B's 2-lane one. Both device trees share copy-and-paste DNA, including a duplicated 'PWR_GPIO' line name, so those points should not be overread.

Pi 4 Model A strips back the Model B

There has not been a Model A since the Raspberry Pi 3 Model A+ in 2018. The Pi 4 Model A appears to follow the familiar formula: remove features such as Ethernet and some USB ports, then lower the price. Its Ethernet controller is not enabled, and GPIO lines used for the Ethernet PHY on the Model B are repurposed. It has one HDMI output instead of two micro HDMI ports, no 3.5mm audio or composite jack, and microSD only with the same 1.8V signalling support as the Model B. Audio will be over HDMI, USB or I2S.

External antenna support may be the most interesting addition. There are two antenna control lines, ANT_CTRL1 and ANT_CTRL2, and overlay parameters named ant1, ant2 and noant, matching how the Compute Module 4 switches between onboard and external U.FL antennas. The board also has PWR and ACT LEDs, the same SPI flash bootloader setup as the Model B, and the same power button definition as the Zero 3 W. USB is not described; USB 3 is possible because the PCIe controller is enabled, but the previous Model A+ had one USB-A port and that may be expected again.

RAM, pricing and release date are unknown

Device trees do not describe RAM, and there is no word on memory configurations, pricing, clock speeds, connector types or a release date. A lower-cost Pi 4 variant makes sense while memory costs are high, and the mature BCM2711 is well supported in software. The Zero 3 W is harder to judge because the Zero range depends on price, and the BCM2711 may cost more to build around than the RP3A0. Kernel support landing ahead of launch is usually a good sign that hardware is not far off, and the author plans to add both boards to sbc.compare. Everything above comes from device tree files, not an official spec sheet.

Sources: bret.dk