This repoistory includes the open source construction of the Volla Phone Plinius Plus to create accessory, that makes use of the pogo-PIN port.
See also the documentation of the device's kernel at https://github.com/HelloVolla/android_kernel_manifest/blob/volla-16.0-ansuz/docs/VPP_POGOPIN.md
Learn more about the device at https://volla.online/en/volla-phone-plinius/