We propose an adaptation of the well-known Time Slotted Channel Hopping (TSCH) Medium Access Control (MAC) protocol, which was initially specified for IEEE 802.15.4 based networks, for operation over the LoRa PHY layer. Thanks to its deterministic nature, multiple concurrent communications can be handled, while reducing channel collision and ensuring reliability in a power-efficient manner. The proposed solution was implemented in the Contiki-NG operating system and tested on real motes.