@woodster I have managed to find this article in Japanese which Google translated nicely for me: https://slanew.com/news/612

All working now - so hopefully this will help other people trying to do the same :)

I have an M5StickC and have tried to get it to work with the Mini GPS/BDS Unit (AT6558), link to product: https://m5stack-store.myshopify.com/products/mini-gps-bds-unit?_pos=1&_sid=fd2c01a5a&_ss=r

I know it's meant for the M5 Core but I thought with it having a standard grove port it might work. Is this is the problem that that the functionality of the port differs between models?