Hi, I haven't found any specific documentation but looking in the MYSBootloader's code I found this two checks in HW.h (https://github.com/mysensors/MySensorsBootloaderRF24/blob/development/HW.h) #if defined(SPI_PINS_CE9_CSN10) .. #elif defined(SPI_PINS_CSN7_CE8) .. #endif does it mean that those PINs (9+10 or 7+8) are the only options to have MYSBootloader on Arduino boards? (obviously without modifying the code and recompiling..) thanks Max