Ups, better not use D17, D16
On D2WD, pins GPIO16, GPIO17, SD_CMD, SD_CLK,
SD_DATA_0, SD_DATA_1 are used to connect the built-in SPI Flash chip. Using them for some other purpose will interfere with code execution from flash, leading to illegal instruction exception. Also note that D2WD uses a 1.8V flash chip, so all pins in VDD_SDIO domain use 1.8V supply voltage.