Here's one version of our family Idli podi recipe taken from my grandma's diary. Basically this podi is made with Whole Black gram with skin on, but ran out of those in my pantry and had to go with split black gram.
Idli Podi / Gun Powder / Karam Podi / Poondy Milagai Podi / Thengai Podi / Dosai Milagai Podi / Spice Powder / Idli Powder / Kaara Podi / Garlic Milagai Podi