I'm using teacup firmware for 3d printing, and im using the cnc sheild v3 board. I'm having trouble adding a heater on the configtool. I tried adding a heater like my fan and heatbed but i couldnt select the pin I'm using. Usually when i click on "pin" (to select the pin im using), there are options. but when I go to add a heater, there are no options or a way to type in the pin. (I have extra pins which are not being used, so its not like i used up all my pins and have no more.) how should I select the pin? Thanks in advance. Please reply asap. Thanks again.