Hi all,
I would like to estimate the following equation:

Y = b0 + b1T + X*beta + U1 (1)

where T is a binary variable and Y is a discrete variable (1 to 4); and U1 is an error term. The variable T is endogenous and I have two discrete instrumental variables Z1 and Z2. So, the first stage equation is:

T = Z*gamma + X*theta + U2 (2)

I wonder if I can use the control function approach to estimate equations (1) and (2)? Or does someone have another approach that I can use to have consistent estimates?

Thanks in advance.