Get BlinkM version or address with Basic Stamp

I am having trouble retrieving the BlinkM address and version info using a Basic Stamp:
The address comes back as 255.

Sending commands work fine.

BlinkMAddress: 'doesn't work
GOSUB I2C_Start
I2C_data = DeviceAddr << 1 ' shift left because address is upper 7 bits
GOSUB I2C_Send
I2C_data = "a"
GOSUB I2C_Send
IF (I2C_ack = Nak) THEN BlinkMAddress ' wait until not busy
I2C_ack = Nak
I2C_data = 0
SHIFTIN SDA, SCL, MSBPRE, [I2C_data\8]
SHIFTOUT SDA, SCL, LSBFIRST, [I2C_ack\1] ' send ack or nak
DEBUG "Address: ", DEC I2C_data, CR
GOSUB I2C_Stop
PAUSE 1
RETURN

'Send Address or Data Procedure
I2C_Send:
SHIFTOUT SDA, SCL, MSBFIRST, [I2C_data] '[I2C_data\8] 'Send Byte To Device
SHIFTIN SDA, SCL, MSBPRE, [I2C_ack\1] '[I2C_ack\1] ' Get Acknowledge Bit
RETURN

' -----[ Low Level I2C Subroutines]----------------------------------------
I2C_Start: ' I2C Start Bit Sequence
INPUT SDA
INPUT SCL
LOW SDA ' SDA --> Low While SCL High
RETURN

I2C_Stop: ' I2C Stop Bit Sequence
LOW SDA
INPUT SCL
INPUT SDA ' SDA --> High While SCL High
RETURN