This circuit needs only four connections to equip a BASIC Stamp II with an LCD module.The BASIC Stamp II has 16 I/O lines. To connect an LCD module to a BASIC Stamp II board, you would need eight data lines and two control lines. Even if you split the data byte into two sequential four-bit packets, the LCD module still takes up six I/O connections of the BASIC Stamp board. With certain applications, this may mean that there are not enough I/O connections left over.Two bussesThe alternative control circuit described here makes do with only four leads. It employs the well-known 74HCT574 bus driver in an unconventional manner, as a serial-in, parallel out (SIPO) IC. As can be seen in Figure 1, the eight flip-flops of the bus driver are connected in series, so that it functions as a shift register. The serial input data reach the 74HCT574 via one lead (DATA), and a second lead (CLOCK) is required for the shift clock. The data traffic is similar to that on an I2C bus.