Orthogonal Frequency Division Multiplexing (OFDM) has been applied to LED visible light communication in combination with low-frame-rate CMOS image sensor to achieve high-bitrate multiple-access communication. In order to improve the OFDM multiplexing/de-multiplexing accuracy, FPGA-based all digital signal processing techniques are used for visible light communication with low-frame-rate CMOS image sensor. Pulse width modulation is used for LED intensity modulation and number of white pixels on the LED image is counted for direct detection with 30-fps CMOS image sensor as all the digital signal processing techniques. Correlation coefficients and constellation diagram of QPSK-OFDM in 16-subcarriers spaced 0.1 Hz apart are experimentally evaluated.