This paper presents a low-cost solution to implement a functional test for RF ZigBee transmitter. More precisely, the objective is to enable symbol error detection for a 2.4GHz OQPSK-modulated signal with half sine pulse shaping on a digital ATE. The test is based on 1-bit under-sampled acquisition of the RF signal with a standard digital tester channel. A dedicated post-processing algorithm is then applied, which (i) extracts the phase information from the captured binary sequence, (ii) reconstructs the RF modulated signal and (iii) performs the demodulation. The different steps of the post-processing algorithm are detailed in this paper. Simulation and experimental results are presented, demonstrating the ability of the technique to correctly retrieve the emitted symbol sequence using only the binary data captured by the digital tester channel.