The current massive use of digital communications demands a secure link by using an embedded system (ES) with data encryption at the protocol level. The serial peripheral interface (SPI) protocol is commonly used by manufacturers of ESs and integrated circuits for applications in areas such as wired and wireless communications. We present the design and experimental implementation of a chaotic encryption and decryption algorithm applied to the SPI communication protocol. The design of the chaotic encryption algorithm along with its counterpart in the decryption is based on the chaotic Hénon map and two methods for blur and permute (in combination with DNA sequences). The SPI protocol is configured in 16 bits to synchronize a transmitter and a receiver considering a symmetric key. Results are experimentally proved using two low-cost dsPIC microcontrollers as ESs. The SPI digital-to-analog converter is used to process, acquire, and reconstruct confidential messages based on its properties for digital signal processing. Finally, security of the cryptogram is proved by a statistical test. The digital processing capacity of the algorithm is validated by dsPIC microcontrollers.