A developer has implemented a single-bit analog-to-digital converter (ADC) on an STM32F407ZG microcontroller using GPIO and DMA, bypassing the need for a dedicated hardware ADC. The system uses a hardware timer to trigger DMA transfers, which read the state of the PA1 pin and store the logic levels in a RAM buffer.
The implementation involves configuring the GPIO port for input, setting the timer to a sampling frequency of 76.8 kHz, and using DMA2 Stream 1 Channel 7 to move data from the GPIO input register to memory. The process is designed to operate in the background, minimizing CPU load by triggering only one interrupt upon completion.
The setup is initiated by an external interrupt triggered by a negative voltage edge on the PA1 pin. This method allows for tasks such as software UART emulation, logic analysis, and data acquisition from multiple digital MEMS PDM microphones without impacting the performance of the main application.
Testing was conducted on a JL_32F4XX board, where the ADC successfully captured data from a UART2_TX signal. The developer noted that while this approach consumes more memory due to capturing 16-bit words for a single-bit signal, it enables efficient, non-blocking data stream monitoring.
