Portable SDR using STM32F7-Discovery board and RTLSDR USB receiver.

We want to make a low-cost RF spectrum analyzer / receiver using an RTL-SDR compatible dongle connected to an STM32F7-Discovery board. The goal is to demonstrate the DSP capabilities of the STM32F7 processor and the usage of the USB Host Middleware in STM32 Cube to implement a custom class.

The project is developed using the free, Eclipse-based IDE called System Workbench for STM32 (SW4STM32). To set-up the IDE you should follow the instructions of the site. I used Eclipse Neon for C/C++ developers under Ubuntu 16.04.

• USBH driver is able to recognize and enumeate RTL-SDR
• Manipulating RTL2832 registers with USB Control Transfers working
• USBH driver was modifed to be able to deal with Stalled Control Transfers, that may arise while recognizing the RTL-SDR tuner chip by I2C.
• Tuner chip recognition (probing) is working.
• Elonics E4000 tuner driver is working.
• The data samples from RTLSDR are successfully copied to a SDRAM buffer.

• Use DMA for speeding up the data transfers from EP1 (samples)
• Perform some FFT on the samples to check what we are receiving.
• Check the correct operation of E4K_tune_freq
• Implement/Port other tuners from librtlsdr.

• STM32F7-Discovery Evaluation Board
• RTL-SDR compatible USB dongle
• Micro USB to USB OTG Adapter Cable (Look for in eBAY)
• External 5V power supply to STM32F7-Discovery.

• Linux standard build system (Make)
• GNU ARM Compiler Toolchain
• OpenOCD (properly patched for STM32F7)

The STM32F7-Discovery board connected to an RTL-SDR dongle was found to draw a total current of approximately 650mA. This is beyond the limit of current that can be provided by a standard USB 2.0 port (500mA). Therefore an external 5V power supply must be attached to JP2. In addition, the JP1 jumpers must be set as follows:

• JP1 5Vext: ON
• JP1 5Vlink: OFF
• JP1 USB_FS: OFF
• JP1 USB_HS: OFF