2024-10-08(6): Project/Peripherals/Cross

Cross Development Recap

• Cross Development

• Cross Toolchain Setup

• CMake: Cross Build

Project Kickoff: Hack Hardware In Groups

Devices Overview

• Proximity Sensor: VL53L1X

• Gyroscope (BNO055)

• Motor Control: BTN9960LV

• Motor Control: Servo Motor

Linux And I2C

• Enable I2C on Raspi

  • Enable I2C, and Check (Bootloader config, /boot/config.txt)

  • Verify That Our Device Is There (i2cdetect)

• Userspace I2C, /dev/i2c-1, ic2-dev and SMBus:

  • Kernel documentation: https://docs.kernel.org/i2c/dev-interface.html

  • Example using LM73 temperature sensor: Implementing A LM73 Client In Userspace

Linux And PWM

• PWM Userspace Interface (using PCA9685)

Linux And SPI

• ws2812-spi on Github. Look into ws2812/spi.cpp:

  struct spi_ioc_transfer tr = {
      .tx_buf = (unsigned long)xfer_bytes,
      .len = (uint32_t)xfer_size,
      .speed_hz = s.profile().frequency_hz,
  };
  
  int ret = ioctl(_fd, SPI_IOC_MESSAGE(1), &tr);
  

• https://datasheets.raspberrypi.com/bcm2711/bcm2711-peripherals.pdf

  Things to take into accout when you use SPI to clock out multi-byte waveforms. Take care of “2.3.1. SPI implementation details”, where they say that there is a garanteed gap between two bytes. During that time the MOSI signal is also low (alas it’s SPI).