DragonBoard 410c - How to Works the Low Speed ​​Expansion

About: Frederico Martins Pedroso Junior, 29 yo, Computer Engineer.

This tutorial is about the Low Speed Expansion on DragonBoard 410c. The Inputs and Outputs (I/O) of Low Speed Expansion on DragonBoard 410c are:

  • GPIO (General Purpose Input/Output);
  • MPP (Multi Purpose Pin);
  • SPI (Serial Peripheral Interface);
  • I2C (Inter-Integrated Circuit);
  • UART (Universal Asynchronous Receiver / Transmitter);
  • PCM (Pulse Code Modulation).

Step 1: Low Speed ​​Expansion - Schematic

Step 2: Pin Information - Ground

Step 3: Pin Information - Power Supplies

The DragonBoard 410c supports:


+1.8V:

Driven by two PMIC LDOs, LDO15 and LDO16, each can provide 55mA. The PM8916 allows connecting the two LDOs in parallel to provide 110mA on a 1.8V.

+5V:

Driven by the 4A 5.0V buck switcher (U13). This buck switcher powers both USB limit current devices (each at 1.18A max). The remaining capacity provides a max current of 1.64A to the Low Speed Expansion Connector, for a total of 8.2W.

SYS_DCIN:

Can serves as the board’s main power source or can receive power from the board.

Step 4: Pin Information - GPIO

The 96Boards specifications calls for 12 GPIO lines to be implemented on the Low Speed Expansion Connector. Some of these GPIOs may support alternate functions for DSI/CSI control. 11 GPIOs are routed to the APQ8016 SoC and one GPIO is connected to the on-board PMIC.

  • GPIO A (Pin 23)

Connects to GPIO_36 of APQ8016 SoC, can serves as AQP_INT supporting the 96Boards requirements to create a wake-up event for the SoC. It is a 1.8V signal.

  • GPIO B (Pin 24)

Connects to GPIO_12 of APQ8016 SoC. It is a 1.8V signal.

  • GPIO C (Pin 25)

Connects to GPIO_13 of APQ8016 SoC. It is a 1.8V signal. Can be configured to be an IRQ line.

  • GPIO D (Pin 26)

Connects to GPIO_69 of APQ8016 SoC. It is a 1.8V signal. Can be configured to be an IRQ line.

  • GPIO E (Pin 27)

Connects to GPIO_115 of APQ8016 SoC. It is a 1.8V signal. Can be configured to be an IRQ line;

  • GPIO F (Pin 28)

Connects to MPP_4 of PM8916 PMIC. It is a 1.8V signal. Can be configured to be the DSI backlight control.

  • GPIO G (Pin 29)

Connects to GPIO_24 of APQ8016 SoC. It is a 1.8V signal. Can be configured to be DSI VSYNC signal.

  • GPIO H (Pin 30)

Connects to GPIO_25 of APQ8016 SoC. It is a 1.8V signal. Can be configured to be a DSI_RST signal.

  • GPIO I (Pin 31)

Connects to GPIO_35 of APQ8016 SoC. It is a 1.8V signal. Can be configured to be a CSI0_RST signal.

  • GPIO J (Pin 32)

Connects to GPIO_34 of APQ8016 SoC. It is a 1.8V signal. Can be configured to be a CSI0_PWDN signal.

  • GPIO K (Pin 33)

Connects to GPIO_28 of APQ8016 SoC. It is a 1.8V signal. Can be configured to be a CSI1_RST signal.

  • GPIO L (Pin 34)

Connects to GPIO_33 of APQ8016 SoC. It is a 1.8V signal. Can be configured to be a CSI1_PWDN signal.

Step 5: Pin Information - I2C

  • The DragonBoard 410c implements I2C0 and I2C1 that connects directly to the APQ8016SoC;
  • A 2K resistor is provided as pull-up for each of the I2C lines per the I2C specifications, these pull-ups are connected to the 1.8V voltage rail.

Step 6: Pin Information - SPI

  • The DragonBoard 410c implements a full SPI master with 4 wires, CLK, CS, MOSI and MISO all connect directly to the APQ8016 SoC;
  • These signals are driven at 1.8V.

Step 7: Pin Information - UART

  • The DragonBoard 410c implements UART0 as a 4-wire UART that connects directly to the APQ8016 SoC. These signals are driven at 1.8V;
  • Implements UART1 as a 2-wire UART that connects directly to the APQ8016 SoC. These signals are driven at 1.8V.

Step 8: Pin Information - PCM/I2S

  • The DragonBoard 410c implements a PCM/I2S with 3 wires, CLK, FS and DO, the optional DI signal is not implemented on the DB410c.
  • The I2S signals are connected directly to the APQ8016 SoC. These signals are driven at 1.8V.

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