5.1 microSD Card Settings

Some microSD cards work only with slew rate on and drive strength high settings. To address this issue, the PIO I/O Slewrate Control register and the PIO I/O Drive register 1 need to be set as follows.

PIO I/O Slewrate Control Register
  • Name: PIO_SLEWR
  • PIOA Slewrate Address: 0xFFFFF510 (0xFFFFF400 PIOA Base Address + 0x0110 Slewrate Offset)
  • Value to be bitwise OR-ed: 0x0000003F
PIO I/O Drive Register 1
  • Name: PIO_DRIVER1
  • PIOA Drive Strength Address: 0xFFFFF518 (0xFFFFF400 PIOA Base Address + 0x0118 Drive Strength Offset)
  • Value to be bitwise OR-ed: 0x0000003F

For Linux applications, the SAM9X75-Curiosity board device tree initiates the pin control settings accordingly.

For bare metal applications, the bootstrap is configured with drive high and slew rate on settings.

When using MPLAB X, these settings can be configured in the Pin Settings section of Harmony 3 Configurator as shown below.

Figure 5-1. Harmony 3 Configurator ‘Pin Settings’ Section

Affected Curiosity Kit:

SAM9X75-Curiosity