SparkFun Thing Plus Dual-Port Logging Shield

• SparkFun Thing Plus Dual-Port Logging Shield
• Versatile dual-port logging shield for Thing Plus/Feather boards
• Fast read and write speeds up to 35 MBytes/second
• Supports FAT32, exFAT, and NTFS on cards up to 32GB
• Easy mode switching with simple I2C commands

The SparkFun Thing Plus Dual-Port Logging Shield is a Thing Plus/Feather-compatible board designed to enable access to a microSD card via both SPI and USB-C interfaces. This versatile shield can be mounted on or under a Thing Plus board, providing the ability to log data to and read data from the microSD card using a preferred Arduino SD library.

In addition to SPI access, the shield can be connected to a computer through a USB-C port, allowing for read and write speeds of up to 35 MBytes/second. The actual write speed is dependent on the card, but tests have shown speeds around 20 MB/s.

An ATtiny841 microcontroller on the shield serves as an arbiter, automatically switching the Dual-Port Logging Shield into SPI mode when the Thing Plus is powered up. This enables the Arduino code to access the microSD card as usual. When powered via USB-C from a computer, the ATtiny841 puts the shield into SDIO "thumb drive" mode, allowing for quick data transfer.

If both the Thing Plus and computer are connected simultaneously, the ATtiny841 can be given simple commands over I2C to switch between the two modes. The ATtiny can also be configured to default to either SPI mode or SDIO "thumb drive" mode when both power sources are active.

Please note that the USB2241, which provides the USB interface, supports FAT32, exFAT, and NTFS on cards up to 32GB. Cards larger than 32 GB are not supported.