SparkFun Thing Plus Dual-Port Logging Shield
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We carry several data logging products which have microSD sockets on them: [OpenLog Artemis](https://www.sparkfun.com/products/16832) and the [Qwiic OpenLog](https://www.sparkfun.com/products /15164) to name but two. They\'re great for logging data to a microSD card, but when it comes to reading the logged data quickly you usually have to pop out the microSD card and plug it into your computer. But what if you\'re developing an embedded system and you don\'t want to or aren\'t able to eject the microSD card. Enter the SparkFun Thing Plus Dual-Port Logging Shield!
The SparkFun Dual-Port Logging Shield is a Thing Plus/Feather-compatible board which allows you to access your microSD card over both SPI and USB-C. It is designed to be mounted on or under one of our [Thing Plus boards](https://www.sparkfun.com/thing_plus). You can log data to and read data from your microSD card over SPI as usual, using your favorite Arduino SD library. But you can also connect it to your computer via USB-C and read and write files at up to 35 MBytes/second! The write speed is card-dependent but, in our tests, we\'ve routinely seen write speeds around 20MB/s.
The SparkFun Dual-Port Logging Shield has an ATtiny841 microcontroller on it to act as an arbiter: If you power up your Thing Plus, the ATtiny841 will automatically put the Dual-Port Logging Shield into SPI mode, so your Arduino code can access the microSD card as normal If you power the Shield from your computer by connecting it via USB-C, the ATtiny841 will put the Shield into SDIO \"thumb drive\" mode. Your computer can then read and write data really quickly! Finally, if you have both your Thing Plus powered up - and have your computer connected - then you can switch between the two modes by giving the ATtiny841 some very simple commands over I2C!
You can configure the ATtiny to automatically default to SPI mode or SDIO \"thumb drive\" mode if both power sources are powered up simultaneously. It\'s your choice!
**Note:** The USB2241, which provides the USB interface, supports FAT32, exFAT and NTFS on cards up to and including 32GB. Cards larger than 32GB are not supported.
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