SD SPI vs SDMMC

Status	Not started / In progress / Complete
Impact	High / Medium / Low
Driver
Approver
Contributors
Informed
Due date
Resources

Relevant data

Background

Options considered

	Option 1	Option 2

Option 1

Option 2

Description

SD via SPI

SD SDMMC

Pros and cons

Protocol that FW is familiar with

Fewer physical pins

Uses a SPI port that could be used for something else

Built in data validation & redundancy

Harder to write FW for ('non-standard')

SDMMC Packet Overhead: 48 bits from host, 48 bits from SD card, 16 bits

Estimated cost

Large

Medium

Action items

Determine logging output rate

Determine loop control rate @Aidan Bowers (Deactivated) (100-200Hz)

How much data in bytes we expect to log @Dhruv Upadhyay

SD Packet Overhead:

Timing requirement for how long the transaction can take @Dhruv Upadhyay

Determine what factors impact SD SPI transmission rates @Darwin Clark

Outcome

If data rates are similar, having a dedicated peripheral opens up the board to greater flexibility in the future. It is believed that sdmmc is faster than sd using spi. The firmware development cost is unknown in both scenarios, and is estimated to be similar for both. It is known that additional firmware will not need to be written for data validation when using sdmmc. For these reasons, it is suggested that sdmmc is used.