SD SPI vs SDMMC

Owned by Aidan Bowers (Deactivated), created
Last updated: 2022-09-18 by Anonymous
1 min read

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.

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