Arduino-Storage

The Storage library for Arduino is designed to abstract handling of external memory, and allow block read/write and streaming of data. The library includes device drivers for SPI SRAM (23LC512/1024), 2-Wire EEPROM (AT24CXX) and internal EEPROM.

Device driver for external storage such as EEPROM and SRAM should implement the Storage class virtual member functions and supply the number of bytes on the device.

The Storage class supports linear allocation. The Storage::Block class handles the allocated block and provides functions to read and write to the block.

In many cases the external block contains data that mirrors data used in the applications. The Storage::Cache handles read and write between the block on external storage and data/variables. The Storage::Cache class also allows handling of large vectors on external storage and element/member access.

Version: 1.0

Classes

• Abstract Storage Manager, Storage
• Storage Block, Storage::Block
• Storage Cache, Storage::Cache
• Storage Stream, Storage::Stream

Drivers

• 2-Wire EEPROM, AT24CXX
• 512 Kbit Serial SRAM, 23LC512
• 1 Mbit Serial SRAM, 23LC1024
• Internal EEPROM, EEPROM

Example Sketches

• Benchmarks measurement of characteristics.
• Block read/write eeprom blocks.
• Cache cache local variable.
• Persistent read/write configuration.
• Stream storage as a print stream.
• Vector handling large sample vectors.

Benchmarks

AT24C32, 2-Wire EEPROM, 100 KHz

Read

N	us	us/byte	kbyte/s
1	528	528.00	1.89
10	1352	135.20	7.40
100	9680	96.80	10.33
1000	93128	93.13	10.74

Write

N	us	us/byte	kbyte/s
1	408	408.00	2.45
10	1236	123.60	8.09
100	20540	205.40	4.87
1000	206280	206.28	4.85

Note: 1) The read/write operations have a three byte header (8-bit command, and 16-bit address). 2) Write performance increases up to page size. When the block size is larger than the page size the write operation will wait for the device to complete the page write. Typical max 5-10 ms per page. 3) 400 KHz (and even 800 KHz) clock can be used.

23LC1024, SPI SRAM, 8 MHz

Read

N	us	us/byte	kbyte/s
1	24	24.00	41.67
10	36	3.60	277.78
100	156	1.56	641.03
1000	1344	1.34	744.05

Write

N	us	us/byte	kbyte/s
1	24	24.00	41.67
10	36	3.60	277.78
100	172	1.72	581.40
1000	1468	1.47	681.20

Note: The read/write operations have a four byte header (8-bit command, and 24-bit address).

EEPROM

Read

N	us	us/byte	kbyte/s
1	4	4.00	250.00
10	16	1.60	625.00
100	112	1.12	892.86
1000	1072	1.07	932.84

Write

N	us	us/byte	kbyte/s
1	4	4.00	250.00
10	30780	3078.00	0.32
100	308140	3081.40	0.32
1000	3077476	3077.48	0.32

Note: The internal eeprom has a single byte buffer and write of multiple bytes will wait for the device to complete previous write. Typical 3 ms.

Dependencies

• Arduino-GPIO
• Arduino-TWI
• Arduino-SPI