RTLPlayground/doc/mods.md

Modifications

SPI-Flash Memory

SPI-Flash memory can be replaced with an other type. Because the chip is defect, like #69 & #70 or you have an unmanaged-switch with a small flash size, and want to convert it to a managed-variant to run RTLPlayground software on it. Currently RTLPlayground-firmware expects 8 MBit / 1 MiB.

Size

The SOC (RTL837x network chip) used 24-bit address to access the device. This means that in theory, a memory size up to 2^24 x 8-bit = 16777216 x 8-bit = 128 MBit or 16 MiB could be used, this is untested!

Speed

The SOC (RTL837x network chip) is connected via an SPI-BUS to the flash memory. SPI-BUS frequency is 62.5 MHz. Look in the datasheet for AC Electrical Characteristics and lookup symbol Fr. Maximum value should be equal or higher than 62.5 MHz. A device that supports the highest possible clock speed is not a better device, nor is the SOC going to run faster. So pick one which have common frequency between 80 MHz to 133 MHz. Memory speed is dictated by the SPI-BUS clock frequency which is 62.5 MHz.

SPI Operation

By default, SPI-BUS uses CLK, CS, DI and DO. To increase the data throughput without increasing the bus frequency, a single command can run in DUAL SPI operation. This means that for a specific command DI and DO are both used to transfer the data to/from the device. So it makes the data transfer up-to twice as fast. Although the SOC datasheet doesn’t mention it, our software is making use of this mode.

Package

Most use package are SO8-type may also called SOIC8-type. Which can also have different width. Like 150-mil, 208-mil or 300-mil. Best to measure what you need and confirm the measurement with the device-datasheet.

Specification

1. Size: At least 8 MBit / 1 MiB (theoretic max. 128 MBit / 16 MiB, but is not tested!)
2. Speed: 62.5 MHz or better.
3. Support for DUAL SPI operation. Device need support for command BBh, Dual I/O Fast Read or Fast Read Dual I/O.

Known Working

This list is incomplete.

Brand	Partnumber
GigaDevice	GD25Q32E
Fundan	FM25Q16A
Puya	P25D40SH
Winbond	W25Q16JV
Winbond	W25Q32FV
Winbond	W25Q32JV
Winbond	W25Q16JL
Winbond	W25Q16DV
Winbond	W25Q80DV

NOTE: Part numbers are incomplete. Part numbers may contain additional information such as package, temperature specifications, and even the number of devices on a reel. So always check the datasheet so that you have the right orderable partnumber.