Support for hardware SPI on NEC V25 port#2453
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ghaerr merged 5 commits intoghaerr:masterfrom Nov 13, 2025
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November 12, 2025 10:47
New driver for hardware SPI Mode 3 SD card interface using serial port 0 in synchronous IO mode. Baud rate can be configured in spi-hw-necv25.S default CPU clock/2. which is the fastest clock possible.
Added new option in config.in for CONFIG_HW_SPI if CONFIG_ARCH_NECV25 is selected
and renamed spi-8018x.h to spi.h
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Thank you @swausd, fantastic work as always! This is very nice having both software and hardware SPI drivers in ELKS! :) |
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ssd-sd block driver now supports hardware SPI on NEC V25 MCU or software SPI (bit-banged) on 8018x and NEC V25. Added new option
Interface SD card with hardware SPIinmake menuconfigifNEC V25system is selected. The bit banged driver should only be used if the serial port 0 is not available.The new hardware driver use SPI Mode 3 (hardware limit of V25) on serial port 0. Despite SD cards usually require SPI mode 0, the hardware driver in mode 3 works with all the different SD cards i have (3 different brands, two noname and sandisk compact extreme).
Clock is configurable by setting prescaler value in the driver code spi-hw-necv25.S. Default CPU
clock / 2which is the max clock usable. For my current system that is 5 MHz. With the bit-banged driver it is about 128KHz.I introduced two new assembler functions for block read/write and changed ssd-sd.c accordingly.
Minix filesystem should be used as this is much faster than FAT16.
For connecting the SD card and port usage see spi-hw-nev25.S and sp-necv25.S.