Matthias Blankertz
460a67cf9f
The builtin micropython SD card driver using the default micropython SPI implementation suffered from very low read speeds. Add an optimized SD card driver using rp2 PIO and DMA. Currently read only, write support to be added later. Signed-off-by: Matthias Blankertz <matthias@blankertz.org>
31 lines
846 B
C
31 lines
846 B
C
#pragma once
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#include <stddef.h>
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#include <stdint.h>
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inline static uint8_t sd_crc7(size_t len, const uint8_t data[const static len])
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{
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const uint8_t poly = 0b1001;
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uint8_t crc = 0;
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for (size_t pos = 0; pos < len; ++pos) {
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crc ^= data[pos];
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for (int bit = 0; bit < 8; ++bit) {
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crc = (crc << 1) ^ ((crc & 0x80) ? (poly << 1) : 0);
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}
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}
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return crc >> 1;
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}
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/* inline static uint16_t sd_crc16(size_t len, const uint8_t data[const static len]) */
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/* { */
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/* const uint16_t poly = 0b1000000100001; */
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/* uint16_t crc = 0; */
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/* for (size_t pos = 0; pos < len; ++pos) { */
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/* crc ^= data[pos] << 8; */
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/* for (int bit = 0; bit < 8; ++bit) { */
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/* crc = (crc << 1) ^ ((crc & 0x8000) ? poly : 0); */
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/* } */
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/* } */
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/* return crc; */
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/* } */
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