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Copy bios device functions to kernel

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This commit is contained in:
Byron Lathi
2023-09-04 14:31:55 -07:00
parent 791bffb248
commit a770d938de
12 changed files with 1071 additions and 0 deletions
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10
sw/kernel/devices/board_io.h Normal file
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#ifndef _BOARD_IO_H
#define _BOARD_IO_H
#include <stdint.h>
uint8_t sw_read();
void led_set(uint8_t val);
#endif

24
sw/kernel/devices/board_io.s Normal file
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.include "io.inc65"
.importzp sp, sreg
.export _sw_read
.export _led_set
.autoimport on
.code
; @out A: The Value of the switches
; Reads the current values of the switches.
_sw_read:
lda SW
ldx #$0
rts
; @in A: val
; @out A: 0 for success, 1 for failure
; Sets the LEDs
_led_set:
sta LED
rts

15
sw/kernel/devices/interrupt.h Normal file
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#ifndef _INTERRUPT_H
#define _INTERRUPT_H
#include <stdint.h>
#define BUTTON (1 << 0)
#define UART (1 << 1)
void irq_int();
void nmi_int();
uint8_t irq_get_status();
void irq_set_status(uint8_t);
#endif

51
sw/kernel/devices/interrupt.s Normal file
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; ---------------------------------------------------------------------------
; interrupt.s
; ---------------------------------------------------------------------------
;
; Interrupt handler.
;
; Checks for a BRK instruction and returns from all valid interrupts.
.import _handle_irq
.import _cputc, _clrscr
.export _irq_int, _nmi_int
.include "io.inc65"
.segment "CODE"
.PC02 ; Force 65C02 assembly mode
; ---------------------------------------------------------------------------
; Non-maskable interrupt (NMI) service routine
_nmi_int: RTI ; Return from all NMI interrupts
; ---------------------------------------------------------------------------
; Maskable interrupt (IRQ) service routine
_irq_int: PHX ; Save X register contents to stack
TSX ; Transfer stack pointer to X
PHA ; Save accumulator contents to stack
INX ; Increment X so it points to the status
INX ; register value saved on the stack
LDA $100,X ; Load status register contents
AND #$10 ; Isolate B status bit
BNE break ; If B = 1, BRK detected
; ---------------------------------------------------------------------------
; IRQ detected, return
irq: PLA ; Restore accumulator contents
PLX ; Restore X register contents
jsr _handle_irq ; Handle the IRQ
RTI ; Return from all IRQ interrupts
; ---------------------------------------------------------------------------
; BRK detected, stop
break:
pla
plx
rti

439
sw/kernel/devices/sd_card.c Normal file
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#include <conio.h>
#include "sd_card.h"
#include "sd_print.h"
#include "spi.h"
/*******************************************************************************
Initialize SD card
*******************************************************************************/
uint8_t SD_init()
{
uint16_t i;
uint8_t res[5], cmdAttempts = 0;
SD_powerUpSeq();
while((res[0] = SD_goIdleState()) != SD_IN_IDLE_STATE)
{
cmdAttempts++;
if(cmdAttempts == CMD0_MAX_ATTEMPTS)
{
cputs("Go IDLE\r\n");
return SD_ERROR;
}
}
for (i = 0; i < 1000; i++);
SD_sendIfCond(res);
if(res[0] != SD_IN_IDLE_STATE)
{
cputs("IF Cond\r\n");
return SD_ERROR;
}
if(res[4] != 0xAA)
{
return SD_ERROR;
}
cmdAttempts = 0;
do
{
if(cmdAttempts == CMD55_MAX_ATTEMPTS)
{
cputs("op_cond error\r\n");
return SD_ERROR;
}
res[0] = SD_sendApp();
if(SD_R1_NO_ERROR(res[0]))
{
res[0] = SD_sendOpCond();
}
for (i = 0; i < 1000; i++);
cmdAttempts++;
}
while(res[0] != SD_READY);
for (i = 0; i < 1000; i++);
SD_readOCR(res);
return SD_SUCCESS;
}
/*
// Send a command with starting end ending clock pulses
uint8_t res1_cmd(uint8_t cmd, uint32_t arg, uint8_t crc)
{
uint8_t res1;
// assert chip select
spi_exchange(0xFF);
spi_select(0);
spi_exchange(0xFF);
// send CMD0
SD_command(cmd, arg, crc);
// read response
res1 = SD_readRes1();
// deassert chip select
spi_exchange(0xFF);
spi_deselect(0);
spi_exchange(0xFF);
return res1;
}
*/
/*******************************************************************************
Run power up sequence
*******************************************************************************/
/*
void SD_powerUpSeq()
{
uint16_t i;
uint8_t j;
// make sure card is deselected
spi_deselect(0);
// give SD card time to power up
for (i = 0; i < 1000; i++);
// select SD card
spi_exchange(0xFF);
spi_deselect(0);
// send 80 clock cycles to synchronize
for(j = 0; j < SD_INIT_CYCLES; j++)
spi_exchange(0xFF);
}
*/
/*******************************************************************************
Send command to SD card
*******************************************************************************/
/*
void SD_command(uint8_t cmd, uint32_t arg, uint8_t crc)
{
// transmit command to sd card
spi_exchange(cmd|0x40);
// transmit argument
spi_exchange((uint8_t)(arg >> 24));
spi_exchange((uint8_t)(arg >> 16));
spi_exchange((uint8_t)(arg >> 8));
spi_exchange((uint8_t)(arg));
// transmit crc
spi_exchange(crc|0x01);
}
*/
/*******************************************************************************
Read R1 from SD card
*******************************************************************************/
/*
uint8_t SD_readRes1()
{
uint8_t i = 0, res1;
// keep polling until actual data received
while((res1 = spi_exchange(0xFF)) == 0xFF)
{
i++;
// if no data received for 8 bytes, break
if(i > 8) break;
}
return res1;
}
*/
/*******************************************************************************
Read R2 from SD card
*******************************************************************************/
/*
void SD_readRes2(uint8_t *res)
{
// read response 1 in R2
res[0] = SD_readRes1();
// read final byte of response
res[1] = spi_exchange(0xFF);
}
*/
/*******************************************************************************
Read R3 from SD card
*******************************************************************************/
/*
void SD_readRes3(uint8_t *res)
{
// read response 1 in R3
res[0] = SD_readRes1();
// if error reading R1, return
if(res[0] > 1) return;
// read remaining bytes
SD_readBytes(res + 1, R3_BYTES);
}
*/
/*******************************************************************************
Read R7 from SD card
*******************************************************************************/
/*
void SD_readRes7(uint8_t *res)
{
// read response 1 in R7
res[0] = SD_readRes1();
// if error reading R1, return
if(res[0] > 1) return;
// read remaining bytes
SD_readBytes(res + 1, R7_BYTES);
}
*/
/*******************************************************************************
Read specified number of bytes from SD card
*******************************************************************************/
/*
void SD_readBytes(uint8_t *res, uint8_t n)
{
while(n--) *res++ = spi_exchange(0xFF);
}
*/
/*******************************************************************************
Command Idle State (CMD0)
*******************************************************************************/
uint8_t SD_goIdleState()
{
return res1_cmd(CMD0, CMD0_ARG, CMD0_CRC);
}
/*******************************************************************************
Send Interface Conditions (CMD8)
*******************************************************************************/
void SD_sendIfCond(uint8_t *res)
{
// assert chip select
spi_exchange(0xFF);
spi_select(0);
spi_exchange(0xFF);
// send CMD8
SD_command(CMD8, CMD8_ARG, CMD8_CRC);
// read response
SD_readRes7(res);
//SD_readBytes(res + 1, R7_BYTES);
// deassert chip select
spi_exchange(0xFF);
spi_deselect(0);
spi_exchange(0xFF);
}
/*******************************************************************************
Read Status
*******************************************************************************/
void SD_sendStatus(uint8_t *res)
{
// assert chip select
spi_exchange(0xFF);
spi_select(0);
spi_exchange(0xFF);
// send CMD13
SD_command(CMD13, CMD13_ARG, CMD13_CRC);
// read response
SD_readRes2(res);
// deassert chip select
spi_exchange(0xFF);
spi_deselect(0);
spi_exchange(0xFF);
}
/*******************************************************************************
Read single 512 byte block
token = 0xFE - Successful read
token = 0x0X - Data error
token = 0xFF - timeout
*******************************************************************************/
// uint8_t SD_readSingleBlock(uint32_t addr, uint8_t *buf, uint8_t *token)
// {
// uint8_t res1, read;
// uint16_t readAttempts;
// uint16_t i;
// // set token to none
// *token = 0xFF;
// // assert chip select
// spi_exchange(0xFF);
// spi_select(0);
// spi_exchange(0xFF);
// // send CMD17
// SD_command(CMD17, addr, CMD17_CRC);
// // read R1
// res1 = SD_readRes1();
// // if response received from card
// if(res1 != 0xFF)
// {
// // wait for a response token (timeout = 100ms)
// readAttempts = 0;
// while(++readAttempts != SD_MAX_READ_ATTEMPTS)
// if((read = spi_exchange(0xFF)) != 0xFF) break;
// cprintf("read attempts: %d\r\n", readAttempts);
// // if response token is 0xFE
// if(read == SD_START_TOKEN)
// {
// // read 512 byte block
// for(i = 0; i < SD_BLOCK_LEN; i++) *buf++ = spi_exchange(0xFF);
// // read 16-bit CRC
// spi_exchange(0xFF);
// spi_exchange(0xFF);
// }
// // set token to card response
// *token = read;
// }
// // deassert chip select
// spi_exchange(0xFF);
// spi_deselect(0);
// spi_exchange(0xFF);
// return res1;
// }
#define SD_MAX_WRITE_ATTEMPTS 3907
/*******************************************************************************
Write single 512 byte block
token = 0x00 - busy timeout
token = 0x05 - data accepted
token = 0xFF - response timeout
*******************************************************************************/
uint8_t SD_writeSingleBlock(uint32_t addr, uint8_t *buf, uint8_t *token)
{
uint16_t readAttempts;
uint8_t res1, read;
uint16_t i;
/*
// set token to none
*token = 0xFF;
// assert chip select
spi_exchange(0xFF);
spi_select(0);
spi_exchange(0xFF);
// send CMD24
SD_command(CMD24, addr, CMD24_CRC);
// read response
res1 = SD_readRes1();
// if no error
if(res1 == SD_READY)
{
// send start token
spi_exchange(SD_START_TOKEN);
// write buffer to card
for(i = 0; i < SD_BLOCK_LEN; i++) spi_exchange(buf[i]);
// wait for a response (timeout = 250ms)
readAttempts = 0;
while(++readAttempts != SD_MAX_WRITE_ATTEMPTS)
if((read = spi_exchange(0xFF)) != 0xFF) { *token = 0xFF; break; }
// if data accepted
if((read & 0x1F) == 0x05)
{
// set token to data accepted
*token = 0x05;
// wait for write to finish (timeout = 250ms)
readAttempts = 0;
while(spi_exchange(0xFF) == 0x00)
if(++readAttempts == SD_MAX_WRITE_ATTEMPTS) { *token = 0x00; break; }
}
}
// deassert chip select
spi_exchange(0xFF);
spi_deselect(0);
spi_exchange(0xFF);
*/
return res1;
}
/*******************************************************************************
Reads OCR from SD Card
*******************************************************************************/
void SD_readOCR(uint8_t *res)
{
uint8_t tmp;
// assert chip select
spi_exchange(0xFF);
spi_select(0);
tmp = spi_exchange(0xFF);
if(tmp != 0xFF) while(spi_exchange(0xFF) != 0xFF) ;
// send CMD58
SD_command(CMD58, CMD58_ARG, CMD58_CRC);
// read response
SD_readRes3(res);
// deassert chip select
spi_exchange(0xFF);
spi_deselect(0);
spi_exchange(0xFF);
}
/*******************************************************************************
Send application command (CMD55)
*******************************************************************************/
uint8_t SD_sendApp()
{
return res1_cmd(CMD55, CMD55_ARG, CMD55_CRC);;
}
/*******************************************************************************
Send operating condition (ACMD41)
*******************************************************************************/
uint8_t SD_sendOpCond()
{
return res1_cmd(ACMD41, ACMD41_ARG, ACMD41_CRC);
}

80
sw/kernel/devices/sd_card.h Normal file
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#ifndef _SD_CARD_H
#define _SD_CARD_H
#include <stdint.h>
// command definitions
#define CMD0 0
#define CMD0_ARG 0x00000000
#define CMD0_CRC 0x94
#define CMD8 8
#define CMD8_ARG 0x0000001AA
#define CMD8_CRC 0x86
#define CMD9 9
#define CMD9_ARG 0x00000000
#define CMD9_CRC 0x00
#define CMD10 9
#define CMD10_ARG 0x00000000
#define CMD10_CRC 0x00
#define CMD13 13
#define CMD13_ARG 0x00000000
#define CMD13_CRC 0x00
#define CMD17 17
#define CMD17_CRC 0x00
#define CMD24 24
#define CMD24_CRC 0x00
#define CMD55 55
#define CMD55_ARG 0x00000000
#define CMD55_CRC 0x00
#define CMD58 58
#define CMD58_ARG 0x00000000
#define CMD58_CRC 0x00
#define ACMD41 41
#define ACMD41_ARG 0x40000000
#define ACMD41_CRC 0x00
#define SD_IN_IDLE_STATE 0x01
#define SD_READY 0x00
#define SD_R1_NO_ERROR(X) X < 0x02
#define R3_BYTES 4
#define R7_BYTES 4
#define CMD0_MAX_ATTEMPTS 255
#define CMD55_MAX_ATTEMPTS 255
#define SD_ERROR 1
#define SD_SUCCESS 0
#define SD_MAX_READ_ATTEMPTS 1563
#define SD_READ_START_TOKEN 0xFE
#define SD_INIT_CYCLES 80
#define SD_START_TOKEN 0xFE
#define SD_ERROR_TOKEN 0x00
#define SD_DATA_ACCEPTED 0x05
#define SD_DATA_REJECTED_CRC 0x0B
#define SD_DATA_REJECTED_WRITE 0x0D
#define SD_BLOCK_LEN 512
// SD functions
uint8_t SD_init();
void SD_powerUpSeq();
void SD_command(uint8_t cmd, uint32_t arg, uint8_t crc);
uint8_t SD_readRes1();
void SD_readRes2(uint8_t *res);
void SD_readRes3(uint8_t *res);
void SD_readRes7(uint8_t *res);
void SD_readBytes(uint8_t *res, uint8_t n);
uint8_t SD_goIdleState();
void SD_sendIfCond(uint8_t *res);
void SD_sendStatus(uint8_t *res);
void SD_readOCR(uint8_t *res);
uint8_t SD_sendApp();
uint8_t SD_sendOpCond();
uint8_t SD_readSingleBlock(uint32_t addr, uint8_t *buf, uint8_t *error);
uint8_t SD_writeSingleBlock(uint32_t addr, uint8_t *buf, uint8_t *res);
uint8_t res1_cmd(uint8_t cmd, uint32_t arg, uint8_t crc);
#endif

303
sw/kernel/devices/sd_card_asm.s Normal file
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.export _SD_command
.export _SD_readRes1
.export _SD_readRes2
.export _SD_readRes3
.export _SD_readRes7
.export _SD_readBytes
.export _SD_powerUpSeq
.export _res1_cmd
.export _SD_readSingleBlock
.importzp sp, ptr1, ptr2, ptr3, ptr4, tmp1, tmp2, tmp3
.autoimport on
.MACPACK generic
; void SD_command(uint8_t cmd, uint32_t arg, uint8_t crc)
; The plan: push crc to stack, load arg into tmp1 through 4
.proc _SD_command: near
pha ; Push CRC to cpu stack
ldy #$04
lda (sp),y ; Load CMD
ora #$40 ; start bit
jsr _spi_exchange
dey
arg_loop: ; send ARG
lda (sp),y ; is this sending only 3?
jsr _spi_exchange
dey
bpl arg_loop
pla ; Pull CRC from stack
ora #$01 ; stop bit
jsr _spi_exchange
jsr incsp5 ; pop all off stack
rts
.endproc
; uint8_t SD_readRes1 (void)
.proc _SD_readRes1: near
; Try to read/write up to 8 times, then return value
ldx #$08
tryread:
lda #$ff
jsr _spi_exchange
cmp #$ff
bne end
dex
bne tryread
end: ; x will be 0 here anyway
rts
.endproc
; void SD_readRes2(uint8_t *res)
.proc _SD_readRes2: near
sta ptr1 ; store res in ptr1
stx ptr1 + 1
jsr _SD_readRes1 ; get first response 1
sta (ptr1)
lda #$ff
jsr _spi_exchange ; get final byte of response
ldy #$01
sta (ptr1),y
jsr incsp2
rts
.endproc
; void SD_readBytes(uint8_t *res, uint8_t n)
.proc _SD_readBytes: near
tax
jsr popptr1 ; store res in ptr1
read:
lda #$ff ; read data first
jsr _spi_exchange
sta (ptr1)
inc ptr1 ; then increment res
bne @L1
inc ptr1 + 1
@L1: dex ; then decrement x
bne read ; and if x is zero we are done
rts
.endproc
; void SD_readRes7(uint8_t *res)
_SD_readRes7:
; void SD_readRes3(uint8_t *res)
.proc _SD_readRes3: near
sta ptr1 ; store res in ptr1
stx ptr1 + 1
jsr _SD_readRes1 ; read respopnse 1 in R3
cmp #$02 ; if error reading R1, return
bge @L1
inc ptr1 ; read remaining bytes
bne @L2
inc ptr1
@L2: lda ptr1 ; push low byte
ldx ptr1 + 1
jsr pushax
lda #$04 ; R3_BYTES
jsr _SD_readBytes
@L1: rts
.endproc
; uint8_t res1_cmd(uint8_t cmd, uint32_t arg, uint8_t crc)
.proc _res1_cmd: near
pha ; push crc to processor stack
lda #$ff
jsr _spi_exchange
lda #$00 ; this gets ignored anyway
jsr _spi_select
lda #$ff
jsr _spi_exchange
pla
jsr _SD_command ; rely on command to teardown stack
jsr _SD_readRes1
tay ; spi doesn't touch y
lda #$ff
jsr _spi_exchange
lda #$00 ; this gets ignored anyway
jsr _spi_deselect
lda #$ff
jsr _spi_exchange
tya
ldx #$00 ; Promote to integer
rts
.endproc
; void SD_powerUpSeq(void)
.proc _SD_powerUpSeq: near
lda #$00
jsr _spi_deselect
jsr _sd_delay
lda #$ff
jsr _spi_exchange
lda #$00
jsr _spi_deselect
ldx #$50 ; SD_INIT_CYCLES
@L1: lda #$ff
jsr _spi_exchange
dex
bne @L1
rts
.endproc
; 1ms delay approx. saves no registers
.proc _sd_delay: near
ldx #$01 ; delay loop: A*X*10 + 4
@L1: lda #$c8 ; 1ms at 2MHz
@L2: dec ; 2
bne @L2 ; 3
dex ; 2
bne @L1 ; 3
rts
.endproc
; ;uint8_t SD_readSingleBlock(uint32_t addr, uint8_t *buf, uint8_t *token)
.proc _SD_readSingleBlock: near
; token address in a/x
; buf address next on stack
; sd address above that
; ptr2 = *token
sta ptr2
stx ptr2 + 1
lda #$ff
sta (ptr2)
; ptr1 = *buf
jsr popptr1
; 4 bytes on stack are addr
; Move addr down on the stack
lda sp
sta ptr3
lda sp + 1
sta ptr3 + 1
; find a way to do this in a loop?
jsr decsp1
ldy #$0
lda (ptr3),y
sta (sp),y
iny
lda (ptr3),y
sta (sp),y
iny
lda (ptr3),y
sta (sp),y
iny
lda (ptr3),y
sta (sp),y
lda #$ff
jsr _spi_exchange
lda #$00 ; this gets ignored anyway
jsr _spi_select
lda #$ff
jsr _spi_exchange
; push cmd17
lda #$11
ldy #$4
sta (sp),y
; crc, 0
lda #$00
jsr _SD_command ; rely on command to teardown stack
jsr _SD_readRes1
cmp #$ff ; if 0xFF then you failed
beq end
sta tmp3 ; tmp3 = read
; y = read_attempts
ldy #$0
resp_loop:
lda #$ff
jsr _spi_exchange
sta tmp2 ; tmp2 = read
lda tmp2
cmp #$ff
bne got_resp
iny
bne resp_loop
bra after_read
got_resp:
ldx #$2
ldy #$00
load_loop:
lda #$ff
jsr _spi_exchange
sta (ptr1)
inc ptr1
bne @2
inc ptr1 + 1
@2: dey
bne load_loop
ldy #$00
dex
bne load_loop
lda #$ff
jsr _spi_exchange
lda #$ff
jsr _spi_exchange
after_read:
lda tmp2
sta (ptr2)
lda tmp3
end:
pha
lda #$ff
jsr _spi_exchange
lda #$00 ; this gets ignored anyway
jsr _spi_deselect
lda #$ff
jsr _spi_exchange
pla
rts
.endproc

26
sw/kernel/devices/sd_print.c Normal file
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#include <conio.h>
#include "sd_print.h"
#include "sd_card.h"
void SD_printBuf(uint8_t *buf)
{
uint8_t colCount = 0;
uint16_t i;
for(i = 0; i < SD_BLOCK_LEN; i++)
{
cprintf("%2x", *buf++);
if(colCount == 31)
{
cputs("\r\n");
colCount = 0;
}
else
{
cputc(' ');
colCount++;
}
}
cputs("\r\n");
}

61
sw/kernel/devices/sd_print.h Normal file
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#ifndef SD_PRINT_H
#define SD_PRINT_H
#include <stdint.h>
/* R1 MACROS */
#define PARAM_ERROR(X) X & 0b01000000
#define ADDR_ERROR(X) X & 0b00100000
#define ERASE_SEQ_ERROR(X) X & 0b00010000
#define CRC_ERROR(X) X & 0b00001000
#define ILLEGAL_CMD(X) X & 0b00000100
#define ERASE_RESET(X) X & 0b00000010
#define IN_IDLE(X) X & 0b00000001
/* R2 MACROS */
#define OUT_OF_RANGE(X) X & 0b10000000
#define ERASE_PARAM(X) X & 0b01000000
#define WP_VIOLATION(X) X & 0b00100000
#define CARD_ECC_FAILED(X) X & 0b00010000
#define CC_ERROR(X) X & 0b00001000
#define ERROR(X) X & 0b00000100
#define WP_ERASE_SKIP(X) X & 0b00000010
#define CARD_LOCKED(X) X & 0b00000001
/* R3 MACROS */
#define POWER_UP_STATUS(X) X & 0x40
#define CCS_VAL(X) X & 0x40
#define VDD_2728(X) X & 0b10000000
#define VDD_2829(X) X & 0b00000001
#define VDD_2930(X) X & 0b00000010
#define VDD_3031(X) X & 0b00000100
#define VDD_3132(X) X & 0b00001000
#define VDD_3233(X) X & 0b00010000
#define VDD_3334(X) X & 0b00100000
#define VDD_3435(X) X & 0b01000000
#define VDD_3536(X) X & 0b10000000
/* R7 MACROS */
#define CMD_VER(X) ((X >> 4) & 0xF0)
#define VOL_ACC(X) (X & 0x1F)
#define VOLTAGE_ACC_27_33 0b00000001
#define VOLTAGE_ACC_LOW 0b00000010
#define VOLTAGE_ACC_RES1 0b00000100
#define VOLTAGE_ACC_RES2 0b00001000
/* DATA ERROR TOKEN */
#define SD_TOKEN_OOR(X) X & 0b00001000
#define SD_TOKEN_CECC(X) X & 0b00000100
#define SD_TOKEN_CC(X) X & 0b00000010
#define SD_TOKEN_ERROR(X) X & 0b00000001
void SD_printR1(uint8_t res);
void SD_printR2(uint8_t *res);
void SD_printR3(uint8_t *res);
void SD_printR7(uint8_t *res);
void SD_printBuf(uint8_t *buf);
void SD_printDataErrToken(uint8_t token);
#endif

12
sw/kernel/devices/spi.h Normal file
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@@ -0,0 +1,12 @@
#ifndef _SPI_H
#define _SPI_H
#include <stdint.h>
void spi_select(uint8_t id);
void spi_deselect(uint8_t id);
uint8_t spi_read();
void spi_write(uint8_t data);
uint8_t spi_exchange(uint8_t data);
#endif

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sw/kernel/devices/spi.s Normal file
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.include "io.inc65"
.importzp zp, sreg
.export _spi_select, _spi_deselect
.export _spi_read, _spi_write, _spi_exchange
.autoimport on
.code
; void spi_select(uint8_t id)
; Select a (the) slave by pulling its CS line down
; TODO allow active high or active low CS
; TODO allow more than one slave
_spi_select:
lda #$1 ; Ignore whatever id is, 1 is the only option
sta SPI_CTRL
rts
; void spi_deslect(uint8_t id)
; Deslect a slave by pulling its CS line up
; TODO allow active high or active low CS
_spi_deselect:
stz SPI_CTRL
rts
; uint8_t spi_read()
_spi_read:
lda #$0
; void spi_write(uint8_t data)
_spi_write:
; uint8_t spi_exchange(uint8_t data)
_spi_exchange:
sta SPI_OUTPUT
@1: lda SPI_CTRL
bmi @1
lda SPI_INPUT
rts

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sw/kernel/irq.c Normal file
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#include <stdint.h>
#include <conio.h>
#include "devices/interrupt.h"
#include "devices/uart.h"
void handle_irq() {
}