From 8f3a1a596832d3d7f520d63824f3e03e003c0e0d Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Sun, 23 Jul 2023 18:43:39 -0700
Subject: [PATCH] res1_cmd assembly rewrite

---
 sw/bootloader/devices/sd_card.c     |  2 ++
 sw/bootloader/devices/sd_card.h     |  2 ++
 sw/bootloader/devices/sd_card_asm.s | 34 ++++++++++++++++++++++++++++-
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/sw/bootloader/devices/sd_card.c b/sw/bootloader/devices/sd_card.c
index 1c72a0a..55b4341 100644
--- a/sw/bootloader/devices/sd_card.c
+++ b/sw/bootloader/devices/sd_card.c
@@ -67,6 +67,7 @@ uint8_t SD_init()
     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)
 {
@@ -89,6 +90,7 @@ uint8_t res1_cmd(uint8_t cmd, uint32_t arg, uint8_t crc)
 
     return res1;
 }
+*/
 
 /*******************************************************************************
  Run power up sequence
diff --git a/sw/bootloader/devices/sd_card.h b/sw/bootloader/devices/sd_card.h
index 6488e8b..3e9304d 100644
--- a/sw/bootloader/devices/sd_card.h
+++ b/sw/bootloader/devices/sd_card.h
@@ -75,4 +75,6 @@ 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
\ No newline at end of file
diff --git a/sw/bootloader/devices/sd_card_asm.s b/sw/bootloader/devices/sd_card_asm.s
index 99aa055..f377964 100644
--- a/sw/bootloader/devices/sd_card_asm.s
+++ b/sw/bootloader/devices/sd_card_asm.s
@@ -3,6 +3,7 @@
 .export _SD_readRes2
 .export _SD_readRes3
 .export _SD_readBytes
+.export _res1_cmd
 
 .importzp sp, ptr1
 
@@ -52,7 +53,7 @@ tryread:
         dex
         bne     tryread
 
-end:
+end:                            ; x will be 0 here anyway
         rts
 
 .endproc
@@ -120,4 +121,35 @@ read:
 
 @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
\ No newline at end of file