initial experiments

1 files changed, 749 insertions, 0 deletions

diff --git a/usbdrv/usbdrvasm128.inc b/usbdrv/usbdrvasm128.inc
new file mode 100644
index 0000000..8f67bcc
--- /dev/null
+++ b/usbdrv/usbdrvasm128.inc
@@ -0,0 +1,749 @@
+/* Name: usbdrvasm128.inc
+ * Project: V-USB, virtual USB port for Atmel's(r) AVR(r) microcontrollers
+ * Author: Christian Starkjohann
+ * Creation Date: 2008-10-11
+ * Tabsize: 4
+ * Copyright: (c) 2008 by OBJECTIVE DEVELOPMENT Software GmbH
+ * License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt)
+ */
+
+/* Do not link this file! Link usbdrvasm.S instead, which includes the
+ * appropriate implementation!
+ */
+
+/*
+General Description:
+This file is the 12.8 MHz version of the USB driver. It is intended for use
+with the internal RC oscillator. Although 12.8 MHz is outside the guaranteed
+calibration range of the oscillator, almost all AVRs can reach this frequency.
+This version contains a phase locked loop in the receiver routine to cope with
+slight clock rate deviations of up to +/- 1%.
+
+See usbdrv.h for a description of the entire driver.
+
+LIMITATIONS
+===========
+Although it may seem very handy to save the crystal and use the internal
+RC oscillator of the CPU, this method (and this module) has some serious
+limitations:
+(1) The guaranteed calibration range of the oscillator is only 8.1 MHz.
+They typical range is 14.5 MHz and most AVRs can actually reach this rate.
+(2) Writing EEPROM and Flash may be unreliable (short data lifetime) since
+the write procedure is timed from the RC oscillator.
+(3) End Of Packet detection (SE0) should be in bit 1, bit it is only checked
+if bits 0 and 1 both read as 0 on D- and D+ read as 0 in the middle. This may
+cause problems with old hubs which delay SE0 by up to one cycle.
+(4) Code size is much larger than that of the other modules.
+
+Since almost all of this code is timing critical, don't change unless you
+really know what you are doing! Many parts require not only a maximum number
+of CPU cycles, but even an exact number of cycles!
+
+Implementation notes:
+======================
+min frequency: 67 cycles for 8 bit -> 12.5625 MHz
+max frequency: 69.286 cycles for 8 bit -> 12.99 MHz
+nominal frequency: 12.77 MHz ( = sqrt(min * max))
+
+sampling positions: (next even number in range [+/- 0.5])
+cycle index range: 0 ... 66
+bits:
+.5, 8.875, 17.25, 25.625, 34, 42.375, 50.75, 59.125
+[0/1], [9], [17], [25/+26], [34], [+42/43], [51], [59]
+
+bit number:     0   1   2   3   4   5   6   7
+spare cycles    1   2   1   2   1   1   1   0
+
+operations to perform:      duration cycle
+                            ----------------
+    eor     fix, shift          1 -> 00
+    andi    phase, USBMASK      1 -> 08
+    breq    se0                 1 -> 16 (moved to 11)
+    st      y+, data            2 -> 24, 25
+    mov     data, fix           1 -> 33
+    ser     data                1 -> 41
+    subi    cnt, 1              1 -> 49
+    brcs    overflow            1 -> 50
+
+layout of samples and operations:
+[##] = sample bit
+<##> = sample phase
+*##* = operation
+
+0:  *00* [01]  02   03   04  <05>  06   07
+1:  *08* [09]  10   11   12  <13>  14   15  *16*
+2:  [17]  18   19   20  <21>  22   23
+3:  *24* *25* [26]  27   28   29  <30>  31   32
+4:  *33* [34]  35   36   37  <38>  39   40
+5:  *41* [42]  43   44   45  <46>  47   48
+6:  *49* *50* [51]  52   53   54  <55>  56   57   58
+7:  [59]  60   61   62  <63>  64   65   66
+*****************************************************************************/
+
+/* we prefer positive expressions (do if condition) instead of negative
+ * (skip if condition), therefore use defines for skip instructions:
+ */
+#define ifioclr sbis
+#define ifioset sbic
+#define ifrclr  sbrs
+#define ifrset  sbrc
+
+/* The registers "fix" and "data" swap their meaning during the loop. Use
+ * defines to keep their name constant.
+ */
+#define fix     x2
+#define data    x1
+#undef phase        /* phase has a default definition to x4 */
+#define phase   x3
+
+
+USB_INTR_VECTOR:
+;order of registers pushed: YL, SREG [sofError], YH, shift, x1, x2, x3, cnt, r0
+    push    YL              ;2 push only what is necessary to sync with edge ASAP
+    in      YL, SREG        ;1
+    push    YL              ;2
+;----------------------------------------------------------------------------
+; Synchronize with sync pattern:
+;----------------------------------------------------------------------------
+;sync byte (D-) pattern LSb to MSb: 01010100 [1 = idle = J, 0 = K]
+;sync up with J to K edge during sync pattern -- use fastest possible loops
+;The first part waits at most 1 bit long since we must be in sync pattern.
+;YL is guarenteed to be < 0x80 because I flag is clear. When we jump to
+;waitForJ, ensure that this prerequisite is met.
+waitForJ:
+    inc     YL
+    sbis    USBIN, USBMINUS
+    brne    waitForJ        ; just make sure we have ANY timeout
+waitForK:
+;The following code results in a sampling window of 1/4 bit which meets the spec.
+    sbis    USBIN, USBMINUS
+    rjmp    foundK
+    sbis    USBIN, USBMINUS
+    rjmp    foundK
+    sbis    USBIN, USBMINUS
+    rjmp    foundK
+    sbis    USBIN, USBMINUS
+    rjmp    foundK
+    sbis    USBIN, USBMINUS ;[0]
+    rjmp    foundK          ;[1]
+#if USB_COUNT_SOF
+    lds     YL, usbSofCount
+    inc     YL
+    sts     usbSofCount, YL
+#endif  /* USB_COUNT_SOF */
+#ifdef USB_SOF_HOOK
+    USB_SOF_HOOK
+#endif
+    rjmp    sofError
+
+foundK:
+;{3, 5} after falling D- edge, average delay: 4 cycles [we want 4 for center sampling]
+;we have 1 bit time for setup purposes, then sample again. Numbers in brackets
+;are cycles from center of first sync (double K) bit after the instruction
+    push    YH                  ;[2]
+    lds     YL, usbInputBufOffset;[4]
+    clr     YH                  ;[6]
+    subi    YL, lo8(-(usbRxBuf));[7]
+    sbci    YH, hi8(-(usbRxBuf));[8]
+
+    sbis    USBIN, USBMINUS     ;[9] we want two bits K [we want to sample at 8 + 4 - 1.5 = 10.5]
+    rjmp    haveTwoBitsK        ;[10]
+    pop     YH                  ;[11] undo the push from before
+    rjmp    waitForK            ;[13] this was not the end of sync, retry
+haveTwoBitsK:
+;----------------------------------------------------------------------------
+; push more registers and initialize values while we sample the first bits:
+;----------------------------------------------------------------------------
+#define fix     x2
+#define data    x1
+
+    push    shift               ;[12]
+    push    x1                  ;[14]
+    push    x2                  ;[16]
+    ldi     shift, 0x80         ;[18] prevent bit-unstuffing but init low bits to 0
+    ifioset USBIN, USBMINUS     ;[19] [01] <--- bit 0 [10.5 + 8 = 18.5]
+    ori     shift, 1<<0         ;[02]
+    push    x3                  ;[03]
+    push    cnt                 ;[05]
+    push    r0                  ;[07]
+    ifioset USBIN, USBMINUS     ;[09] <--- bit 1
+    ori     shift, 1<<1         ;[10]
+    ser     fix                 ;[11]
+    ldi     cnt, USB_BUFSIZE    ;[12]
+    mov     data, shift         ;[13]
+    lsl     shift               ;[14]
+    nop2                        ;[15]
+    ifioset USBIN, USBMINUS     ;[17] <--- bit 2
+    ori     data, 3<<2          ;[18] store in bit 2 AND bit 3
+    eor     shift, data         ;[19] do nrzi decoding
+    andi    data, 1<<3          ;[20]
+    in      phase, USBIN        ;[21] <- phase
+    brne    jumpToEntryAfterSet ;[22] if USBMINS at bit 3 was 1
+    nop                         ;[23]
+    rjmp    entryAfterClr       ;[24]
+jumpToEntryAfterSet:
+    rjmp    entryAfterSet       ;[24]
+
+;----------------------------------------------------------------------------
+; Receiver loop (numbers in brackets are cycles within byte after instr)
+;----------------------------------------------------------------------------
+#undef  fix
+#define  fix    x1
+#undef  data
+#define data    x2
+
+bit7IsSet:
+    ifrclr  phase, USBMINUS     ;[62] check phase only if D- changed
+    lpm                         ;[63]
+    in      phase, USBIN        ;[64] <- phase (one cycle too late)
+    ori     shift, 1 << 7       ;[65]
+    nop                         ;[66]
+;;;;rjmp    bit0AfterSet        ; -> [00] == [67] moved block up to save jump
+bit0AfterSet:
+    eor     fix, shift          ;[00]
+#undef  fix
+#define fix     x2
+#undef  data
+#define data    x1  /* we now have result in data, fix is reset to 0xff */
+    ifioclr USBIN, USBMINUS     ;[01] <--- sample 0
+    rjmp    bit0IsClr           ;[02]
+    andi    shift, ~(7 << 0)    ;[03]
+    breq    unstuff0s           ;[04]
+    in      phase, USBIN        ;[05] <- phase
+    rjmp    bit1AfterSet        ;[06]
+unstuff0s:
+    in      phase, USBIN        ;[06] <- phase (one cycle too late)
+    andi    fix, ~(1 << 0)      ;[07]
+    ifioclr USBIN, USBMINUS     ;[00]
+    ifioset USBIN, USBPLUS      ;[01]
+    rjmp    bit0IsClr           ;[02] executed if first expr false or second true
+se0AndStore:                    ; executed only if both bits 0
+    st      y+, x1              ;[15/17] cycles after start of byte
+    rjmp    se0                 ;[17/19]
+
+bit0IsClr:
+    ifrset  phase, USBMINUS     ;[04] check phase only if D- changed
+    lpm                         ;[05]
+    in      phase, USBIN        ;[06] <- phase (one cycle too late)
+    ori     shift, 1 << 0       ;[07]
+bit1AfterClr:
+    andi    phase, USBMASK      ;[08]
+    ifioset USBIN, USBMINUS     ;[09] <--- sample 1
+    rjmp    bit1IsSet           ;[10]
+    breq    se0AndStore         ;[11] if D- was 0 in bits 0 AND 1 and D+ was 0 in between, we have SE0
+    andi    shift, ~(7 << 1)    ;[12]
+    in      phase, USBIN        ;[13] <- phase
+    breq    unstuff1c           ;[14]
+    rjmp    bit2AfterClr        ;[15]
+unstuff1c:
+    andi    fix, ~(1 << 1)      ;[16]
+    nop2                        ;[08]
+    nop2                        ;[10]
+bit1IsSet:
+    ifrclr  phase, USBMINUS     ;[12] check phase only if D- changed
+    lpm                         ;[13]
+    in      phase, USBIN        ;[14] <- phase (one cycle too late)
+    ori     shift, 1 << 1       ;[15]
+    nop                         ;[16]
+bit2AfterSet:
+    ifioclr USBIN, USBMINUS     ;[17] <--- sample 2
+    rjmp    bit2IsClr           ;[18]
+    andi    shift, ~(7 << 2)    ;[19]
+    breq    unstuff2s           ;[20]
+    in      phase, USBIN        ;[21] <- phase
+    rjmp    bit3AfterSet        ;[22]
+unstuff2s:
+    in      phase, USBIN        ;[22] <- phase (one cycle too late)
+    andi    fix, ~(1 << 2)      ;[23]
+    nop2                        ;[16]
+    nop2                        ;[18]
+bit2IsClr:
+    ifrset  phase, USBMINUS     ;[20] check phase only if D- changed
+    lpm                         ;[21]
+    in      phase, USBIN        ;[22] <- phase (one cycle too late)
+    ori     shift, 1 << 2       ;[23]
+bit3AfterClr:
+    st      y+, data            ;[24]
+entryAfterClr:
+    ifioset USBIN, USBMINUS     ;[26] <--- sample 3
+    rjmp    bit3IsSet           ;[27]
+    andi    shift, ~(7 << 3)    ;[28]
+    breq    unstuff3c           ;[29]
+    in      phase, USBIN        ;[30] <- phase
+    rjmp    bit4AfterClr        ;[31]
+unstuff3c:
+    in      phase, USBIN        ;[31] <- phase (one cycle too late)
+    andi    fix, ~(1 << 3)      ;[32]
+    nop2                        ;[25]
+    nop2                        ;[27]
+bit3IsSet:
+    ifrclr  phase, USBMINUS     ;[29] check phase only if D- changed
+    lpm                         ;[30]
+    in      phase, USBIN        ;[31] <- phase (one cycle too late)
+    ori     shift, 1 << 3       ;[32]
+bit4AfterSet:
+    mov     data, fix           ;[33] undo this move by swapping defines
+#undef  fix
+#define fix     x1
+#undef  data
+#define data    x2
+    ifioclr USBIN, USBMINUS     ;[34] <--- sample 4
+    rjmp    bit4IsClr           ;[35]
+    andi    shift, ~(7 << 4)    ;[36]
+    breq    unstuff4s           ;[37]
+    in      phase, USBIN        ;[38] <- phase
+    rjmp    bit5AfterSet        ;[39]
+unstuff4s:
+    in      phase, USBIN        ;[39] <- phase (one cycle too late)
+    andi    fix, ~(1 << 4)      ;[40]
+    nop2                        ;[33]
+    nop2                        ;[35]
+bit4IsClr:
+    ifrset  phase, USBMINUS     ;[37] check phase only if D- changed
+    lpm                         ;[38]
+    in      phase, USBIN        ;[39] <- phase (one cycle too late)
+    ori     shift, 1 << 4       ;[40]
+bit5AfterClr:
+    ser     data                ;[41]
+    ifioset USBIN, USBMINUS     ;[42] <--- sample 5
+    rjmp    bit5IsSet           ;[43]
+    andi    shift, ~(7 << 5)    ;[44]
+    breq    unstuff5c           ;[45]
+    in      phase, USBIN        ;[46] <- phase
+    rjmp    bit6AfterClr        ;[47]
+unstuff5c:
+    in      phase, USBIN        ;[47] <- phase (one cycle too late)
+    andi    fix, ~(1 << 5)      ;[48]
+    nop2                        ;[41]
+    nop2                        ;[43]
+bit5IsSet:
+    ifrclr  phase, USBMINUS     ;[45] check phase only if D- changed
+    lpm                         ;[46]
+    in      phase, USBIN        ;[47] <- phase (one cycle too late)
+    ori     shift, 1 << 5       ;[48]
+bit6AfterSet:
+    subi    cnt, 1              ;[49]
+    brcs    jumpToOverflow      ;[50]
+    ifioclr USBIN, USBMINUS     ;[51] <--- sample 6
+    rjmp    bit6IsClr           ;[52]
+    andi    shift, ~(3 << 6)    ;[53]
+    cpi     shift, 2            ;[54]
+    in      phase, USBIN        ;[55] <- phase
+    brlt    unstuff6s           ;[56]
+    rjmp    bit7AfterSet        ;[57]
+
+jumpToOverflow:
+    rjmp    overflow
+
+unstuff6s:
+    andi    fix, ~(1 << 6)      ;[50]
+    lpm                         ;[51]
+bit6IsClr:
+    ifrset  phase, USBMINUS     ;[54] check phase only if D- changed
+    lpm                         ;[55]
+    in      phase, USBIN        ;[56] <- phase (one cycle too late)
+    ori     shift, 1 << 6       ;[57]
+    nop                         ;[58]
+bit7AfterClr:
+    ifioset USBIN, USBMINUS     ;[59] <--- sample 7
+    rjmp    bit7IsSet           ;[60]
+    andi    shift, ~(1 << 7)    ;[61]
+    cpi     shift, 4            ;[62]
+    in      phase, USBIN        ;[63] <- phase
+    brlt    unstuff7c           ;[64]
+    rjmp    bit0AfterClr        ;[65] -> [00] == [67]
+unstuff7c:
+    andi    fix, ~(1 << 7)      ;[58]
+    nop                         ;[59]
+    rjmp    bit7IsSet           ;[60]
+
+bit7IsClr:
+    ifrset  phase, USBMINUS     ;[62] check phase only if D- changed
+    lpm                         ;[63]
+    in      phase, USBIN        ;[64] <- phase (one cycle too late)
+    ori     shift, 1 << 7       ;[65]
+    nop                         ;[66]
+;;;;rjmp    bit0AfterClr        ; -> [00] == [67] moved block up to save jump
+bit0AfterClr:
+    eor     fix, shift          ;[00]
+#undef  fix
+#define fix     x2
+#undef  data
+#define data    x1  /* we now have result in data, fix is reset to 0xff */
+    ifioset USBIN, USBMINUS     ;[01] <--- sample 0
+    rjmp    bit0IsSet           ;[02]
+    andi    shift, ~(7 << 0)    ;[03]
+    breq    unstuff0c           ;[04]
+    in      phase, USBIN        ;[05] <- phase
+    rjmp    bit1AfterClr        ;[06]
+unstuff0c:
+    in      phase, USBIN        ;[06] <- phase (one cycle too late)
+    andi    fix, ~(1 << 0)      ;[07]
+    ifioclr USBIN, USBMINUS     ;[00]
+    ifioset USBIN, USBPLUS      ;[01]
+    rjmp    bit0IsSet           ;[02] executed if first expr false or second true
+    rjmp    se0AndStore         ;[03] executed only if both bits 0
+bit0IsSet:
+    ifrclr  phase, USBMINUS     ;[04] check phase only if D- changed
+    lpm                         ;[05]
+    in      phase, USBIN        ;[06] <- phase (one cycle too late)
+    ori     shift, 1 << 0       ;[07]
+bit1AfterSet:
+    andi    shift, ~(7 << 1)    ;[08] compensated by "ori shift, 1<<1" if bit1IsClr
+    ifioclr USBIN, USBMINUS     ;[09] <--- sample 1
+    rjmp    bit1IsClr           ;[10]
+    breq    unstuff1s           ;[11]
+    nop2                        ;[12] do not check for SE0 if bit 0 was 1
+    in      phase, USBIN        ;[14] <- phase (one cycle too late)
+    rjmp    bit2AfterSet        ;[15]
+unstuff1s:
+    in      phase, USBIN        ;[13] <- phase
+    andi    fix, ~(1 << 1)      ;[14]
+    lpm                         ;[07]
+    nop2                        ;[10]
+bit1IsClr:
+    ifrset  phase, USBMINUS     ;[12] check phase only if D- changed
+    lpm                         ;[13]
+    in      phase, USBIN        ;[14] <- phase (one cycle too late)
+    ori     shift, 1 << 1       ;[15]
+    nop                         ;[16]
+bit2AfterClr:
+    ifioset USBIN, USBMINUS     ;[17] <--- sample 2
+    rjmp    bit2IsSet           ;[18]
+    andi    shift, ~(7 << 2)    ;[19]
+    breq    unstuff2c           ;[20]
+    in      phase, USBIN        ;[21] <- phase
+    rjmp    bit3AfterClr        ;[22]
+unstuff2c:
+    in      phase, USBIN        ;[22] <- phase (one cycle too late)
+    andi    fix, ~(1 << 2)      ;[23]
+    nop2                        ;[16]
+    nop2                        ;[18]
+bit2IsSet:
+    ifrclr  phase, USBMINUS     ;[20] check phase only if D- changed
+    lpm                         ;[21]
+    in      phase, USBIN        ;[22] <- phase (one cycle too late)
+    ori     shift, 1 << 2       ;[23]
+bit3AfterSet:
+    st      y+, data            ;[24]
+entryAfterSet:
+    ifioclr USBIN, USBMINUS     ;[26] <--- sample 3
+    rjmp    bit3IsClr           ;[27]
+    andi    shift, ~(7 << 3)    ;[28]
+    breq    unstuff3s           ;[29]
+    in      phase, USBIN        ;[30] <- phase
+    rjmp    bit4AfterSet        ;[31]
+unstuff3s:
+    in      phase, USBIN        ;[31] <- phase (one cycle too late)
+    andi    fix, ~(1 << 3)      ;[32]
+    nop2                        ;[25]
+    nop2                        ;[27]
+bit3IsClr:
+    ifrset  phase, USBMINUS     ;[29] check phase only if D- changed
+    lpm                         ;[30]
+    in      phase, USBIN        ;[31] <- phase (one cycle too late)
+    ori     shift, 1 << 3       ;[32]
+bit4AfterClr:
+    mov     data, fix           ;[33] undo this move by swapping defines
+#undef  fix
+#define fix     x1
+#undef  data
+#define data    x2
+    ifioset USBIN, USBMINUS     ;[34] <--- sample 4
+    rjmp    bit4IsSet           ;[35]
+    andi    shift, ~(7 << 4)    ;[36]
+    breq    unstuff4c           ;[37]
+    in      phase, USBIN        ;[38] <- phase
+    rjmp    bit5AfterClr        ;[39]
+unstuff4c:
+    in      phase, USBIN        ;[39] <- phase (one cycle too late)
+    andi    fix, ~(1 << 4)      ;[40]
+    nop2                        ;[33]
+    nop2                        ;[35]
+bit4IsSet:
+    ifrclr  phase, USBMINUS     ;[37] check phase only if D- changed
+    lpm                         ;[38]
+    in      phase, USBIN        ;[39] <- phase (one cycle too late)
+    ori     shift, 1 << 4       ;[40]
+bit5AfterSet:
+    ser     data                ;[41]
+    ifioclr USBIN, USBMINUS     ;[42] <--- sample 5
+    rjmp    bit5IsClr           ;[43]
+    andi    shift, ~(7 << 5)    ;[44]
+    breq    unstuff5s           ;[45]
+    in      phase, USBIN        ;[46] <- phase
+    rjmp    bit6AfterSet        ;[47]
+unstuff5s:
+    in      phase, USBIN        ;[47] <- phase (one cycle too late)
+    andi    fix, ~(1 << 5)      ;[48]
+    nop2                        ;[41]
+    nop2                        ;[43]
+bit5IsClr:
+    ifrset  phase, USBMINUS     ;[45] check phase only if D- changed
+    lpm                         ;[46]
+    in      phase, USBIN        ;[47] <- phase (one cycle too late)
+    ori     shift, 1 << 5       ;[48]
+bit6AfterClr:
+    subi    cnt, 1              ;[49]
+    brcs    overflow            ;[50]
+    ifioset USBIN, USBMINUS     ;[51] <--- sample 6
+    rjmp    bit6IsSet           ;[52]
+    andi    shift, ~(3 << 6)    ;[53]
+    cpi     shift, 2            ;[54]
+    in      phase, USBIN        ;[55] <- phase
+    brlt    unstuff6c           ;[56]
+    rjmp    bit7AfterClr        ;[57]
+unstuff6c:
+    andi    fix, ~(1 << 6)      ;[50]
+    lpm                         ;[51]
+bit6IsSet:
+    ifrclr  phase, USBMINUS     ;[54] check phase only if D- changed
+    lpm                         ;[55]
+    in      phase, USBIN        ;[56] <- phase (one cycle too late)
+    ori     shift, 1 << 6       ;[57]
+bit7AfterSet:
+    ifioclr USBIN, USBMINUS     ;[59] <--- sample 7
+    rjmp    bit7IsClr           ;[60]
+    andi    shift, ~(1 << 7)    ;[61]
+    cpi     shift, 4            ;[62]
+    in      phase, USBIN        ;[63] <- phase
+    brlt    unstuff7s           ;[64]
+    rjmp    bit0AfterSet        ;[65] -> [00] == [67]
+unstuff7s:
+    andi    fix, ~(1 << 7)      ;[58]
+    nop                         ;[59]
+    rjmp    bit7IsClr           ;[60]
+
+macro POP_STANDARD ; 14 cycles
+    pop     r0
+    pop     cnt
+    pop     x3
+    pop     x2
+    pop     x1
+    pop     shift
+    pop     YH
+    endm
+macro POP_RETI     ; 5 cycles
+    pop     YL
+    out     SREG, YL
+    pop     YL
+    endm
+
+#include "asmcommon.inc"
+
+;----------------------------------------------------------------------------
+; Transmitting data
+;----------------------------------------------------------------------------
+
+txByteLoop:
+txBitloop:
+stuffN1Delay:                   ;     [03]
+    ror     shift               ;[-5] [11] [63]
+    brcc    doExorN1            ;[-4]      [64]
+    subi    x3, 1               ;[-3]
+    brne    commonN1            ;[-2]
+    lsl     shift               ;[-1] compensate ror after rjmp stuffDelay
+    nop                         ;[00] stuffing consists of just waiting 8 cycles
+    rjmp    stuffN1Delay        ;[01] after ror, C bit is reliably clear
+
+sendNakAndReti:
+    ldi     cnt, USBPID_NAK ;[-19]
+    rjmp    sendCntAndReti  ;[-18]
+sendAckAndReti:
+    ldi     cnt, USBPID_ACK ;[-17]
+sendCntAndReti:
+    mov     r0, cnt         ;[-16]
+    ldi     YL, 0           ;[-15] R0 address is 0
+    ldi     YH, 0           ;[-14]
+    ldi     cnt, 2          ;[-13]
+;   rjmp    usbSendAndReti      fallthrough
+
+; USB spec says:
+; idle = J
+; J = (D+ = 0), (D- = 1) or USBOUT = 0x01
+; K = (D+ = 1), (D- = 0) or USBOUT = 0x02
+; Spec allows 7.5 bit times from EOP to SOP for replies (= 60 cycles)
+
+;usbSend:
+;pointer to data in 'Y'
+;number of bytes in 'cnt' -- including sync byte
+;uses: x1...x3, shift, cnt, Y [x1 = mirror USBOUT, x2 = USBMASK, x3 = bitstuff cnt]
+;Numbers in brackets are time since first bit of sync pattern is sent (start of instruction)
+usbSendAndReti:
+    in      x2, USBDDR          ;[-10] 10 cycles until SOP
+    ori     x2, USBMASK         ;[-9]
+    sbi     USBOUT, USBMINUS    ;[-8] prepare idle state; D+ and D- must have been 0 (no pullups)
+    out     USBDDR, x2          ;[-6] <--- acquire bus
+    in      x1, USBOUT          ;[-5] port mirror for tx loop
+    ldi     shift, 0x40         ;[-4] sync byte is first byte sent (we enter loop after ror)
+    ldi     x2, USBMASK         ;[-3]
+doExorN1:
+    eor     x1, x2              ;[-2] [06] [62]
+    ldi     x3, 6               ;[-1] [07] [63]
+commonN1:
+stuffN2Delay:
+    out     USBOUT, x1          ;[00] [08] [64] <--- set bit
+    ror     shift               ;[01]
+    brcc    doExorN2            ;[02]
+    subi    x3, 1               ;[03]
+    brne    commonN2            ;[04]
+    lsl     shift               ;[05] compensate ror after rjmp stuffDelay
+    rjmp    stuffN2Delay        ;[06] after ror, C bit is reliably clear
+doExorN2:
+    eor     x1, x2              ;[04] [12]
+    ldi     x3, 6               ;[05] [13]
+commonN2:
+    nop2                        ;[06] [14]
+    subi    cnt, 171            ;[08] [16] trick: (3 * 171) & 0xff = 1
+    out     USBOUT, x1          ;[09] [17] <--- set bit
+    brcs    txBitloop           ;[10]      [27] [44]
+
+stuff6Delay:
+    ror     shift               ;[45] [53]
+    brcc    doExor6             ;[46]
+    subi    x3, 1               ;[47]
+    brne    common6             ;[48]
+    lsl     shift               ;[49] compensate ror after rjmp stuffDelay
+    nop                         ;[50] stuffing consists of just waiting 8 cycles
+    rjmp    stuff6Delay         ;[51] after ror, C bit is reliably clear
+doExor6:
+    eor     x1, x2              ;[48] [56]
+    ldi     x3, 6               ;[49]
+common6:
+stuff7Delay:
+    ror     shift               ;[50] [58]
+    out     USBOUT, x1          ;[51] <--- set bit
+    brcc    doExor7             ;[52]
+    subi    x3, 1               ;[53]
+    brne    common7             ;[54]
+    lsl     shift               ;[55] compensate ror after rjmp stuffDelay
+    rjmp    stuff7Delay         ;[56] after ror, C bit is reliably clear
+doExor7:
+    eor     x1, x2              ;[54] [62]
+    ldi     x3, 6               ;[55]
+common7:
+    ld      shift, y+           ;[56]
+    nop                         ;[58]
+    tst     cnt                 ;[59]
+    out     USBOUT, x1          ;[60] [00]<--- set bit
+    brne    txByteLoop          ;[61] [01]
+;make SE0:
+    cbr     x1, USBMASK         ;[02] prepare SE0 [spec says EOP may be 15 to 18 cycles]
+    lds     x2, usbNewDeviceAddr;[03]
+    lsl     x2                  ;[05] we compare with left shifted address
+    subi    YL, 2 + 0           ;[06] Only assign address on data packets, not ACK/NAK in r0
+    sbci    YH, 0               ;[07]
+    out     USBOUT, x1          ;[00] <-- out SE0 -- from now 2 bits = 16 cycles until bus idle
+;2006-03-06: moved transfer of new address to usbDeviceAddr from C-Code to asm:
+;set address only after data packet was sent, not after handshake
+    breq    skipAddrAssign      ;[01]
+    sts     usbDeviceAddr, x2   ; if not skipped: SE0 is one cycle longer
+skipAddrAssign:
+;end of usbDeviceAddress transfer
+    ldi     x2, 1<<USB_INTR_PENDING_BIT;[03] int0 occurred during TX -- clear pending flag
+    USB_STORE_PENDING(x2)       ;[04]
+    ori     x1, USBIDLE         ;[05]
+    in      x2, USBDDR          ;[06]
+    cbr     x2, USBMASK         ;[07] set both pins to input
+    mov     x3, x1              ;[08]
+    cbr     x3, USBMASK         ;[09] configure no pullup on both pins
+    lpm                         ;[10]
+    lpm                         ;[13]
+    out     USBOUT, x1          ;[16] <-- out J (idle) -- end of SE0 (EOP signal)
+    out     USBDDR, x2          ;[17] <-- release bus now
+    out     USBOUT, x3          ;[18] <-- ensure no pull-up resistors are active
+    rjmp    doReturn
+
+
+
+/*****************************************************************************
+The following PHP script generates a code skeleton for the receiver routine:
+
+<?php
+
+function printCmdBuffer($thisBit)
+{
+global $cycle;
+
+    $nextBit = ($thisBit + 1) % 8;
+    $s = ob_get_contents();
+    ob_end_clean();
+    $s = str_replace("#", $thisBit, $s);
+    $s = str_replace("@", $nextBit, $s);
+    $lines = explode("\n", $s);
+    for($i = 0; $i < count($lines); $i++){
+        $s = $lines[$i];
+        if(ereg("\\[([0-9-][0-9])\\]", $s, $regs)){
+            $c = $cycle + (int)$regs[1];
+            $s = ereg_replace("\\[[0-9-][0-9]\\]", sprintf("[%02d]", $c), $s);
+        }
+        if(strlen($s) > 0)
+            echo "$s\n";
+    }
+}
+
+function printBit($isAfterSet, $bitNum)
+{
+    ob_start();
+    if($isAfterSet){
+?>
+    ifioclr USBIN, USBMINUS     ;[00] <--- sample
+    rjmp    bit#IsClr           ;[01]
+    andi    shift, ~(7 << #)    ;[02]
+    breq    unstuff#s           ;[03]
+    in      phase, USBIN        ;[04] <- phase
+    rjmp    bit@AfterSet        ;[05]
+unstuff#s:
+    in      phase, USBIN        ;[05] <- phase (one cycle too late)
+    andi    fix, ~(1 << #)      ;[06]
+    nop2                        ;[-1]
+    nop2                        ;[01]
+bit#IsClr:
+    ifrset  phase, USBMINUS     ;[03] check phase only if D- changed
+    lpm                         ;[04]
+    in      phase, USBIN        ;[05] <- phase (one cycle too late)
+    ori     shift, 1 << #       ;[06]
+<?php
+    }else{
+?>
+    ifioset USBIN, USBMINUS     ;[00] <--- sample
+    rjmp    bit#IsSet           ;[01]
+    andi    shift, ~(7 << #)    ;[02]
+    breq    unstuff#c           ;[03]
+    in      phase, USBIN        ;[04] <- phase
+    rjmp    bit@AfterClr        ;[05]
+unstuff#c:
+    in      phase, USBIN        ;[05] <- phase (one cycle too late)
+    andi    fix, ~(1 << #)      ;[06]
+    nop2                        ;[-1]
+    nop2                        ;[01]
+bit#IsSet:
+    ifrclr  phase, USBMINUS     ;[03] check phase only if D- changed
+    lpm                         ;[04]
+    in      phase, USBIN        ;[05] <- phase (one cycle too late)
+    ori     shift, 1 << #       ;[06]
+<?php
+    }
+    printCmdBuffer($bitNum);
+}
+
+$bitStartCycles = array(1, 9, 17, 26, 34, 42, 51, 59);
+for($i = 0; $i < 16; $i++){
+    $bit = $i % 8;
+    $emitClrCode = ($i + (int)($i / 8)) % 2;
+    $cycle = $bitStartCycles[$bit];
+    if($emitClrCode){
+        printf("bit%dAfterClr:\n", $bit);
+    }else{
+        printf("bit%dAfterSet:\n", $bit);
+    }
+    ob_start();
+    echo "    *****                       ;[-1]\n";
+    printCmdBuffer($bit);
+    printBit(!$emitClrCode, $bit);
+    if($i == 7)
+        echo "\n";
+}
+
+?>
+*****************************************************************************/