usbdrv/usbdrvasm128.inc@b84252fe69c6
usbdrv/usbdrvasm128.inc
Fri, 17 Feb 2017 13:26:39 +0100
- author
- mbayer
- date
- Fri, 17 Feb 2017 13:26:39 +0100
- changeset 6
- b84252fe69c6
- parent 0
- 9e9b2c78bd31
- permissions
- -rw-r--r--
changes to run client on windows platform too via libusb dev
/* 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"; } ?> *****************************************************************************/
