Invert Servo32v7 Driver output (Assembly Language)
courtens
Posts: 101
I am stuck trying to invert the output of the driver Servo32v7.
All works well without going through the 7404N inverter chip; but would like to us the chip --- I am having some very high power discharge in a somewhat close proximity of the servos wire which is messing up my signal to the servo. I am hoping this would help.
Looking at the driver code, could it be that I would needs to change this line from 1 to 0? This is the line
I decided to past the driver code here as the Object Exchange Site is undergoing some maintenance.
All works well without going through the 7404N inverter chip; but would like to us the chip --- I am having some very high power discharge in a somewhat close proximity of the servos wire which is messing up my signal to the servo. I am hoping this would help.
Looking at the driver code, could it be that I would needs to change this line from 1 to 0? This is the line
ZoneShift1 res 1
I decided to past the driver code here as the Object Exchange Site is undergoing some maintenance.
{{
*****************************************
* Servo32v7 Driver v7 *
* Author: Beau Schwabe *
* Copyright (c) 2009 Parallax *
* See end of file for terms of use. *
*****************************************
*****************************************************************
Control up to 32-Servos Version 7 08-18-2009
*****************************************************************
Coded by Beau Schwabe (Parallax).
*****************************************************************
History:
Version 1 - initial concept
Version 2 - (03-08-2006) Beta release
Version 3 - (11-04-2007) Improved servo resolution to 1uS
Version 4 - (05-03-2009) Ability to disable a servo channel
and remove channel preset requirement
Version 5 - (05-08-2009) Added ramping ability
Version 6 - (07-18-2009) Fixed slight timing skew in ZoneLoop and
fixed overhead timing latency in ZoneCore
Version 7 - (08-18-2009) Fixed servo jitter in ramping function when
servo reached it's target position.
Theory of Operation:
Each servo requires a pulse that varies from 1mS to 2mS with a period of 20mS.
To prevent a current surge nightmare, I have broken the 20mS period into four
groups or Zones of 8 servos each with a period of 5mS. What this does, is to
ensure that at any given moment in time, a maximum of only 8 servos are receiving
a pulse.
Zone1 Zone2 Zone3 Zone4 In Zone1, servo pins 0- 7 are active
 In Zone2, servo pins 8-15 are active
│─5mS│─5mS│─5mS│─5mS│ In Zone3, servo pins 16-23 are active
│──────────20mS───────────│ In Zone4, servo pins 24-31 are active
   
 1-2mS servo pulse 
The preferred circuit of choice is to place a 4.7K resistor on each signal input
to the servo. If long leads are used, place a 1000uF cap at the servo power
connector. Servo's seem to be happy with a 5V supply receiving a 3.3V signal.
}}
CON
_1uS = 1_000_000 / 1 'Divisor for 1 uS
ZonePeriod = 5_000 '5mS (1/4th of typical servo period of 20mS)
NoGlitchWindow = 3_000 '3mS Glitch prevention window (set value larger than maximum servo width of 2.5mS)
'Use at least 500uS for overhead (actual overhead about 300uS)
LowRange = 500 '<- during Debug I changed this value to 1 to test 1us resolution
HighRange = 2500
VAR
long RampFlag
long ZoneClocks
long NoGlitch
long ServoPinDirection
long ServoData[32] '0-31 Current Servo Value
long ServoTarget[32] '0-31 Desired Servo Value
long ServoDelay[32] '0-31 Servo Ramp Delay
OBJ
SERVO : "Servo32_Ramp_v2"
PUB Start
RampFlag := 0
ZoneClocks := (clkfreq / _1uS * ZonePeriod) 'calculate # of clocks per ZonePeriod
NoGlitch := $FFFF_FFFF-(clkfreq / _1uS * NoGlitchWindow) 'calculate # of clocks for GlitchFree servos. Problem occurs when 'cnt' value rollover is less than the servo's pulse width.
cognew(@ServoStart,@ZoneClocks)
PUB Ramp
SERVO.StartRamp(@ServoData)
RampFlag := 1
PUB SetRamp(Pin, Width,Delay)|S_Width
ServoDelay[Pin] := Delay 'Note: The resolution of Delay is about 38.75us
' or 3100 clocks
S_Width := LowRange #> Width <# HighRange 'limit Width value
Pin := 0 #> Pin <# 31 'limit Pin value between 0 and 31
ServoTarget[Pin] := ((clkfreq / _1uS * S_Width)/SERVO#CoreSpeed)*SERVO#CoreSpeed
'calculate # of clocks for a specific Pulse Width
'and adjust the snap value to match the value of
'CoreSpeed. (Note: this prevents jitter when Servo
' has reached it's target position)
if S_Width==Width
dira[Pin] := 1 'set selected servo pin as an OUTPUT
else
dira[Pin] := 0 'set selected servo pin as an INPUT only if Width out of range
ServoPinDirection := dira 'Read I/O state of ALL pins
PUB Set(Pin, Width)|S_Width 'Set Servo value
S_Width := LowRange #> Width <# HighRange 'limit Width value
Pin := 0 #> Pin <# 31 'limit Pin value between 0 and 31
if RampFlag == 0
ServoData[Pin] := (clkfreq / _1uS * S_Width) 'calculate # of clocks for a specific Pulse Width
else
ServoData[Pin] := ((clkfreq / _1uS * S_Width)/SERVO#CoreSpeed)*SERVO#CoreSpeed
ServoTarget[Pin] := ServoData[Pin]
if S_Width==Width
dira[Pin] := 1 'set selected servo pin as an OUTPUT
else
dira[Pin] := 0 'set selected servo pin as an INPUT only if Width out of range
ServoPinDirection := dira 'Read I/O state of ALL pins
DAT
'*********************
'* Assembly language *
'*********************
org
'------------------------------------------------------------------------------------------------------------------------------------------------
ServoStart mov Index, par 'Set Index Pointer
rdlong _ZoneClocks, Index 'Get ZoneClock value
add Index, #4 'Increment Index to next Pointer
rdlong _NoGlitch, Index 'Get NoGlitch value
add Index, #4 'Increment Index to next Pointer
mov PinDirectionAddress, Index 'Set pointer for I/O direction Address
add Index, #32 'Increment Index to END of Zone1 Pointer
mov Zone1Index, Index 'Set Index Pointer for Zone1
add Index, #32 'Increment Index to END of Zone2 Pointer
mov Zone2Index, Index 'Set Index Pointer for Zone2
add Index, #32 'Increment Index to END of Zone3 Pointer
mov Zone3Index, Index 'Set Index Pointer for Zone3
add Index, #32 'Increment Index to END of Zone4 Pointer
mov Zone4Index, Index 'Set Index Pointer for Zone4
IOupdate rdlong dira, PinDirectionAddress 'Get and set I/O pin directions
'------------------------------------------------------------------------------------------------------------------------------------------------
Zone1 mov ZoneIndex, Zone1Index 'Set Index Pointer for Zone1
call #ResetZone
call #ZoneCore
Zone2 mov ZoneIndex, Zone2Index 'Set Index Pointer for Zone2
call #IncrementZone
call #ZoneCore
Zone3 mov ZoneIndex, Zone3Index 'Set Index Pointer for Zone3
call #IncrementZone
call #ZoneCore
Zone4 mov ZoneIndex, Zone4Index 'Set Index Pointer for Zone4
call #IncrementZone
call #ZoneCore
jmp #IOupdate
'------------------------------------------------------------------------------------------------------------------------------------------------
ResetZone mov ZoneShift1, #1
mov ZoneShift2, #2
mov ZoneShift3, #4
mov ZoneShift4, #8
mov ZoneShift5, #16
mov ZoneShift6, #32
mov ZoneShift7, #64
mov ZoneShift8, #128
ResetZone_RET ret
'------------------------------------------------------------------------------------------------------------------------------------------------
IncrementZone shl ZoneShift1, #8
shl ZoneShift2, #8
shl ZoneShift3, #8
shl ZoneShift4, #8
shl ZoneShift5, #8
shl ZoneShift6, #8
shl ZoneShift7, #8
shl ZoneShift8, #8
IncrementZone_RET ret
'------------------------------------------------------------------------------------------------------------------------------------------------
ZoneCore mov ServoByte, #0 'Clear ServoByte
mov Index, ZoneIndex 'Set Index Pointer for proper Zone
ZoneSync mov SyncPoint, cnt 'Create a Sync Point with the system counter
' mov temp, _NoGlitch
' sub temp, SyncPoint wc
sub _NoGlitch, SyncPoint nr,wc 'Test to make sure 'cnt' value won't rollover within Servo's pulse width
if_C jmp #ZoneSync 'If C flag is set get a new Sync Point, otherwise we are ok.
' add SyncPoint, #220 '<- Debug - 2us becomes 1us
' add SyncPoint, #300 '<- Debug - 2us becomes 3us
add SyncPoint, #260 'Add overhead offset to counter Sync point
'midpoint from above Debug test.
mov LoopCounter, #8 'Set Loop Counter to 8 Servos for this Zone
movd LoadServos, #ServoWidth8 'Restore/Set self-modifying code on "LoadServos" line
movd ServoSync, #ServoWidth8 'Restore/Set self-modifying code on "ServoSync" line
LoadServos rdlong ServoWidth8, Index 'Get Servo Data
sub Index, #4 'Decrement Index pointer to next address
nop
ServoSync add ServoWidth8, SyncPoint 'Determine system counter location where pulse should end
sub LoadServos, d_field 'self-modify destination pointer for "LoadServos" line
sub ServoSync, d_field 'self-modify destination pointer for "ServoSync" line
djnz LoopCounter, #LoadServos 'Do ALL 8 servo positions for this Zone
mov temp, _ZoneClocks 'Move _ZoneClocks into temp
add temp, SyncPoint 'Add SyncPoint to _ZoneClocks
'----------------------------------------------Start Tight Servo code-------------------------------------------------------------
ZoneLoop mov tempcnt, cnt '(4 - clocks) take a snapshot of current counter value
cmpsub ServoWidth1, tempcnt nr,wc '(4 - clocks) compare system counter to ServoWidth ; write result in C flag
muxc ServoByte, ZoneShift1 '(4 - clocks) Set ServoByte.Bit0 to "0" or "1" depending on the value of "C"
cmpsub ServoWidth2, tempcnt nr,wc '(4 - clocks) compare system counter to ServoWidth ; write result in C flag
muxc ServoByte, ZoneShift2 '(4 - clocks) Set ServoByte.Bit1 to "0" or "1" depending on the value of "C"
cmpsub ServoWidth3, tempcnt nr,wc '(4 - clocks) compare system counter to ServoWidth ; write result in C flag
muxc ServoByte, ZoneShift3 '(4 - clocks) Set ServoByte.Bit2 to "0" or "1" depending on the value of "C"
cmpsub ServoWidth4, tempcnt nr,wc '(4 - clocks) compare system counter to ServoWidth ; write result in C flag
muxc ServoByte, ZoneShift4 '(4 - clocks) Set ServoByte.Bit3 to "0" or "1" depending on the value of "C"
cmpsub ServoWidth5, tempcnt nr,wc '(4 - clocks) compare system counter to ServoWidth ; write result in C flag
muxc ServoByte, ZoneShift5 '(4 - clocks) Set ServoByte.Bit4 to "0" or "1" depending on the value of "C"
cmpsub ServoWidth6, tempcnt nr,wc '(4 - clocks) compare system counter to ServoWidth ; write result in C flag
muxc ServoByte, ZoneShift6 '(4 - clocks) Set ServoByte.Bit5 to "0" or "1" depending on the value of "C"
cmpsub ServoWidth7, tempcnt nr,wc '(4 - clocks) compare system counter to ServoWidth ; write result in C flag
muxc ServoByte, ZoneShift7 '(4 - clocks) Set ServoByte.Bit6 to "0" or "1" depending on the value of "C"
cmpsub ServoWidth8, tempcnt nr,wc '(4 - clocks) compare system counter to ServoWidth ; write result in C flag
muxc ServoByte, ZoneShift8 '(4 - clocks) Set ServoByte.Bit7 to "0" or "1" depending on the value of "C"
mov outa, ServoByte '(4 - clocks) Send ServoByte to Zone Port
cmp temp, tempcnt nr,wc '(4 - clocks) Determine if cnt has exceeded width of _ZoneClocks ; write result in C flag
if_NC jmp #ZoneLoop '(4 - clocks) if the "C Flag" is not set stay in the current Zone
'-----------------------------------------------End Tight Servo code--------------------------------------------------------------
' Total = 80 - clocks @ 80MHz that's 1uS resolution
ZoneCore_RET ret
'------------------------------------------------------------------------------------------------------------------------------------------------
d_field long $0000_0200
PinDirectionAddress long 0
counter long 0
Address1 long 0
Address2 long 0
Address3 long 0
temp1 long 0
temp2 long 0
tempcnt long 0
dly long 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
long 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
ServoWidth1 res 1
ServoWidth2 res 1
ServoWidth3 res 1
ServoWidth4 res 1
ServoWidth5 res 1
ServoWidth6 res 1
ServoWidth7 res 1
ServoWidth8 res 1
ZoneShift1 res 1
ZoneShift2 res 1
ZoneShift3 res 1
ZoneShift4 res 1
ZoneShift5 res 1
ZoneShift6 res 1
ZoneShift7 res 1
ZoneShift8 res 1
temp res 1
Index res 1
ZoneIndex res 1
Zone1Index res 1
Zone2Index res 1
Zone3Index res 1
Zone4Index res 1
SyncPoint res 1
ServoByte res 1
LoopCounter res 1
_ZoneClocks res 1
_NoGlitch res 1
_ServoPinDirection res 1
DAT
{{
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│ TERMS OF USE: MIT License │
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}}
Comments
muxc ServoByte
... so that they read ...
muxnc ServoByte
These lines are located directly after the "ZoneLoop" towards the end of the assembly program.
Also, please update your driver to Servo32v9...
http://forums.parallax.com/showthread.php/147219-CODE-UPDATE-Servo32v9?highlight=servo32v9
Thank you Beau -- changing this in the code inverted the duration length, but not the I/O output.
So in other words what used to be long is now short and what used to be short is now long. The high is still high, and the low is still low.
Maybe I wasn't clear. What I am looking for is to invert the IO output so that high gets to be low and low turns into high.
I was hoping the Bitwise NOT flag would work. As far as I understand the code this would invert the saved values ... (but this is not working.)
Thank you kuroneko. I tried that, but it is not changing anything.
I am new to Assembly Language and can't find what keeps the ON - ON and the OFF - OFF
I assume this is saved in 0 and 1 values within registers -- values that are being called upon.
I tried adding this line; but that just creates chaos:
ZoneLoop ... andn ServoByteInvert, ServoByte '<< new mov outa, ServoByteInvert '(4 - clocks) Send ServoByte to Zone PortVery nice!
I like the way you're thinking -- out of the box!
This is what I'll do.
The lines that I had originally said to change from muxc to muxnc still need to be changed in addition to one more line.
The line that reads ...
ZoneCore mov ServoByte, #0
...should be changed to....
ZoneCore mov ServoByte, #%11111111 <-- EDIT: Don't use this
ZoneCore neg ServoByte, #1
Beau -- Thank you for taking the time to upload this new inverted version. I tried it, but somehow it is still not working. Did it work for you?
EDIT: I just tested it with the attached circuit using the inverted servo driver and the servo worked just fine.
I tested your suggested code only using one servo (at first) -- then with 2 servos. They are "parallax standard servos." Your suggested code is somehow not working, for me.
Here are two images from my scope. Both readings are straight from the propeller pin -- none are going through an inverter.
This is the image of the non-inverting code (v7), which works -- but it is not inverted.
And this is the new driver that isn't working (servo is not moving) and it is also not inverted.
Thanks for the compliment. Not really "out of the box" thinking, just a preference for simplicity. After all if you need a buffer it may as well be one that provides the output polarity you need, and most of the 74xx series logic had inverting and non inverting versions of each chip.
Change "Zonecore" so that it reads "ZoneCore neg ServoByte, #1" and all four zones will work correctly.
Updated code in post #8
IOupdate rdlong dira, PinDirectionAddress ' Get and set I/O pin directions [COLOR="#FFA500"]test invalid, dira wz[/COLOR] ' check for invalid bits [COLOR="#FFA500"] if_nz hubop $, #128[/COLOR] ' reset ... [COLOR="#FFA500"]invalid long $00000003[/COLOR] ' contains a 1 at invalid bit locations (here 0 and 1)If a reset is too extreme simply stop there (waitpeq $, #0) and/or light an LED.PUB SetRamp(Pin, Width,Delay)|S_Width ServoDelay[Pin] := Delay 'Note: The resolution of Delay is about 38.75us ' or 3100 clocks S_Width := LowRange #> Width <# HighRange 'limit Width value Pin := 0 #> Pin <# 31 'limit Pin value between 0 and 31 ServoTarget[Pin] := ((clkfreq / _1uS * S_Width)/SERVO#CoreSpeed)*SERVO#CoreSpeed 'calculate # of clocks for a specific Pulse Width 'and adjust the snap value to match the value of 'CoreSpeed. (Note: this prevents jitter when Servo ' has reached it's target position) [COLOR="#FFA500"] if S_Width==Width ServoPinDirection |= |< Pin 'set selected servo pin as an OUTPUT else ServoPinDirection &= !|< Pin 'set selected servo pin as an INPUT only if Width out of range [/COLOR] PUB Set(Pin, Width)|S_Width 'Set Servo value S_Width := LowRange #> Width <# HighRange 'limit Width value Pin := 0 #> Pin <# 31 'limit Pin value between 0 and 31 if RampFlag == 0 ServoData[Pin] := (clkfreq / _1uS * S_Width) 'calculate # of clocks for a specific Pulse Width else ServoData[Pin] := ((clkfreq / _1uS * S_Width)/SERVO#CoreSpeed)*SERVO#CoreSpeed ServoTarget[Pin] := ServoData[Pin] [COLOR="#FFA500"] if S_Width==Width ServoPinDirection |= |< Pin 'set selected servo pin as an OUTPUT else ServoPinDirection &= !|< Pin 'set selected servo pin as an INPUT only if Width out of range [/COLOR]This never came up with the non-inverted driver because unused outputs (enabled or not) are kept on idle (low). That said, the caller could subsequently clear its dira assignment (as it owns it) which would affect previously set servo pins during the next Set* call. So this needs to be fixed in either version.