EZ-8 as a Servo/PWM Controller

For those that are looking for a servo/pwm controller for VSA this program will do the trick. It converts the EZ-8 into a VSA-compatible servo controller that will run six servos (Ch1 - Ch6) and two PWM channels (Ch7 - Ch8).

So, why would you use the EZ-8 for this instead of the Prop-SX?

1) Smaller footprint
2) EZ-8 has a 5A regulator for the 5v outputs (yes, we snuck that in just for this purpose)
   -- that's not to say that 5A will handle all servo apps, but it should handle many if not most small props
3) The selector switch allows you to isloate a channel
   -- 0 : all channels on
   -- 1 to 8 : isolate a channel
   -- 9 : all channels off

The ability to isolate a channel will be helpful when you want to go back and fine-tune the mouth movements of your talking skull without disrupting the whole VSA show.

I've attached a blank VSA (version 4) file for you to start with.

' =========================================================================
'
' File...... EZ-8_Servo.SXB
' Purpose...
' Author.... Jon Williams, EFX-TEK
' Copyright (c) 2009 EFX-TEK
' Some Rights Reserved
' -- see http://creativecommons.org/licenses/by/3.0/
' E-mail.... jwilliams@efx-tek.com
' Started...
' Updated... 24 AUG 2009
'
' =========================================================================

' -------------------------------------------------------------------------
' Program Description
' -------------------------------------------------------------------------
'
' Servo controller/output device designed for use with VSA or other
' real-time serial control programs.
'
' CH1 to CH6... Servo control
' CH7 to CH8... PWM outputs
'
' The protocol is identical to the SEETRON (www.seetron.com) MiniSSC:
'
' <sync><channel><value>
'
' sync...... $FF (255)
'
' channel... 0 to 5 for servos
' 6 to 7 for pwm outputs
'
' value..... 55 to 245 for servos (150 = center)
' 0 to 254 for pwm outputs
'
' Default baud rate is 38.4K but can be changed down to as low as 2400.

' -------------------------------------------------------------------------
' Conditional Compilation Symbols
' -------------------------------------------------------------------------

' -------------------------------------------------------------------------
' Device Settings
' -------------------------------------------------------------------------

ID "EZ8_Srvo"

DEVICE SX28, OSCHS2, BOR42
FREQ 50_000_000

' -------------------------------------------------------------------------
' I/O Pins
' -------------------------------------------------------------------------

Outs PIN RC
Ch8 PIN RC.7 OUTPUT
Ch7 PIN RC.6 OUTPUT
Ch6 PIN RC.5 OUTPUT
Ch5 PIN RC.4 OUTPUT
Ch4 PIN RC.3 OUTPUT
Ch3 PIN RC.2 OUTPUT
Ch2 PIN RC.1 OUTPUT
Ch1 PIN RC.0 OUTPUT

LedGrn PIN RB.7 OUTPUT
LedRed PIN RB.6 OUTPUT
PgmBtn PIN RB.5 INPUT PULLUP
StartBtn PIN RB.4 INPUT PULLUP
MS3 PIN RB.3 INPUT PULLUP
MS2 PIN RB.2 INPUT PULLUP
MS1 PIN RB.1 INPUT PULLUP
MS0 PIN RB.0 INPUT PULLUP

TX PIN RA.3 OUTPUT
RX PIN RA.2 INPUT
SCL PIN RA.1 INPUT
SDA PIN RA.0 INPUT

' -------------------------------------------------------------------------
' Constants
' -------------------------------------------------------------------------

IsOn CON 1
IsOff CON 0

Yes CON 1
No CON 0

LO_LIMIT CON 55 ' to prevent servo burn-up
HI_LIMIT CON 245

' Bit dividers for 3.255 uS interrupt
' -- ISR actually runs at 3.333 uS for better servo timing

Baud2400 CON 128
Baud4800 CON 64
Baud9600 CON 32
Baud19K2 CON 16
Baud38K4 CON 8

Baud1x0 CON Baud38K4 ' 1 bit period (ISR counts)
Baud1x5 CON Baud1x0 * 3 / 2 ' 1.5 bit periods

LED_OFF CON 0
LED_GRN CON 1
LED_RED CON 2
LED_YEL CON 3

' -------------------------------------------------------------------------
' Variables
' -------------------------------------------------------------------------

flags VAR Byte ' (keep global)
isrFlag VAR flags.0
rxReady VAR flags.1 ' rx byte waiting
ledFlash VAR flags.7

btnFlags VAR Byte ' (global)
swMS0 VAR btnFlags.0
swMS1 VAR btnFlags.1
swMS2 VAR btnFlags.2
swMS3 VAR btnFlags.3
btnStart VAR btnFlags.4
btnRec VAR btnFlags.5

pwmTemp VAR Byte

' -------------------------------------------------------------------------

sync VAR Byte
chan VAR Byte
value VAR Byte
mask VAR Byte

tmpW1 VAR Word

rxSerial VAR Byte (16)
rxBuf VAR rxSerial(0) ' 8-byte buffer
rxCount VAR rxSerial(8) ' rx bit count
rxDivide VAR rxSerial(9) ' bit divisor timer
rxByte VAR rxSerial(10) ' recevied byte
rxHead VAR rxSerial(11) ' buffer head (write to)
rxTail VAR rxSerial(12) ' buffer tail (read from)
rxBufCnt VAR rxSerial(13) ' # bytes in buffer

svoData VAR Byte (16) ' bank servo data
pos VAR svoData(0) ' position table
pos0 VAR svoData(0)
pos1 VAR svoData(1)
pos2 VAR svoData(2)
pos3 VAR svoData(3)
pos4 VAR svoData(4)
pos5 VAR svoData(5)
pos6 VAR svoData(6)
pos7 VAR svoData(7)
svoTix VAR svoData(8) ' isr divider
svoFrame_LSB VAR svoData(9) ' frame timer
svoFrame_MSB VAR svoData(10)
svoIdx VAR SvoData(11) ' active servo pointer
svoTimer VAR svoData(12) ' pulse timer
svoPin VAR svoData(13) ' active servo pin

dimmer VAR Byte(4) BANK
level1 VAR dimmer(0)
level2 VAR dimmer(1)
acc1 VAR dimmer(2)
acc2 VAR dimmer(3)

ledCtrl VAR Byte (2) BANK ' LED color / flash ctrl
ledState VAR ledCtrl(0) ' 0-7; off, grn, red, yel
rgTimer VAR ledCtrl(1)

dbControl VAR Byte (4) BANK ' for debounce
ms1Timer_LSB VAR dbControl(0) ' isr ticks/millisecond
ms1Timer_MSB VAR dbControl(1)
btnTimer VAR dbControl(2) ' debounce timer (ms)
btnTemp VAR dbControl(3) ' work var for debounce

' =========================================================================
  INTERRUPT NOPRESERVE 300_000 ' (4) run every 3.333 uS
' =========================================================================

Mark_ISR:
  \ SETB isrFlag ' (1)

' -------
' RX UART
' -------
'
' UART code by C. Gracey, A. Williams, et al
' -- buffer and flow control mods by Jon Williams
'
Receive:
  ASM
   BANK rxSerial ' (1)
   JB rxBufCnt.3, RX_Done ' (2/4) skip if buffer is full
   MOVB C, RX ' (4) sample serial input
   TEST rxCount ' (1) receiving now?
   JNZ RX_Bit ' (2/4) yes, get next bit
   MOV W, #9 ' (1) no, prep for next byte
   SC ' (1/2)
   MOV rxCount, W ' (1) if start, load bit count
   MOV rxDivide, #Baud1x5 ' (2) prep for 1.5 bit periods

RX_Bit:
   DJNZ rxDivide, RX_Done ' (2/4) complete bit cycle?
   MOV rxDivide, #Baud1x0 ' (2) yes, reload bit timer
   DEC rxCount ' (1) update bit count
   SZ ' (1/2)
   RR rxByte ' (1) position for next bit
   SZ ' (1/2)
   JMP RX_Done ' (3)

RX_Buffer:
   MOV W, #rxBuf ' (1) point to buffer head
   ADD W, rxHead ' (1)
   MOV FSR, W ' (1)
   MOV IND, rxByte ' (2) move rxByte to head
   INC rxHead ' (1) update head
   CLRB rxHead.3 ' (1) keep 0..7
   INC rxBufCnt ' (1) update buffer count
   SETB rxReady ' (1) set ready flag

RX_Done:
  ENDASM

' ----------------
' Servo Processing
' ----------------
'
Test_Servo_Tix:
  ASM
   BANK svoData ' (1)
   INC svoTix ' (1) update divider
   CJB svoTix, #3, Servo_Done ' (4/6) done?
   CLR svoTix ' (1) yes, reset for next

' Code below this point runs every 10 uS

Check_Frame_Timer:
   CJNE svoFrame_LSB, #2000 & 255, Inc_FrTmr ' (4/6) svoFrame = 2000 (20 ms)?
   CJNE svoFrame_MSB, #2000 >> 8, Inc_FrTmr ' (4/6)
   CLR svoFrame_LSB ' (1) yes, reset
   CLR svoFrame_MSB ' (1)
   MOV svoPin, #%0000_0001 ' (2) start servo sequence
   CLR svoIdx ' (1) point to servo 0
   MOV FSR, #pos ' (2)
   MOV svoTimer, IND ' (2)
   JMP Refesh_Servo_Outs ' (3)

Inc_FrTmr:
   INC svoFrame_LSB ' (1) DEC svoFrame
   ADDB svoFrame_MSB, Z ' (2)

Check_Servo_Timer:
   TEST svoPin ' (1) any servos on?
   SNZ ' (1)
   JMP Servo_Done ' (1) no, exit
   DEC svoTimer ' (1) yes, update timer
   SZ ' (1) still running?
   JMP Servo_Done ' (1) yes, exit

Reload_Servo_Timer:
   INC svoIdx ' (1) point to next servo
   MOV W, #pos ' (1) get pulse timing
   ADD W, svoIdx ' (1)
   MOV FSR, W ' (1)
   MOV W, IND ' (1)
   MOV svoTimer, W ' (1) move to timer

Select_Next_Servo:
   CLC ' (1)
   RL svoPin ' (1)
   AND svoPin, #%0011_1111 ' (2) limit servo channels

Refesh_Servo_Outs:
   AND Outs, #%1100_0000 ' (2) clear last
   OR Outs, svoPin ' (2) update outputs

Servo_Done:
  ENDASM

' -----------
' PWM Control
' -----------
'
PWM_Control:
  ASM
   BANK dimmer ' (1)
   CLR pwmTemp ' (1) clear work byte
   ADD acc1, level1 ' (2) update accumlator
   RR pwmTemp ' (1) rotate bit into work byte
   ADD acc2, level2 ' (2)
   RR pwmTemp ' (1)
   AND Outs, #%0011_1111 ' (2) clear old bits
   OR Outs, pwmTemp ' (2) update new pwm bits
  ENDASM

' --------------
' LED Controller
' --------------
'
Led_Control:
  ASM
   BANK ledCtrl ' (1)
   MOV W, ledState ' (1) get state
   AND W, #%0000_0011 ' (1) keep legal (0 to 3)
   JMP PC+W ' (3) jump to handler
   JMP Led_0 ' (3)
   JMP Led_1 ' (3)
   JMP Led_2 ' (3)
   JMP Led_3 ' (3)

Led_0: ' LED off
   CLRB LedGrn ' (1)
   CLRB LedRed ' (1)
   JMP Led_Exit ' (3)

Led_1: ' LED green
   SETB LedGrn ' (1)
   CLRB LedRed ' (1)
   JMP Led_Exit ' (3)

Led_3: ' LED yellow
   INC rgTimer ' (1)
   JNB rgTimer.3, Led_1 ' (2/4) 7G:1R
   CLR rgTimer ' (1)

Led_2: ' LED red
   CLRB LedGrn ' (1)
   SETB LedRed ' (1)
   JMP Led_Exit ' (3)

Led_Exit:
  ENDASM

' ------------------------
' Switch / Button Debounce
' ------------------------
'
Check_Inputs:
  ASM
   BANK dbControl ' (1) point to timer
   INC ms1Timer_LSB ' (1)
   ADDB ms1Timer_MSB, Z ' (2)
   CJNE ms1Timer_LSB, #$2C, DB_Exit ' (4/6) at 1ms?
   CJNE ms1Timer_MSB, #$01, DB_Exit ' (4/6)
   CLR ms1Timer_LSB ' (1) yes, re-start
   CLR ms1Timer_MSB

DB_Check:
   INC btnTimer
   CJB btnTimer, #25, DB_Port_Scan ' (2/4) keep scanning for 25ms
   CLR btnTimer ' (1) restart scan timer
   MOV btnFlags, btnTemp ' (2) update program flags
   MOV btnTemp, #%0011_1111 ' (2) reset for next scan
   JMP DB_Exit

DB_Port_Scan:
   MOV W, /RB ' (1) scan port bits (invert)
   AND btnTemp, W ' (1) clear any released

DB_Exit:
  ENDASM

ISR_Exit:
  RETURNINT ' (4)

' -------------------------------------------------------------------------
' Subroutine / Function Declarations
' -------------------------------------------------------------------------

RX_BYTE FUNC 1, 0 ' receive a byte

' =========================================================================
  PROGRAM Start
' =========================================================================

Start:
  TX = 1 ' set TX line to idle

  ' center servos
  PUT pos, 150, 150, 150, 150, 150, 150

Main:
  chan = btnFlags & $0F ' read the selector
  IF chan = 0 THEN ' if 0
   ledState = LED_GRN ' all channels active
  ELSEIF chan < 9 THEN ' if 1-to-8 then
   ledState = LED_YEL ' isolate
  ELSE ' if 10 then
   ledState = LED_RED ' all off
  ENDIF

  READ Isolate + chan, mask ' convert position to TRIS value
  TRIS_C = mask ' update

  IF rxReady = No THEN Main ' if no serial, keep waiting

Get_Sync:
  sync = RX_BYTE
  IF sync <> $FF THEN Main

Get_Channel:
  chan = RX_BYTE
  IF chan = $FF THEN Get_Channel ' correct for re-sync
  IF chan > 7 THEN Main ' check channel range

Get_Value:
  value = RX_BYTE
  IF value = $FF THEN Get_Channel ' correct for re-sync

Process_Value:
  IF chan < 6 THEN ' servo channel?
   value = value MIN LO_LIMIT ' force to legal limits
   value = value MAX HI_LIMIT
   value = HI_LIMIT - value ' invert to match VSA
   value = value + LO_LIMIT
   pos(chan) = value
  ELSE
   tmpW1 = value * value ' linearize; x = (x*x)/256
   value = tmpW1_MSB
   IF chan = 6 THEN
   level1 = value
   ELSE
   level2 = value
   ENDIF
  ENDIF
  GOTO Main

' -------------------------------------------------------------------------
' Subroutine / Function Code
' -------------------------------------------------------------------------

' Use: aByte = RX_BYTE
' -- returns "aByte" from 8-byte circular buffer
' -- will wait if buffer is presently empty
' -- rxBufCnt holds byte count of receive buffer (0 to 8)

FUNC RX_BYTE
  ASM
   JNB rxReady, @$ ' wait if empty
   BANK rxSerial ' point to serial vars
   MOV W, #rxBuf
   ADD W, rxTail ' point to rxBuf(rxTail
   MOV FSR, W
   MOV __PARAM1, IND ' get byte at tail
   INC rxTail ' update tail
   CLRB rxTail.3 ' keep 0..7
   DEC rxBufCnt ' update buffer count
   SNZ ' exit if not zero
   CLRB rxReady ' else clear ready flag
   BANK $00
  ENDASM
  ENDFUNC

' =========================================================================
' User Data
' =========================================================================

Isolate:
  DATA %00_000000 ' all outputs on
  DATA %11_111110 ' isolate ch1
  DATA %11_111101
  DATA %11_111011
  DATA %11_110111
  DATA %11_101111
  DATA %11_011111
  DATA %10_111111
  DATA %01_111111 ' isolate ch8
  DATA %11_111111 ' all off