---
title: "V-F Data Acquisition"
id: 72220
type: "computer_media"
slug: "v-f-data-acquisition"
url: "http://localhost/computer_media/v-f-data-acquisition/"
markdown_url: "http://localhost/computer_media/v-f-data-acquisition.md"
published_at: "2026-10-23T01:07:37+00:00"
modified_at: "2026-10-23T01:07:38+00:00"
author: "David Anderson"
featured_image:
  url: "http://localhost/wp-content/uploads/2026/10/vdaq-hr.png"
excerpt: "Logs analog voltages through a voltage-to-frequency converter on the EAR jack, storing up to 2048 samples and plotting, listing or printing them on the TS2040."
category:
  - name: "Archived Media"
    slug: "archived-media"
    taxonomy: "category"
    url: "http://localhost/category/archived-media/"
post_tag:
  - name: "Downloadable"
    slug: "downloadable"
    taxonomy: "post_tag"
    url: "http://localhost/tag/downloadable/"
  - name: "Silicon Mountain Computers"
    slug: "silicon-mountain-computers"
    taxonomy: "post_tag"
    url: "http://localhost/tag/silicon-mountain-computers/"
  - name: "TS 1000"
    slug: "ts1000"
    taxonomy: "post_tag"
    url: "http://localhost/tag/ts1000/"
model:
  - name: "Timex/Sinclair 1000"
    slug: "ts-1000"
    taxonomy: "model"
    url: "http://localhost/model/ts-1000/"
indiv:
  - name: "Fred Nachbaur"
    slug: "fred-nachbaur"
    taxonomy: "indiv"
    url: "http://localhost/indiv/fred-nachbaur/"
genre:
  - name: "Science"
    slug: "science"
    taxonomy: "genre"
    url: "http://localhost/type/science/"
media_type: "Program"
programmers:
  - name: "Fred Nachbaur"
    slug: "fred-nachbaur"
    taxonomy: "indiv"
    url: "http://localhost/indiv/fred-nachbaur/"
download_url: "https://archive.org/download/timex-sinclair-software-archive/V-F%20Data%20Acquisition%281986%29%28F.%20Nachbaur%29%28TS1000%29%28US%29%28Program%29.zip"
mediadate: "1985"
producer_company:
  - id: 20332
    title: "Silicon Mountain Computers"
    type: "company"
    url: "http://localhost/company/silicon-mountain-computers/"
images:
  - url: "http://localhost/wp-content/uploads/2026/10/vdaq-hr.png"
  - url: "http://localhost/wp-content/uploads/2026/10/vdaq-1.png"
  - url: "http://localhost/wp-content/uploads/2026/10/vdaq-label.jpg"
article_media:
  - id: 60318
    title: "VDAQ – A Data Acquisition Development Program"
    type: "article"
    url: "http://localhost/article/vdaq-a-data-acquisition-development-program/"
media_type_tags: "Science"
---

# V-F Data Acquisition

Turns a TS1000 or ZX81 into a data logger by reading an analog voltage through a voltage-to-frequency (V-F) converter wired to the EAR jack. Machine code counts the pulses in a timed window, and the count is proportional to the input voltage. A 4096-byte string holds 32 “screens” of 64 two-byte samples, with sample rates from about 3 ms to 1 second. Faster rates give 8-bit resolution and the slowest give about 14-bit. The menu acquires one screen or a run of several screens, plots a screen, prints the values in two columns, resets the plot limits, recalibrates, and draws a long “side-winder” strip chart on the TS2040 printer. Acquisition can start on a keypress, or when the input frequency becomes non-zero or drops to zero.

The program is Fred Nachbaur’s “V-F Data Acquisition 1”. His article “[VDAQ – A Data Acquisition Development Program](http://localhost/article/vdaq-a-data-acquisition-development-program/)” covers the theory, an LM331 V-F circuit, use with the VOTEM analog interface and the program itself. The REMs and title screen give program 1, version 1.3, ©1984. The archive’s file name gives 1986. The zip also has a hi-res version, VDAQ1-HR, version 1.40, dated 1985.

## Program Analysis

### Program Structure

- Line 0: a 407-byte `REM` holding the machine code. Lines 4–7 reset the automatic-listing pointers so line 0 can’t jam the listing.
- Lines 500–620: the menu. `GOTO N2*H5*VAL Z$` jumps to 1000 × the option number.
- Lines 1000–1290: acquire a screen. The time base is converted into a 16-bit loop count and the acquisition routine runs at `USR 16594`. Key start, non-zero start and zero start are handled at 1220 and 1260.
- Lines 2000–2160: plot a screen. Machine code at 16636 draws the axes and the routine at 16776 plots the points, scaled between the plot limits.
- Lines 3000–3190: print the 64 values of a screen as time in ms and voltage, in two columns.
- Lines 4000–4090: set the minimum and maximum plot voltages.
- Lines 5000–5450: initialize. Sets the constants and `DIM D$(4096)`, then calibrates the voltage against a measured reference and the time base against a stopwatch.
- Lines 6000–6070: multi-screen acquisition. Lines 7000–7380: the side-winder plot, which `SCROLL`s and `PLOT`s two samples per row and `COPY`s every 22 rows, with a dry-run option that shows it on screen only.
- Lines 7900–8460: subroutines: choose a screen, choose a count, a two-digit input routine that needs no ENTER, store and fetch the per-screen timing values, and a COPY/continue prompt.
- Lines 9970–9999: save and stop.

### Hi-Res Version

VDAQ1-HR (version 1.40, ©1985) moves the machine code up to around 25000 and adds hi-res routines (`HRM` and `LRM`) that switch between a hi-res graph and the normal display. It plots 1, 2 or 4 files across the full screen, prints labels into the hi-res screen one character at a time through the routine at lines 4–9, has a reverse-video option, and uses its own COPY routine. Data is organized into 16 files instead of 32, and the side-winder plot is gone. Its initialization doesn’t set the constants, which are kept in the saved variables. A REM warns “DONT USE RUN” and says to restart with `GOTO 500`.

### Notable Techniques

- The voltage comes in through the EAR jack as a pulse train, so the only hardware needed besides the V-F converter is a single input bit.
- Small constants (`N0`, `N1`, `N2`, `O0`, `TFS`, `H5`) and subroutine addresses (`FI`, `FS`, `CO`, `AQ`) are kept in variables to save memory.
- To split a number into two bytes for POKEing into the machine code, `RAND` stores it in SEED and the two bytes are read back from 16434/16435. This doesn’t work for zero, so the low plot limit is split arithmetically at lines 2120–2130.
- Line 1150 picks the start mode with one computed jump: `GOTO 1140+(80 AND Z$="K")+(120 AND (Z$="N" OR Z$="Z"))`.
- Line 9999 POKEs 16384 so that the program ends without a report code. The article credits this trick to SYNAPSE.
- The routine at 8000 takes a two-digit screen number without ENTER, or one digit followed by ENTER.

### Potential Issues

- Menu option 0 passes the range check at line 600 and runs `GOTO 0`, which drops into the initialization at line 5000 and re-dimensions `D$`, losing any acquired data.
- In the hi-res version, line 4090 reads `GOTO VAL "400£"`, which can’t be evaluated. It was probably meant to be 4000.

## Source Code

```
   0 REM [D][A][T][A]█[A][Q][.][F][N][1][9][8][4] V 1.3  ▘  ) COPY COPY.#[N]C><= RETURN▛K PLOT ▀.#[N]C▛<= RETURN▛S PLOT / DIM TAN YRNDEEXP INKEY$ 6EXP INKEY$ MSQR INKEY$ LN [/]RNDEEXP INKEY$ #7#7USQR INKEY$ XCOS / DIM USGN INKEY$ XCOS MSGN INKEY$ LN [Q]RND6EXP INKEY$ / LIST  Y█E(RND)▞ ; GOSUB #ATN INKEY$ ",,XC▝/ IF 6EXP INKEY$ TAN  )5 E£RND7Y=Q.;XC▝/ SAVE Y4Q.7XCOS / RAND  :▘#[E] NEW█#STR$ LN #INKEY$  STOPLN #INKEY$  FOR  LPRINT #[B]CQ#[L] FAST GOSUB # GOSUB # FASTAT SGN 5  RZ PRINT ##2▒DK▌[?] GOSUB #/,,▗ GOSUB #S▀ GOSUB PIXW14 GOTO # LET K LLIST ACS #4▘ FOR ACS #COS /"LN #INKEY$ ACS (SQR /▀#▛SQR  FOR [B] GOSUB # GOSUB #TAN VAL ▞(##▌: DACS )*K▘;( RUN AT TAN  Y MSQR INKEY$ EEXP INKEY$ - #;;#7#VAL  LPRINT  GOSUB #USR INKEY$  GOSUB #S3 GOSUB #ABS INKEY$ LN *INKEY$   77# RETURN S?# RETURNGK~~#USQR INKEY$ #Y█LN [M]"USQR INKEY$ W RETURNRNDCOS /[Z]  £ [£]#Z▘/     #D THEN#5▖5▖5▖5▖5▖5▖5▖5▖[X] RUN  COPY COPYLN  LN  LN  LN  LN  LN  LN  LN  LN  LN  LN  LN  LN  LN  LN  LN  LN  LN  LN  LN   
   4 POKE 16394,8
   5 POKE 16395,0
   6 POKE 16419,8
   7 POKE 16420,0
   8 REM [V][-][F]█[D][A][T][A]█[A][C][Q][U][I][S][I][T][I][O][N]█[1]
   9 REM   BY F.NACHBAUR 1984
  10 GOTO 5000
  12 REM 
  15 REM  [G][O][T][O]█[5][0][0]█[T][O]█[R][E][S][T][A][R][T]
 500 CLS
 510 POKE BL,N0
 520 SLOW
 530 PRINT TAB 6;"[V][-][F]█[D][A][T][A]█[A][C][Q][U][I][S][I][T][I][O][N]",,,TAB 6;"PROGRAM 1, V 1.3";TAB 6;"SAMPLE RATE 3-1000 MSEC.",,,L$;TAB 3;"(C)1984","BY F.NACHBAUR",L$
 540 PRINT ,,"[C][H][O][O][S][E]█[A][N]█[O][P][T][I][O][N][:]",,,"1. ACQUIRE DATA (SINGLE SCREEN)","2. PLOT DATA",,"3. PRINT DATA",,L$;"4. RE-SET PLOT LIMITS","5. INITIALIZE",,L$;"6. MULTI-SCREEN ACQUISITION","7. SIDE-WINDER PLOT (TS2040)",L$,,"A. STOP","S. SAVE "
 550 IF INKEY$ ="" THEN GOTO 550
 560 LET Z$=INKEY$ 
 570 POKE BL,N2
 580 IF Z$="S" THEN GOTO 9970
 590 IF Z$="A" THEN GOTO 9990
 600 IF Z$>"7" OR Z$<"0" THEN GOTO H5
 610 CLS
 620 GOTO N2*H5*VAL Z$
1000 REM [A][C][Q][U][I][R][E]█[D][A][T][A]
1010 LET N=N1
1020 GOSUB FI
1030 POKE 16849,N+N1
1040 PRINT "ENTER TIME BASE (.1-";TREF;" SEC): ";
1050 INPUT TB
1060 IF TB<.1 OR TB>TREF THEN GOTO 1050
1070 LET C0=(65535*TB/TREF)
1080 RAND C0
1090 POKE 16540,PEEK S1
1100 POKE 16541,PEEK S2
1110 GOSUB FS
1120 PRINT TB
1130 PRINT ,,"START BY [K]EY OR [N]ON-[Z]ERO INPUT ?"
1140 LET Z$=INKEY$ 
1150 GOTO 1140+(80 AND Z$="K")+(120 AND (Z$="N" OR Z$="Z"))
1160 FAST
1170 RAND USR AQ
1180 SLOW
1190 PRINT AT 21,N0;"==[D][A][T][A]██[A][C][Q][U][I][R][E][D]=="
1200 GOSUB CO
1210 GOTO H5
1220 PRINT AT 21,N0;"[A][N][Y]█[K][E][Y]█[T][O]█[A][C][Q][U][I][R][E]"
1230 IF INKEY$ <>"" THEN GOTO 1230
1240 IF INKEY$ ="" THEN GOTO 1240
1250 GOTO 1160
1260 PRINT AT 21,N0;"CHECKING..."
1270 LET C=USR 16536
1280 IF (C AND Z$="N") OR (NOT C AND Z$="Z") THEN GOTO 1160
1290 GOTO 1270
2000 REM [P][L][O][T]
2010 CLS
2020 GOSUB FI
2030 GOSUB FR
2040 LET R=INT ((CH-CL)/40)
2050 CLS
2060 PRINT (" "+STR$ PH+" V ---------------------------")( TO 32)
2070 RAND USR 16636
2075 POKE BL,N0
2080 PRINT AT O0,N0;"*";AT 21,N0;PL;TAB O0;"<---TIME--->";TAB 27;TB;TAB 14;"[F][I][L][E]:";FL
2085 POKE BL,N2
2090 RAND R
2100 POKE 16850,PEEK S1
2110 POKE 16851,PEEK S2
2120 POKE 16853,INT (CL/TFS)
2130 POKE 16852,CL-TFS*PEEK 16853
2140 RAND USR 16776
2150 GOSUB CO
2160 GOTO H5
3000 REM [P][R][I][N][T]
3010 GOSUB FI
3020 FAST
3030 GOSUB FR
3040 CLS
3050 PRINT ,,"FILE NO:",FL,"TIME BASE   =",TB;" SEC.","SAMPLE RATE = ";SR;" MSEC",L$,,"[N][O]█[M][S][E][C]█[V][O][L][T][A][G][E]██[N][O]█[M][S][E][C]█[V][O][L][T][A][G][E]",,
3060 LET DP=O0**INT (.2+LN CM/LN O0)
3070 FOR A=N1 TO 32
3080 FAST
3090 LET D=N2*(A-N1)+PEEK 16846+TFS*PEEK 16847
3100 LET VL=(PEEK D+TFS*PEEK (D+1))/CM
3110 LET VL=(INT (VL*DP))/DP
3120 LET VH=(PEEK (D+64)+TFS*PEEK (D+65))/CM
3130 LET VH=(INT (VH*DP))/DP
3140 PRINT A;TAB 3;INT (A*SR+N1/N2);TAB 9;VL;TAB 16;"▌";A+32;TAB 20;INT ((A+32)*SR+N1/N2);TAB 26;VH
3150 IF A=14 THEN GOSUB CO
3160 IF A=14 THEN CLS
3170 NEXT A
3180 GOSUB CO
3190 GOTO H5
4000 PRINT "PRESENT LIMITS:",,"MIN. VOLTAGE=";PL,"MAX. VOLTAGE=";PH
4010 PRINT ,,"CHANGE TO:",,"MIN.=";
4020 INPUT PL
4030 PRINT PL,,"MAX.=";
4040 INPUT PH
4050 PRINT PH,,"OK?"
4060 IF INKEY$ ="" THEN GOTO 4060
4070 IF INKEY$ ="Y" THEN GOTO H5
4080 CLS
4090 GOTO 4000
5000 PRINT "[I][N][I][T][I][A][L][I][Z][E][:]"
5010 DIM D$(4096)
5020 LET L$="▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀"
5030 LET N0=0
5040 LET N1=1
5050 LET N2=2
5060 LET O0=10
5070 LET TFS=256
5080 LET S1=16434
5090 LET S2=16435
5100 LET H5=500
5110 LET BL=16418
5120 LET FI=7900
5130 LET SS=7950
5140 LET FS=8200
5150 LET FR=8300
5160 LET CO=8400
5170 LET AQ=16594
5180 LET PL=N0
5190 LET PH=N1
5200 LET N=N1
5210 PRINT "SET SW. 3,6,7; MEASURE VREF",,,"VREF=";
5220 INPUT VREF
5230 PRINT VREF
5240 POKE 16540,255
5250 POKE 16541,255
5260 FAST
5270 LET C=USR 16536
5280 SLOW
5290 PRINT ,,"  MAX COUNT=";C
5300 LET C1=C/VREF
5310 PRINT "1V COUNT AT MAX TIME=";C1;"        "
5320 PRINT ,,"SET TIME-BASE; PRESS ENTER WHEN    READY, NOTE TIME WHEN DISPLAY   RE-APPEARS."
5330 IF INKEY$ <>CHR$ 118 THEN GOTO 5330
5340 FAST
5350 LET FL=N1
5360 GOSUB 7915
5370 LET C0=65535
5380 GOSUB FS
5390 PRINT "LAST COUNT=";USR 16566
5400 SLOW
5410 PRINT ,,"TIME=?";
5420 INPUT TREF
5430 PRINT TREF
5440 GOSUB CO
5450 GOTO H5
6000 REM [M][U][L][T][I][-][A][Q]
6010 CLS
6020 PRINT "START AT "
6030 GOSUB FI
6040 PRINT 
6050 GOSUB SS
6055 IF FL+N>33 THEN GOTO 6000
6060 PRINT ,,,,"(EACH SCREEN)="
6070 GOTO 1030
7000 REM [S][I][D][E][-][P][L][O][T]
7010 GOSUB FI
7020 GOSUB SS
7025 IF FL+N>33 THEN GOTO 7000
7030 GOSUB FR
7040 LET R=((CH-CL)/60)
7050 LET DR=N0
7060 PRINT ,,"DRY RUN?"
7070 IF INKEY$ <>"" THEN GOTO 7070
7080 IF INKEY$ ="" THEN GOTO 7080
7090 IF INKEY$ ="Y" THEN LET DR=N1
7100 FAST
7110 IF NOT DR THEN LPRINT ,,"TB=";TB;" SEC PER SCREEN","SAMPLE RATE=";SR;" MSEC.","TOTAL TIME=";N*TB;" SEC"
7120 IF NOT DR THEN LPRINT ,,STR$ PL;"=MIN.     VOLTS";TAB 21;"MAX.=";PH
7130 LET D=PEEK 16846+TFS*PEEK 16847
7140 LET F=FL
7150 LET C=N0
7160 LET L=N0
7170 LET TM=N0
7180 FOR L=L TO L+21
7190 SCROLL
7200 IF L>=32*N THEN GOTO 7340
7210 PRINT AT 21,30;".";CHR$ (O0*NOT TM);AT 21,N0;"T";AT 21,N0;(CHR$ (F+156)+"----.----+----.----+----.----I") AND NOT C
7220 FOR Y=N1 TO N0 STEP -N1
7230 LET B=PEEK D+TFS*PEEK (D+N1)
7240 LET X=INT ((B-CL)/R+N1/N2)
7250 IF X<64 AND X>=N0 THEN PLOT X,Y
7260 LET D=D+N2
7270 NEXT Y
7280 LET TM=TM+N1
7290 LET C=C+N1
7300 IF TM=5 THEN LET TM=N0
7310 IF C<>32 THEN GOTO 7340
7320 LET C=N0
7330 LET F=F+N1
7340 NEXT L
7350 IF NOT DR THEN COPY
7360 IF DR THEN PAUSE 4E4
7370 IF L<32*N THEN GOTO 7180
7380 GOTO H5
7900 LET N$="WHICH SCREEN? (01-32)= "
7905 GOSUB 8000
7910 LET FL=A
7915 POKE 16844,FL
7920 POKE 16845,N0
7925 RAND USR 16611
7930 RETURN
7950 LET N$="HOW MANY SCREENS? ( TO "+STR$ (33-FL)+"): "
7960 GOSUB 8000
7970 LET N=A
7980 RETURN
8000 PRINT ,,N$;
8010 LET Z$=INKEY$ 
8020 IF Z$<"0" OR Z$>"9" THEN GOTO 8010
8030 PRINT Z$;
8040 IF INKEY$ <>"" THEN GOTO 8040
8050 LET Y$=INKEY$ 
8060 IF Y$="" THEN GOTO 8050
8070 IF CODE Y$=118 THEN GOTO 8110
8080 PRINT Y$;
8090 IF Y$<"0" OR Z$>"3" OR (Z$="3" AND Y$>"2") OR Y$>"9" THEN GOTO 8160
8100 GOTO 8130
8110 LET Y$=Z$
8120 LET Z$="0"
8130 PRINT " *"
8140 LET A=O0*VAL Z$+VAL Y$
8150 RETURN
8160 CLS
8170 GOTO 8000
8200 RAND C0
8210 FOR F=FL TO FL+N-1
8220 POKE 16854+2*F,PEEK S1
8230 POKE 16855+2*F,PEEK S2
8240 NEXT F
8250 RETURN
8300 LET C0=PEEK (16854+N2*FL)+TFS*PEEK (16855+N2*FL)
8310 LET CM=C1*C0/65535
8320 LET TB=INT (TREF*C0/655.35+.5)/O0/O0
8330 LET SR=N2*H5*TB/64
8340 LET CL=PL*CM
8350 LET CH=PH*CM
8360 RETURN
8400 POKE 16418,N0
8410 SLOW
8420 PRINT AT 23,N0;"[Z]- COPY";TAB 23;"[C]- CONT "
8430 POKE 16418,N2
8440 IF INKEY$ ="Z" THEN COPY
8450 IF INKEY$ ="C" THEN RETURN
8460 GOTO 8440
9970 CLS
9974 PRINT "█[P][U][T]█[R][E][C][O][R][D][E][R]█[I][N]█["][R][E][C][O][R][D]["]█[M][O][D][E]█",,,"██[T][H][E][N]█[P][R][E][S][S]█[A][N][Y]█[K][E][Y]█[T][O]█[S][A][V][E][.]██"
9976 IF INKEY$ <>"" THEN GOTO 9976
9978 IF INKEY$ ="" THEN GOTO 9978
9980 CLS
9982 SAVE "VDAQ[1]"
9984 GOTO H5
9985 SAVE "VDAQ[1]"
9986 RUN 
9990 CLS
9991 POKE BL,0
9992 PRINT AT 21,0;"  GOTO 500 TO RE-START","""ENTER"" TO  LIST "
9993 FAST
9999 POKE 16384,89
```