UEF

Contains Python 3 scripts to assist working with UEF files, which are tape images of 8-bit Acorn microcomputers:

• uef2wave
• wave2uef
• bin2uef

All scripts require Python 3. I tested them on macOS X and Python 3.7.0.

uef2wave

Convert UEF files to audible .wav files. With the appropriate cable you can play these back on your Mac or PC and load them via the cassette interface on your Acorn.

You can read the UEF specification one.

There is a --stretch command-line parameter by which you can stretch the duration of carrier tones. The specification states that a carrier tone is one fast cycle, repeated the number of cycles as specified in the UEF file.

However, for some software this seems to be too short, and you can stretch the number of cycles by this factor. For instance, --stretch 2 makes every carrier tone last for twice as long as specified in the UEF.

Supported chunks

The following UEF chunks are supported:

Chunk	Description
0100	Implicit start/stop bit tape data block.
0104	Defined tape format data block.
0110	Carrier tone.
0111	Carrier tone with dummy byte.
0112	Integer gap.
0113	Change of base frequency.
0114	Security cycles.
0116	Floating point gap.

Usage

The script reads the UEF file contents from standard input, and writes the generated .wav to standard output. For example:

$ python3 uef2wave.py < Elite_E.zip > Elite_E.wav

Two remarks:

• Since UEF files are often gzipped, and Stairway To Hell carries .zip files containing gzipped .uef files, you can pass along any of such files. In case of a .zip file, the first .uef inside is processed.
• The generated .wav file is always mono, sampled at 44,100 Hz and 16 bits.

Shoutout

For far more convenience, check out PlayUEF, which allows you to play back audio recordings of various games using nothing but your browser.

wave2uef

Basically the inverse of uef2wave: takes a 16-bit 44 kHz mono .wav file and outputs a UEF file. A bit more limited in the chunks it supports.

Supported chunks

The following UEF chunks are supported:

Chunk	Description
0100	Implicit start/stop bit tape data block.
0110	Carrier tone.
0116	Floating point gap.

Usage

The script reads the .wav file contents from standard input, and writes the generated UEF file to standard output. Prints some debug information to standard error at the moment. For example:

$ python3 wave2uef.py < PERSIAN.wav > PERSIAN.uef
<Gap 1.2 secs>
<Carrier 7.7 secs>
<Data 284 bytes "*PERSIAN">
<Carrier 5.3 secs>
<Gap 2.2 secs>

bin2uef

This is a simple script to store a binary file onto a UEF file, which you may subsequently load into your Acorn micro using uef2wave.

Usage

$ python3 bin2uef.py --help
usage: bin2uef.py [-h] [-n NAME] -l ADDRESS [-e ADDRESS]

optional arguments:
  -h, --help            show this help message and exit
  -n NAME, --name NAME  name to record on tape (default: FILE)
  -l ADDRESS, --load ADDRESS
                        load address (prepend 0x for hex)
  -e ADDRESS, --exec ADDRESS
                        execution address (prepend 0x for hex)

The script reads the file contents from standard input and writes the UEF file to standard output. This way you can easily chain it with uef2wave, should you wish.

Example

Using the xa65 6502 assembler, you can write some machine code and have it execute on your Acorn micro as follows.

Save the following file as hello.asm:

  oswrch = $ffee

  * = $2000

  ldx #0
loop: 
  lda message,x
  beq done
  jsr oswrch
  inx
  jmp loop
  
done:
  rts

message:
  .asc "Hello, world!"
  .byte 0

Then execute the following from a command-line, specifying a name to appear on the tape (-n), as well as the correct load address (-l):

$ xa hello.asm -o - | python bin2uef.py -n HELLO -l 0x2000 | python uef2wav.py > hello.wav

On your Acorn micro, load the hello.wav file, which you play back through the line out of your Mac or PC, and run it:

> *LOAD "HELLO"
Searching

Loading

HELLO      00 001D

> CALL &2000
Hello, world!