Emu68 PWM is an AHI driver that plays through the 3.5mm audio jack of
the Raspberry Pi 4 or Pi 3 in a PiStorm (a PiStorm32-lite, or a classic
PiStorm) running Emu68: a further stereo output next to Paula and next
to the HDMI output of emu68hdmi.audio. Ideal as the headphone (cue)
output of a DJ program such as StormDJ, or as a second output for a
second program.
This is a beta version, tested on...
- a Pi 4 in a PiStorm32-lite with Emu68 1.1.0 beta
- a Pi 3 in a classic PiStorm
- a Pi 3 B in a PiStorm32-lite with Emu68 1.0.7 (flype44's 4.8)
Please report problems to hakke@gmx.de, with your Pi model, your Emu68
version and the output of PWMDiag.
Features
--------
- Two AHI modes, 16-bit stereo 48 kHz: normal (12 x 16 ms buffer) and
low latency (3 x 16 ms), for Units 0-3 and the music unit.
- About 11 bits of resolution: fine for headphones and monitoring.
- Soft start and stop: no thump from the jack.
- AHI's output volume (Prefs/AHI "Output volume"), with a smooth ramp,
from -60 dB up to a +12 dB boost for headphones.
- Optional dither for quiet passages, chosen as the unit's Output in
Prefs/AHI.
- DMA paced by the PWM hardware, completion by interrupt: about 62
wake-ups a second, no polling. On the Pi 3 the interrupt comes
through arm-intc.library, included.
- Up to four programs play through the jack at once, mixed by the
driver: a game and a music player, for example.
- AHI's CPU overload protection, as in paula.audio; no holes while
windows are moved.
- A reset guard: the jack stops cleanly before a reboot.
- Installs next to emu68hdmi.audio: different mode IDs (001f0020,
001f0021), different hardware, both can be in Prefs/AHI.
- PWMTest: a test tone through the jack without AHI, for troubleshooting.
- PWMDiag: what the driver did, for problem reports.
- Emu68PWM-Mixer by flype44: meters, oscilloscope, spectrum and
goniometer of the sound leaving the jack (MUI 3.8+).
- An AmigaGuide manual.
Requirements
------------
- A PiStorm with a Raspberry Pi 4 Model B, or a Raspberry Pi 3
Model B, B+ or A+: the models with the 3.5mm jack.
NOT the CM4, CM3, Pi 400 or Pi Zero 2 W: they have no jack, and on
them GPIO 40/41 are wired to other parts of the board. Since 4.10
the driver, PWMTest and PWMDiag refuse them and touch nothing.
- Emu68 with devicetree.resource in its ROM; on the Pi 4 Emu68 1.1
or newer (gic400.library 1.3+).
- On the Pi 3: arm-intc.library 0.3 or newer, recommended (the DMA
interrupt instead of polling). It is in the Libs drawer of this
archive; source: https://github.com/flype44/arm-intc.library
- AHI 6.x.
No mailbox.resource is needed any more: the driver used it only to ask
the firmware which DMA channels are free, a list the device tree holds
already. So 4.9 also runs with Emu68 1.0.7, whose ROM has none, until
Emu68 1.1 is final.
Installation
------------
From the archive:
Copy Emu68PWM/Devs/AHI/emu68pwm.audio DEVS:AHI/
Copy Emu68PWM/Devs/AudioModes/Emu68PWM DEVS:AudioModes/
and on a Pi 3, unless a newer one is installed:
Copy Emu68PWM/Libs/arm-intc.library LIBS:
Reboot and pick an Emu68 PWM mode in Prefs/AHI. See Emu68PWM.guide.
Internet radio
--------------
AmigaAMP plays MP3 streams over HTTP through the jack. On a Pi 3 a
128 kbit/s stream leaves about 85% of the 68k free. Best settings in
AmigaAMP's Prefs: Buffers Loading 64-128 KB, Playback 1/2-1 s; Task
Priorities Playback 5, so that moving windows leaves no holes.
Credits
-------
Many thanks to flype44 for 4.8: the DMA interrupt on the Pi 3, up to
four programs at once, no holes while windows move, the reset guard
and Emu68 1.0.7 support; and to arczi84 for the mixing of several
programs in emu68hdmi.audio 4.18, on which that is based.
Emu68PWM-Mixer by Philippe Carpentier (flype44), GPL-3.0-or-later.
Built on emu68hdmi.audio 4.17 (arczi84, flype44; GPL-3.0-or-later);
several programs at once after emu68hdmi.audio 4.18 (arczi84).
arm-intc.library (flype44, MPL-2.0); the reset guard of emu68-common
(Rondoval, MPL-2.0 or GPL-2.0+).
PWM sound set-up after Circle by R. Stange (GPL-3.0-or-later).
Emu68 and its resources by Michal Schulz, AHI by Martin Blom.
Author: Andreas Winkler - www.taiwanrider.com
(HAKKE Online Shop, Amiga and synthesizer related hardware and software).
License
-------
GNU General Public License, version 3 or later: see COPYING. The complete
source code is in the Source drawer of this archive; please pass the
archive on complete, with it.
Disclaimer
----------
Emu68 PWM is provided "as is", without warranty of any kind. You use it
at your own risk: the author takes no responsibility for any loss of
data or for any damage to software or hardware, whatever the cause.
History
-------
4.10 SAFETY FIX: refuses every board without the audio jack (CM4,
CM3, Pi 400, Zero 2 W). Earlier versions accepted the CM4, the
Pi 400 and the CM3 and drove GPIO 40/41, which are wired to
other parts there (the boot EEPROM's SPI lines on a CM4).
Thanks to flype44 for the warning.
New: Emu68PWM-Mixer by flype44.
4.9 Improvements by flype44 (his test version 4.8):
Pi 3: DMA interrupt through arm-intc.library (included).
Up to four programs at once, mixed.
No more holes while windows are moved.
Reset guard: the jack stops before a reboot.
No mailbox.resource needed: runs with Emu68 1.0.7.
4.7 Sound comes back after an Amiga reset (no Pi restart needed).
4.6 First public release.
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