The
Halting Problem
, based on the Music Thing Modular
Turing Machine
, has pin headers for connections to expansion modules like the
HP Potentials
and
HP Gates
. One of these headers is marked GATES1 and the other is PULSES1. Normally expansion modules connect to one or the other, but what if you want to switch between both?
The GATES1 header is connected directly to the shift register output pins. As long as a particular shift register entry contains a 1 bit, the corresponding GATES1 level will be high.
The PULSES1 header connects to logical ANDs of the shift register outputs with the clock. On each clock tick the clock is high, then low. So the PULSES1 levels are high only at the beginning of each clock pulse.
Then if one particular shift register bit is 1 for, say, three consecutive clock pulses, then off, the corresponding GATES1 level will be high continuously for three pulses, then low, while the PULSES1 level will be high, low, high, low, high, low, low, low.
Pulses and gates
The two headers serve different needs. The HP Potentials expander is designed to use the GATES1 header. The gates are scaled and summed to produce a sequence of control voltages; if the PULSES1 header were used the result would be a sequence of short control voltages interspersed with 0 volts, which probably isn’t very useful.
The Music Thing Pulses expander, as the name suggests, was conceived as being connected to the PULSES1 header. Individual bits are broken out to separate outputs as trigger sequences, and some are combined with a logic chip for additional outputs. But in this case there’s no reason the GATES1 header couldn’t equally well be used to make gate sequences, as reflected in the name of my version of the module, HP Gates.
The Music Thing
Vactrol Mix
expander is designed to use the GATES1 header. The Worng
TM-LPG-X
expander is based on the Vactrol Mix, but reworks it as a set of low pass gates instead of vactrol attenuators, and the PULSES1 header is more suitable for it. LMNC Discourse user Clarionet built a
module
that combines the Vactrol Mix and TMLPGX functionality. To facilitate use of both headers they designed a daughterboard that connects to both, and to a toggle switch. The toggle controls three multiplexer chips that switch between the two headers and send the result to the main expander board. There also is a gate input jack which allows switching under gate control.
As the above discussion suggests, such a switch could also be useful for HP Gates.
I did a version of Clarionet’s daughterboard — it’s more or less the same except that I rearranged the components a bit and added a Molex header instead of solder pads for the toggle switch and gate jack. The HP Gates PCB doesn’t have room to add a board mounted jack; I suppose I could have used an open panel mount jack, but I opted to leave the jack out entirely and just add the toggle switch. I could have drilled a hole in the existing panel for the switch, but decided to get a new panel fabbed with the hole drilled and labeled. I built the daughterboard, omitting a few components that are associated with the unused gate jack, and installed it on the HP Gates PCB.
Daughterboard
HP Gates panel with toggle switch
HP Gates PCB with daughterboard mounted
And it all works fine. The two things to watch out for are cable orientation — there are no shrouded headers here, and on the daughterboard, pin 1 is down while on the Halting Problem pin 1 is up! — and toggle switch orientation: You want the connected terminal up to get the functionality to match the panel labels.
My daughterboard repository is here: https://gitlab.com/rsholmes/gates-pulses-switch .