MD Remote Resistor Values

Sun, 15 May 2022 12:00:00 +0000

The wired remotes for MD portables use a resistor ladder to detect button presses. Here's a few I measured myself, plus some information on behavior between generations.

Portable MiniDisc recorders from Sony usually have a wired remote control. Button presses are detected based on the resistance between pin 2 and 4.

Pin 1 and 3 are used for the LCD data protocol, some of which is decoded by Ryan "Izzy" Bales and further documented by asivery, but this post here deals with buttons on pin 2 and 4.

Lots of hobby projects in the last two decades have used this simple interface to create PC-based titling and remote control solutions (I even built my own back in the day based on Lionel Pawlowski's MD COM interface, which I called FunkyMD using the PC Parallel Port).

These days, fijam's gmdrec project can do all this over USB with a MCP2221A USB-to-I2C bridge and an AD5245BRJZ50 digi pot, which is quite fancy an easy-to-use, and you can just order the hardware over at Tindie.

The connector has been measured by Maz in the gmdrec project, which includes a PCB file for the physical dimensions: Remote connectors

RM-MC11EL

No dedicated "play" button. Ships with at least MZ-R900 and MZ-R909. Vol+/Vol- is done by pulling out the jog controller (that usually works as play/ffwd and prev/rew when tilted) and tilting it up/down. Left picture shows the lever pulled out, right picture shows it pushed in. The "stop" button is at the end of the remote control (the 3.5mm headphone jack is coming out of the "back" of the remote diagonally).

Button | Ohms
prev/rew | 1002
sound | 2302
play/next/ffwd | 3649
pause | 5163
stop | 7090
vol- | 8390
vol+ | 9890
display | 16690
playmode | 14290
rpt/ent | 11890

RM-MC38EL

Ships with MZ-RH1 and possibly others. Silver and black versions.

Has a dedicated "play/pause" button and group buttons (next group, prev group).

The "group-" button has the same resistor value as the dedicated "pause" button on older units, and the "group+" button has the same resistor value as the dedicated "tmark" button on older units (the "rpt/enter" button on the RM-MC11EL has the same resistor value).

The 3.5mm headphone jack is directly at the end of the remote, aligned with the remote's center axis.

At least on the MZ-N510, with a 100kOhm pull-up resistor on the LCD data line, the device interprets them as group buttons.

Resistor values of buttons not seen on RM-MC11EL:

Button | Ohms
play/pause | 332
group+ | 11920
group- | 5179

gmdrec resistor values

Source: Maz (Discord)

Button | Ohms
Play | ~200
Prev/Back | 1000
Sound | 2300
Next/Fwd | 3650
Pause | 5160
Stop | 7100
Vol- | 8400
Vol+ | 9900
TMark | 11900
Playmode | 14300
Display | 16700
Record | 19500

RM-MZR30MP

Source: Sony MiniDisc® RM-MZR30MP Remote Control Hacked

Function | Ohms
Prev/Back | 1000
Next/Forward | 3627
Pause | 5156
Stop | 7050
Volume - | 8400
Volume + | 9900
Track Mark | 11900

Not present on RM-MZR30MP, but understood by MZ-R30:

Function | Ohms
Mode | 14000
Display | 17000
Record | 19500
Test Mode | 24000

MZ-N510 Behavior

This recorder's behavior differs with the same resistance values when using RM-MC11EL compared to gmdrec + 100kOhm pulldown on the LCD data line.

It is assumed (but not tested) that recorders that are of the same line as the MZ-N510 or newer units behave similarly.

Note: The RM-MC11EL doesn't have a dedicated 200 Ohm "play" button, the 3650 Ohm Play/FFwd "button" (jog "up" movement) is used as both playback and next track toggle.

Ohms | RM-MC11EL | gmdrec + 100kOhm pulldown on LCD data
200 | - | play/pause toggle
3650 | starts playback if stopped/paused, goes to next track otherwise | goes to next track, even in paused/stopped state
5160 | toggles pause only, does not start playback if stopped | navigates to next group