15 pin D-SUB male connector at the Atari.
The Atari 5200 SuperSystem (1982) uses a proprietary 15-pin D-subminiature (DA-15 style) analog controller port that was a deliberate departure from the 9-pin DE-9 digital joystick interface used on the Atari 400/800 computers. Each port carries two analogue potentiometer axes (X and Y), a 4×3 keypad matrix plus Start, Pause, and Reset buttons, a bottom fire button (Trigger) with a dedicated TRIG line per port, a top fire button (Softfire) routed to POKEY’s KR2 keyboard-read line, and a regulated analogue supply voltage (+CAV) for the potentiometer wipers. The original 4-port console model (CA018087) and later 2-port model (CA021374) both use the same CX52 controller wiring documented in the Atari CX 5200 Field Service Manual, Rev 4 (July 1983).
| Pin | Description |
|---|---|
| 1 | Keypad – right column |
| 2 | Keypad – middle column |
| 3 | Keypad – left column |
| 4 | Start, Pause, and Reset common |
| 5 | Keypad – third row and Reset |
| 6 | Keypad – second row and Pause |
| 7 | Keypad – top row and Start |
| 8 | Keypad – bottom row |
| 9 | Pot common |
| 10 | Horizontal pot (POT0, 2, 4, 6) |
| 11 | Vertical pot (POT1, 3, 5, 7) |
| 12 | 5 volts DC |
| 13 | Bottom side buttons (TRIG0, 1, 2, 3) |
| 14 | Top side buttons |
| 15 | 0 volts – ground |
It’s handy to consider the keypad in a matrix format:
| Pin | 4 | 3 | 2 | 1 |
|---|---|---|---|---|
| 7 | Start | 1 | 2 | 3 |
| 6 | Pause | 4 | 5 | 6 |
| 5 | Reset | 7 | 8 | 9 |
| 8 | - | 0 | 1. |
For instance, pressing button 5 makes a connection between pins 2 and 6.
Notes
The connector on the console side is a 15-pin D-subminiature female (DA-15F); the CX52 controller cable terminates in the matching male plug. Wire colours as documented in the Field Service Manual Figure 6-9: Pin 9 (+CAV) uses a black wire, Pin 10 (X-axis pot) brown, Pin 11 (Y-axis pot) red, Pin 13 (Trigger) yellow, Pin 14 (Softfire) white/green, Pin 1 (ground) orange, and Pin 15 (ground) shares the return path.
The +CAV supply (approximately 4.2–6 V, set by trimmer R132 inside the console) powers the potentiometer wipers. CONSOL bit 2 must be logic-high to enable this supply; clearing it cuts +CAV and causes all POTx registers to read their maximum value of 228 ($E4). CONSOL bits 0–1 multiplex the keypad and Softfire button across up to four controllers; the Trigger (bottom button) and analogue pot lines have dedicated inputs per port.
The analogue stick does not auto-centre; the centre position must be determined in software, typically by averaging minimum and maximum readings between rounds. POKEY’s RC-timing circuit measures the charge time of a capacitor through the joystick potentiometer and reports it as an 8-bit count (0–228). The CX52 stock potentiometers are 500 kΩ linear; the Field Service Manual specifies a minimum resistance no greater than 50 kΩ and a maximum at least 430 kΩ greater than the minimum.
Signals
Analog Direction Inputs
Potentiometer inputs are 0–500 kΩ, linear. Directional inputs are read by an RC delay circuit: the time it takes a capacitor to recharge through the potentiometer determines the reported position.
- +CAV (Pin 9) — regulated voltage supply (~4.2–6 V) to potentiometer wipers; enabled by CONSOL bit 2
- Horizontal pot / POT0,2,4,6 (Pin 10) — X-axis potentiometer output; lower count = left, higher count = right; North=0 Ω between pins 9 and 11, South=500 kΩ between pins 9 and 11
- Vertical pot / POT1,3,5,7 (Pin 11) — Y-axis potentiometer output; lower count = up, higher count = down; West=0 Ω between pins 9 and 10, East=500 kΩ between pins 9 and 10
- Trigger / TRIG0–3 (Pin 13) — bottom fire button; dedicated line per controller port, active-low, equivalent to the fire button on Atari 8-bit computer joysticks
- Softfire / KR2 (Pin 14) — top fire button; wired to POKEY’s KR2 keyboard-read line, generates a break IRQ (IRQST bit 7) when pressed; multiplexed via CONSOL bits 0–1
- Keypad rows (Pins 5–8) — four row-strobe lines for the 4×3 keypad matrix; each press connects a row line to a column line
- Keypad columns / col-strobe (Pins 1–3) — three column lines for digit keys; Pin 4 carries the common for Start, Pause, and Reset
- Ground (Pins 1, 15) — signal and power return; Pin 1 is also shared with the Softfire button side
- 5 V DC (Pin 12) — console logic supply
Keypad KBCODE values (bits 1–4, read from POKEY via CONSOL multiplexing): 1=1111, 2=1110, 3=1101, Start=1100, 4=1011, 5=1010, 6=1001, Pause=1000, 7=0111, 8=0110, 9=0101, Reset=0100, *=0011, 0=0010, #=0001.