DECA Retro Cape 2

(2 layer - MiSTer module SDRAM version)

DECA Retro Cape 2 is an addon for the DECA FPGA development kit from Arrow/Terasic. The addon is connected to the Beaglebone Black connectors and hence the name of Cape as addons in the Beaglebone world are known.

This cape adds IO interface to the DECA board with all is needed to implement retro computers in this beautiful FPGA. Main IO interfaces are DB15 for VGA, PS2 for keyboard and mouse, DB9 for joystick, MiSTer memory connector, MiSTer user port.

Project has been developed with KiCAD 6.0.

Status

STATUS (29/01/23): Tests of v0.90 PCB work as expected, except for JP8 jumper (see testing notes).

STATUS (26/12/22): Finalized design v0.90 and production files including BOM and CPL. See end of readme for changelog improvements from v0.71.

STATUS (07/04/22): PCBs v0.71 received. Started testing. Do not use without modifying voltage protections. Keyboard and Joystick (DB9 and USB3) protections must be redesigned in the next release.

STATUS (15/03/22): prototype desing work finished. v0.71 gerbers sent to JLCPCB for manufacturing.

Credits

I want to give credits to Tom Verbeure from whom I've taken his original design files and adapted to my own design. Not much have been left from his design, but the name "DECA Retro Cape" remains.

Thanks to rest of Hard Team DECA (C.Palmero & Rhoderik) and Telegram groups for the support received during the development phase.

Schematic

arrow_deca_retro_cape.pdf

Features

• VGA DAC 444

  • Jumper to make use of VGA to SCART cables for 15 kHz RGB video

• Terasic 2x20 pin connector (for Mister SDRAM modules) + 3 pin for Dual SDRAM/SRAM

• PS2 keyboard & mouse connectors

• Double Pmod (1/2) for peripherals (VGA Pmod, Hyperram, ...).

  • Added four central pins for compatibility with RGB module of MuseLabs

• Pmod 3 (SPI + UART). Can act as Pmod host or peripheral

• DETO Pmod (6 pin) for general usage (3 multiplexed pins)

• Game controller port (selection jumper to enable one or the other)

  • DB9 connector for joystick (Sega megadrive) (solder JP3 for A.Villena MiSTer DB9 addons)
  • USB3 User Port (for SNAC adapters SNES, Atari, ...)

• UART (Rx/Tx) header

• Power supply headers (5V, 3V3, 3V3 LDO, 2V5 LDO, 1V8 analog)

Important Usage notes

• Better do not connect/disconnect interfaces while the board is powered
• Do not connect two devices simultaneously into DB9 and USB3. Doing so may lead to unpredictabily results and damage the FPGA board
• Prior to first power on it is required to solder jumpers JP2 (pins 3V3 and V) and JP7 (pin 5V and central pin). Read jumper selection notes below
• To use MiSTer memory modules place jumper JP6 to power supply 3V3 (and better left JP5 without jumper)
• Place jumper JP8 on desired interface (DB9 or USB3) for joystick usage. For USB3 jumper JP9 default is I/O.
• For USB3 SNAC adapters do not use the SNAC level shifter adapter as voltage protection is already included in the cape.
• For the rest of jumpers read jumper selection notes below. In case of doubt leave the default recommended position.
• There are a few signals with shared functions that cannot be used at the same time. Those signals are indicated in the PCB silkscreen with ( ) or *, **:
  • (1), (2) are shared between DETO PMOD and PMOD2
  • (3) is shared between DETO PMOD and the MUX signal of DB9 when JP3 is soldered
  • "**" only either DB9 or USB3 connector can be used at the same time (select it by jumper JP8)
  • "*" signals MISO, MOSI, CS2, SCK are shared between PMOD3 and the four pins of J2 and J3 located between pmods 2 & 3

Jumper Selection

Defaults are OPEN (jumper not placed or not soldered) and CLOSED (jumper placed or soldered)

• JP1 jumper select Pmod 3 mode as peripheral (no jumper) or host (with jumper) [default is open]

• JP2 solder jumper selects 3V3 power supply from Deca board or from an optional LDO [default 3V3]. An optional 5V to 3V3 LDO can be soldered if the board cannot cope with the connected loads.

• JP3 solder jumper enables compatibility with Antonio Villena's MiSTer DB9 addons if soldered (MUX signal to allow two joysticks). Be careful, THIS OPTION IS UNTESTED [default open]

• JP4 jumper closed enables 5V at VGA pin 9 to make use of VGA to SCART cables for 15 kHz RGB video [default open]

• JP5 jumper closed power supply 2x20 Terasic connector with +5V [default open]

• JP6 jumper closed power supply 2x20 Terasic connector with +3V3 [default closed]

• JP7 solder jumper to select joystick power supply (5V or 2V5) [default 5V]

• JP8 jumper select either DB9 interface or USER IO (USB3). Only one device can be connected at a time, otherwise might be damaged the FPGA board

• JP9 jumper select USER IO pin 9 function (signal I/O or 3V3 power) [default I/O]

3D model

Changelog

v0.5 routed finalized

v0.6 MiSTer SDRAM only version. Changed to 2 layer board.

v0.62 all finished except VGA R2R schematic and routing

v0.65 power header changed, minor aesthetic changes

v0.68 added vga schematic and indiv. R 0805 into layout

v0.70 routing finished including vga

v0.71 finished prototype desing. Gerber sent to JLCPCB for manufacturing

v0.72 updated pinout spreadsheet and Readme with testing notes and improvements to be done

v0.75 Improvements from testing phase.

• Changed footprint DB15 VGA to fit connectors from Aliexpress (was needed to bend pins)

• DETO Pmod connector change to socket type instead of pin type

• Silkscreen improvements: OSHW logo top

• Removed JTAG footprint

• Change limiting resistor of 180 Ohm to 510 Ohm (ps2 and db9)

• Power header reduced to 1 row instead of 2

• Optimized some traces

• Added solder pad JP3 to enable/disable compatibility with Antonio Villena's MiSTer DB9 addons

• JP4 jumper to enable 5V at VGA pin 9 to make use of VGA to SCART cables for 15 kHz RGB video

• Added PCB Hole for seeing Conf_done, Rx, Tx leds

v0.76 Double pmod 1&2 now compatible with pmod RGB module of MuseLabs (added 4 shared pins)

v0.77 Changes:

• Terasic connector: add jumpers on 5V and 3V3 to disconnect power, so I can connect it to other Terasic powered connectors.
• Replaced 3 pin jumper JP2 with solder jumper on 3V3 power selection
• Added solder jumper to select joystick power supply (5V or 2V5 from LDO)

v0.78 Changes:

• PS2 protection usign 3V9 Zener diodes (3V7 to 4V1).

• Added pulldown optional resistors for ps2 mouse

v0.80 Added Joystick shifter level protection with IC TXS0108E and jumper JP8 to select either DB9 or USB3 IO interface

v0.81 Improved Readme. Added readme notice in silkscreen. Removed v0.78 pulldown optional resistors for ps2 mouse (one of the pins has a physical pull-up resistor in fpga, so wouldn't work).

v0.82 generated BOM before installing jlcpcb-tools plugin

v0.83 Added jlcpcb parts with jlcpcb tools plugin

v0.84 updated USB3 footprint

v0.85 updated references folder. choose zener 3V9 reference

v0.86 updated datasheets, added R7 1Ω for increasing ESR on 2V5 LDO output with a ceramic capacitor instead of tantalum, updated BOM and nearly finished jlcpcb parts selection

v0.87 updated readme. Minor changes on schematic and PCB

v0.90 Finalized design v0.90 and production files including BOM and CPL

TODO improvements

• Reduce lenght of board in VGA wing side
• PS2: Jumpers to activate pull-down resistors to enable USB mode
• If space is needed, make a common ps2 connector for keyb and mouse (ps2 splitter should be used).
• Jumper on joystick DB9 pin 5 to change power supply to pin 7 in order to allow other joysticks like the Amiga one to work. Comment from telegram: "El Jumper lo puedes poner para cambiar la alimentación entre pin 5 y 7. De esa forma te funcionara ok los dos y podrás conectar cosas como el ratón de amiga. De los joysticks clásicos, la mayoría son totalmente pasivos y los quickshot II utilizan la alimentación de 5v para el autofire."
• SDRAM DQ14 and DQ15 position in newer MiSTer modules (xsds) are exchanged respect the older module (xs) I based my design from. This does not affect functionality at all as data in and data out are always in the same order.

Testing

Testings on v0.71 PCB

Testings on v0.90 PCB