C.P.U.'s Original SDrive

These are the SDrive's original features, quoted from the original SDrive by C.P.U. page:

• Supported flash cards: SecureDigital up to 2GB size, FAT16 filesystem
• Maximum number of drives: 4 (D1: to D4:) + 1 special boot drive
• Supported SIO transfer rates: 3.5 to 128kb/s (standard 19 and 69kb/s)
• Supported disk images: ATR, XFD, size up to 16MB, 128 or 256B sectors
• Supported executable files: COM, XEX, BIN.... (any filename extension).
• Device controlled by software running on Atari from the SD card, which can be therefore easily updated/replaced
• Drives swappable on the fly by buttons
• Write protect/enable switch
• SDrive ID number selection switch - simultaneous use of up to 4 SDrives
• Low cost design – no LCD, a few LEDs, cheap DIL28 Atmega8 MCU, single sided PCB*
• Firmware and software sourcecode freely available

When C.P.U. released the original SDrive information on their site, it was accompanied by a file SDrive081012.zip containing schematics, firmware, applications, photographs, documentation, and source code related to their project. This open-source information is invaluable, and without it the SDrive NUXX would not have been possible. A mirror of this file can be found here: SDrive081012.zip.

During the final phases of the SDrive NUXX development, C.P.U. released some updates to the SDrive, including different fuse programming recommendations and a new control program for the SDrive. These changes are encompassed in SDrive20090403.zip, which I have mirrored here: SDrive20090403.zip.

It is strongly advised that one review these file, particularly the SDrive_en.pdf documentation which covers the use and operation of the SDrive. All efforts have been made to ensure that the SDrive NUXX's function is identical that of the original SDrive.

SDrive NUXX Changes

The first, and most obvious change from the original SDrive, is the use of a readily available enclosure and custom end panels with cutouts and artwork. These changes imply a different PCB and component layout, which include slightly modified control layout.

The second change with the SDrive NUXX design is the use of an SIO connector footprint. This allows a standard Atari SIO connector to be used, allowing easy connectivity with any of the compatible Atari 8-bit computers.

Third, the new PCB design incorporates a low-cost AVR programmer allowing a SDrive builder who doesn't have AVR programming hardware readily available an easy method of loading the firmware on the microcontroller. Adding this programmer to the board adds only a few dollars to assembly cost, with the vast majority of that being in the DB25 connector.

SDrive NUXX PCBs v1.1

SDrive NUXX PCB v1.1 Export from CadSoft EAGLE

SIO Connector

For easiest connection to an Atari 8-bit computer, the SDrive NUXX PCB has added a footprint allowing one to fit either an original SIO connector to the board or the original (from the SDrive) DB15. This part footprint, or package in EAGLE parlance, was drawn with measurements taken from a JAE D03 (thick, narrow wing) and validated against four other thin, wide wing SIO connector types. A few variants on this package are available in atari_sio_part_for_cadsoft_eagle.zip.

While soldering the SIO connector to the PCB provides sufficient mechanical retention, it may be desirable to screw the connector down. For the thin, flat-wing, more easily molded connectors a 4-40 machine screw / locking nut set (such as McMaster-Carr part numbers 91772A107 and 91831A005) must be used as there is not enough plastic available in the connector for a screw to bite into. When using the JAE D03 SIO connector with thicker plastic wings, some thread-cutting screws for plastic (McMaster-Carr part number 94629A550) should be used to fasten the connector to the PCB.

This SIO connector footprint is placed on the PCB directly in line with the DB15 connector, allowing the builder their choice of SIO or DB15 connector. The SIO to DB15 connection pinning is as found in the original SDrive, which is detailed in Radek Štěrba's SIO D-SUB15M standard Atariklub PV article (Česky, Google Translation to English).

Built-in Programmer Jumpered to SDrive Circuit

Programmer / Header

In the package of files for the original SDrive, schematics are provided for Jerry Meng (BA1FB)'s Simplified AVR ISP Programmer. This simplification of the Atmel STK200 into one connector and four resistors can easily flash many Atmel AVR microcontrollers. To make programming of the ATmega8 microcontroller easier, this programmer has been included on the SDrive NUXX PCB. If one doesn't wish to use the on-board programmer, parts J2, R14-R17, and potentially J3 may be omitted.

To keep the programmer isolated from the SDrive NUXX during normal use of the device, two rows of pin headers are fitted on the PCB. One half is the normal programming header for the ATmega8, and the other is part of the Simplified AVR ISP Programmer. To connect the programmer to the microcontroller, one simply has to fit five standard .100" jumpers across the pins as seen in this photo. The board can then be connected to a PC's parallel port and the microcontroller programmed.

Note that an SD card should not be in the SD slot during programming of the microcontroller.

Revisions

v1.1: Production version. Changes from v1.0 are as follows:

• Added missing traces between pins 2 and 12 and pins 3 and 11 of J2.
• Rearranged Right/Left/Boot labels on SW1-SW3 to match what the switches actually do.
• Fixed (reversed) part outline for IC1.
• Moved SW1-SW4 0.5mm closer to the panel edge to take into account the new, thicker end panel material.
• Made D1 lead spacing wider to match resistors (and facilitate using lead benders).
• Moved IC2 et al to make more room for future development work.
• Optimized numerous routes.
• Resized version / model plate on bottom to match documentation layer.

v1.0: Prototype version, not distributed publicly.

Chassis

Hammond Manufacturing's 1455-series enclosures, the 1455L1201BK was selected as the enclosure for this project. This extruded aluminum enclosure is strong, attractive, available in both black and silver (natural), and reasonably priced. The black version (BK part number suffix) is the standard part used for the SDrive NUXX.

This case ships with rubber feet, self-tapping screws, plastic bezels, and metal end panels. The metal end panels are discarded in place of the custom end panels, but the rest of the mounting hardware is used to hold the SDrive NUXX PCB snugly in the card guides and against the end panels.

SDrive NUXX End Panel Artwork

End Panels

The end panels for the SDrive NUXX are made out of photo sensitive aluminum material known as Metalphoto. This material is then laminated on to a thicker aluminum sheet and drilled / punched to produce the final panels. These custom end panels were designed based on dimensions provided by Hammond Manufacturing in their 1455L1201BK data sheet and are manufactured by [url=http://www.mpofcinci.com/]Metalphoto of Cincinatti[/url].

The original Hammond Manufacturing end panels, provided with the case, are 1.5mm thick. In order to have a sufficiently rigid end panel, ~2mm pieces were selected for the SDrive NUXX. These panels fit into the plastic bezels which ship with the enclosure and fasten down using four self tapping #6 screws. These screws come with the enclosure.

Omron B32-10xx Keycaps

Keycaps

The Omron B3F-3150 tactile switches used in the SDrive NUXX have a number of different keycaps available. In order to fit in the production front panel, the B32-10xx key caps must be used. Typically three black keycaps (Omron B32-1010 / Digi-Key SW451-ND) are used in the front panel and one red keycap (Omron B32-1080 / Digi-Key SW252-ND) are used, although a number of other colors may also be used. This image shows the Light Grey, Black, Yellow, Blue, Red, and White keycaps.

Here is a list of all the Omron B32-10xx keycaps carried by Digi-Key at the time this article was last updated:

• SW451-ND: Black
• SW250-ND: Blue
• SW450-ND: Light Gray
• SW953-ND: Light Green
• SW845-ND: Orange
• SW252-ND: Red
• SW251-ND: White
• SW249-ND: Yellow

PCB

• When soldering the SD card, be careful that there aren't bridges made between any of the pins and the housing.

• Be sure to align all LEDs and the toggle switch straight with the front edge of the PCB. This will ensure that they fit nicely through the holes in the front panel.

• The tactile switches snap into place and set nicely against the PCB. Be careful that they are seated nicely and not pointing up or down, otherwise the keycaps will not fit nicely through the panels.

• Solder the following parts, in this order, using water-soluble flux, before washing the PCB:

1. SD Card Slot
2. DIP Socket (IC2)
3. D1 - Diode (D1)
4. All Resistors
5. J3 - Pin Header
6. Q1 - Crystal
7. All Capacitors
8. IC1 - LDO Voltage Regulator
9. All LEDs
10. SW5 - DIP Switches (If Washable / Taped Part Selected)

• Wash the flux from the PCB with hot water then dry thoroughly. See this article on flux removal for more information.

• Screw the SIO connector in place before soldering. This lets you ensure that the alignment is proper before any soldering is done.

• Solder the remaining parts with no-clean flux:

1. All Tactile Switches
2. SW6 - Toggle Switch
3. J2 - DB25 Connector
4. J1 - SIO or DB15 Connector
5. SW5 - DIP Switches (If non-Washable / Unsealed Part Selected)

First Power Up

• Before the first power up, check for shorts between the 5V and 3.3V rails and GND. If a short is found be certain to correct it before powering up the board. Next power up the board without an SD card or IC2 (ATmega8) fitted and check the 5V and 3.3V rails at the test points TP1-TP3 to be sure they are at proper levels.

• After ensuring that power is correct, power down the board, insert IC2, and, if needed, program it.

• Be sure that the DIP switches are all in the up / open position. This will turn off the SD Lock Override and set the SDrive NUXX to ID0, which is appropriate when only one SDrive is connected.

• Note that if something goes wrong and the smoke is let out of a component during testing, all the smoke must be collected, reassembled, and reinserted before the part will work again. It is often easier to replace the failed component.

Assembly

• Close up by fitting the rear panel, inserting the PCB, fitting the front panel. This avoids inadvertently damaging the front panel and toggle switch on the work surface.

• Ensure that the top panel is in place before fitting screwing in the screws, as they occasionally impede on the channels which the top panel fit into.

• When pressing the front panel down over the LEDs and toggle switch, be sure that everything is lined up before applying any force. If things are off the parts won't align nicely and one risks bending an LED or expensive toggle switch.

• Don't overtighten the case screws. They are self threading and capable of stripping out the channels which they fit into.

ATmega8-16PU Microcontroller

Firmware

The following two files, taken from either the SDrive081012.zip or SDrive20090403.zip packages, are used to program IC2 in the SDrive NUXX:

FLASH: SDrive.hex (MD5: 4469145fa8018e336dbf3431ae82a86e)

EEPROM: SDrive.eep (MD5: 8ee46ccd9d32867a6ccc049f1146e768)

PonyProg 2000 2.0.7c Beta

PonyProg2000

To program IC2 with PonyProg2000 2.0.7c Beta under Windows, perform the following steps:

1. Install and launch PonyProg2000.
2. Run calibration via Setup → Calibration and ensure that calibration runs successfully.
3. In Setup → Interface Setup select Parallel, Avr ISP I/O, LPT1 (or whichever parallel port you are using).
4. Click Probe and ensure that the probe is successful, displaying Test Ok, indicating that the programmer has been found. Click OK twice to return to the main window.
5. Select File → Open Program (FLASH) File... and open the SDrive.hex file.
6. Select File → Open Data (EEPROM) File... and open the SDrive.eep file.
7. Select Command → Write All to write the data to the FLASH and EEPROM portions of IC2.
8. Select Command → Security and Configuration Bits... to display the Security and Configuration bits dialog. As in this image, uncheck all check boxes except for SPIEN (which may be grayed out), BODLEVEL, and BODEN, then click Write.

If all of these steps complete successfully, the ATmega8 (IC2) on your SDrive NUXX is now programmed and ready for use.

WinAVR / avrdude

When using WinAVR / avrdude, the following command line will program the SDrive NUXX properly, presuming the FLASH and EEPROM files are in the local directory and the programmer is connected to the first parallel port:

avrdude -p m8 -c stk200 -U lfuse:w:0x3f:m -U hfuse:w:0xdf:m -U flash:w:SDrive.hex:i -U eeprom:w:SDrive.eep:i

See the avrdude documentation for details of these and other command line options.

Kingston 2GB SD Cards

Schematic

The SDrive NUXX schematic (v1.1) may be obtained from here in PDF format or here as a 300dpi PNG.

PCB Layout

The PCB layout files, consisting of a schematic (.sch) and board file (.brd) were created in CadSoft EAGLE and are available here: sdrive_nuxx_eagle_v1.1.zip (MD5: 56b853336868161a0afc86a572e06661)

Front and Rear Panels

The front and rear panel artwork, as sent for manufacturing, is available here in Adobe Illustrator format. Note that these files may also be opened with Adobe Reader: sdrive_nuxx_panels_1_0.zip (MD5: 70494f8a2ba25321a9569b8658563d7e)

SIO Connector

The CadSoft EAGLE footprint for the SIO connector is available here: atari_sio_part_for_cadsoft_eagle.zip (MD5: 07f05698e09360178f48f7b06ecd2f86)