As you might know, Garmin datacards contain simply one or two NAND flash chips inside a simple plastic case. Most of the 8, 16, 32 and 64MB cards are populated with only one out of two chips. There have been successful attempts to upgrade those original cartridges with the other chip. This is mostly due to the fact that the datacards are hugely overpriced - usually in the range of three to four times the equivalent Compact Flash memory (using exactly same flash chips plus controller).
Since the Garmin datacard is simply a packaged chip, I have decided to build one myself. My first attempt was based on the Compact Flash and failed miserably. Having spent 5 hours trying to solder wires to TSOP flash chip and fighting with solder bridges I finally gave up.
However it turned out that SmartMedia is in fact a single NAND flash chip wrapped in a nice plastic package. Old PCMCIA card is exactly what is needed to make a 20-pin connector. I have spent £9.99 and about 3 hours putting it all together and here is the result: 32MB DIY Garmin Datacard (shown next to the original 16MB datacard):
Connector is glued to the card with epoxy resin. -SE signal is not needed unlike suggested elsewhere. In fact most of the modern flash chips simply don't have one! If cut to the right size (with scissors), the DIY card fits into the GPS perfectly. It does not have a key to prevent reversed insertion but this can be remedied!
Garmin uses pull-up and pull-down resistors on a few pins but I have used only one 10k pull-up - on R/-B output pin as it is a recommendation of the datasheet. You can see it on the photograph above. The only other SMD component is power bypass capacitor (any will do).
IMPORTANT! Not all SmartMedia cards are the same. This project requires the one that has a chip located underneath (or should I say at the back / on the reverse side) of the gold-plated contacts. If you turn over the card and look at its back you will notice either a "hump", contour or visible patch that reveals the location of the chip. I have had a look at Impact 128Mb SmartMedia card and it has a chip in the middle of the card itself which will not allow cutting it to the size that will fit Garmin standard. Picture below shows detached central part of SmartMedia card with outer border removed.
"Wrong" type of card:
Notice that B in ...SSB0 identifies that the card contains bad blocks.
Below is the picture of "proper" SmartMedia card, e.g. from
Maxell. Note the diffrences:
1. Write protect area (circle to the right of ID) is molded, not painted.
2. Space between gold-plated contact pads are filled with white colour filler. "Wrong" card above has pads directly attached to the black plastic.
3. You can see the chip area on the reverse of the pads area.
Proper type SmartMedia card:
256Mb cartridge from two 128Mb SmartMedia cards. Current Garmin firmware supports only flash chips with a maximum of 128Mb (Device ID 79H). Since the interface has two independent chip select signals, the maximum theoretical limit of the Garmin cartridge is 256Mb. This can be built by stacking two SmartMedia cards around the connector. Let's see how it goes...
Proper formatting of the cards to avoid bad blocks. Garmin uses non-standard bad block table that needs proper initialisation.
External converter for xD-Picture card (which is just a modern reincarnation of SmartMedia).