USB support via SD sharing -- didn't work
localroger
Posts: 3,452
In case anybody else gets this idea, I can save you twenty bucks.
Curiosity finally got the better of me so I decided to sacrifice an Ativa SD to USB reader and SanDisk 2Gb SD card to see if I could wire them up in parallel with a Prop, thus allowing me to read the SD via USB after writing cool data to it from the Prop.· The Ativa converter is sold by Office Depot and costs around USD$12.
In order to get access to the SD socket pins, which are not through-hole, I had to cut the top of the SD socket off and break off a bunch of pincher and ground pins that were in the way.· I tack soldered stiff wires to the SD socket pins and got it plugged into my Demoboard breadboard.· This, of course, left me with no SD socket so I had to do the same thing to the SD card.· I got it plugged into the same row of holes, verified that I had no shorts and good connections, and before going any further I decided to hook up to the computer to make sure it still worked.
Alas, while the computer recognizes the adapter, the adapter doesn't recognize the card.· However, it takes significantly longer to fail to recognize the card than an identical adapter that hasn't been mangled and had leads tacked to its socket pins, which suggests to me that at the higher frequencies of the SD interface, all that wire just has too much inductance or capacitance to let it function.· I'd guess that it's finding the card at the relatively low startup frequency, and then tripping over itself when it tries to switch up.· It's probably trying several times before giving up, thus the noticeable delay before it tells me to stick a disk in the drive.
Considering that any practical implementation will need even more wire than this, pullups, and so on, I think it's safe to conclude that it's unworkable.
Curiosity finally got the better of me so I decided to sacrifice an Ativa SD to USB reader and SanDisk 2Gb SD card to see if I could wire them up in parallel with a Prop, thus allowing me to read the SD via USB after writing cool data to it from the Prop.· The Ativa converter is sold by Office Depot and costs around USD$12.
In order to get access to the SD socket pins, which are not through-hole, I had to cut the top of the SD socket off and break off a bunch of pincher and ground pins that were in the way.· I tack soldered stiff wires to the SD socket pins and got it plugged into my Demoboard breadboard.· This, of course, left me with no SD socket so I had to do the same thing to the SD card.· I got it plugged into the same row of holes, verified that I had no shorts and good connections, and before going any further I decided to hook up to the computer to make sure it still worked.
Alas, while the computer recognizes the adapter, the adapter doesn't recognize the card.· However, it takes significantly longer to fail to recognize the card than an identical adapter that hasn't been mangled and had leads tacked to its socket pins, which suggests to me that at the higher frequencies of the SD interface, all that wire just has too much inductance or capacitance to let it function.· I'd guess that it's finding the card at the relatively low startup frequency, and then tripping over itself when it tries to switch up.· It's probably trying several times before giving up, thus the noticeable delay before it tells me to stick a disk in the drive.
Considering that any practical implementation will need even more wire than this, pullups, and so on, I think it's safe to conclude that it's unworkable.
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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm