+DrVenkman Posted July 13, 2018 Share Posted July 13, 2018 So I built an SDrive-MAX Arduino powered device but have a problem when it's wired up as expected, with an 1N4148 diode connected between the Atari DATA IN line and the Arduino TxD pin. I removed the diode and voila, it works again. I asked about this a few days ago in another thread: Cathode (black band) end soldered to the Arduino. Which confirmed what I had done. Anyway, to avoid cluttering up that thread (which is about ATX support being added to the SDrive-MAX firmware), I decided a new thread would be more appropriate, and probably helpful for anyone assembling these going forward. So ... Anyway, I got my 3D-printed case today (huzzah!) and when I went to rewire the device with the diode installed again, I did it this way: (After soldering, of course I trimmed off the excess leg and then covered everything with heat shrink). I then soldered in the leg on the black band-side to the Arduino, and measured the forward bias of the diode (red probe of the multimeter in Pin 3 of the SIO plug, black probe on the pin of the Arduino) and got 0.601 volts, exactly as expected for a silicon diode. Reverse bias was OL measured by reversing the probes, also as expected. I put the device inside the case, booted the computer and … nada. So I took things apart again and soon as I removed the diode, things are working great again. Huh. So variables: the type of Arduino used - a cheapie little clone Uno with additional vias inboard of the headers; power source: Atari SIO +5V pin. Makes no difference whether I plug it in directly to the computer or at the end of the daisy chain; computer used: 1088XEL, normally with an SIO2PC connection to RespeQt through a Sparkfun FTDI-based serial board, two 1050's connected to the SIO port, and a P:R:Connection at the end. I have zero problems using both the SIO2PC device or the floppy drives, simultaneously or separately. They just work. Of course, the XEL is designed for this and the Sparkfun FTDI board has the right isolation already for simultaneous work. So does anyone have ideas why installing the recommended diode is interfering with my other SIO storage devices? I have not tested with another computer, though I'm tempted to this weekend to see if this is a quirk of the 1088XEL. But in happier news, the thing works GREAT. My friend is still dialing in his printer so there are few imperfections but most of those will be easy to take care of this weekend with some very fine sandpaper. I stuck rubber feet on the bottom for stability too, which is highly recommended. 2 Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted July 13, 2018 Share Posted July 13, 2018 (edited) not sure about this but did you try the same thing but on the Atari data out, and arduino data in...rxd it's easy to forget the drives cross over ... I need to see you sio cord pin 3 pin 5 Atari out is 1050 in Atari in is 1050 out all things being equal the same should hold true for the uno... Edited July 13, 2018 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 13, 2018 Author Share Posted July 13, 2018 not sure about this but did you try the same thing but on the Atari data out, and arduino data in...rxd No. I was following the instructions here: http://www.kbrnet.de/projekte/sdrive-max/index.html Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted July 13, 2018 Share Posted July 13, 2018 (edited) the wording 'across' is strange... inline or connected from-to makes sense... across what is the question.. hmmmm sounds like the black ring is connected towards the Atari and all the other drives etc. side of things..... so uno txd anode diode cathode Atari stuff....... verify with all powers off and a DMM that pin 3 in the atari is connected to black ring side of diode and the anode to uno txd.... I think it is indeed saying the cathode identified by the black ring goes to pin 3 of Atari computer SIO Port.... please show us the sio cord with shell (hood) off Edited July 13, 2018 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 13, 2018 Author Share Posted July 13, 2018 the wording 'across' is strange... inline or connected from-to makes sense... across what is the question.. hmmmm sounds like the black ring is connected to the Atari side..... not uno side... so uno txd anode diode cathode Atari....... verify with all off and a DMM that pin 3 in the atari is connected to black ring side of diode before r3 txd.... This is an auto-translation of a page that's in German. The text in the table says the black ring goes to the Arduino TxD pin. And in my initial post, I quite forum member 'remowilliams' who has also built one of these. Quote Link to comment Share on other sites More sharing options...
AtariGeezer Posted July 13, 2018 Share Posted July 13, 2018 How are you powering it? USB wall-wart adapter or connected to a PC? Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 13, 2018 Author Share Posted July 13, 2018 How are you powering it? USB wall-wart adapter or connected to a PC? I’m powering it through the Atari SIO bus. Should that make any difference though? I honestly dunno. The device seems to work fine other than the issue with the diode installed. Without the diode, even powered by the SIO bus, it can load and write files normally, even using high-speed I/O, it can load XEX files, etc. I haven’t tried cassette emulation but it’s on the list. If no one else has any suggestions, I guess at some point this weekend I can disconnect the SIO power line, wire the diode back in and see if powering it from a standard Arduino 9V battery adapter makes a difference. Quote Link to comment Share on other sites More sharing options...
AtariGeezer Posted July 13, 2018 Share Posted July 13, 2018 If it was powered through a USB Port on a PC, the data lines RX and TX might have interfered with IO. But that can't be if powered by SIO port. Just a thought... Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted July 13, 2018 Share Posted July 13, 2018 yes on regular sdrive and sio2sd the cathode ring is towards the device/chip and the andode is to the sio side.... can we see it and the sio cord and it's connector end? Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 13, 2018 Author Share Posted July 13, 2018 (edited) can we see it and the sio cord and it's connector end? See the photo and text in my first post above. And as I said in my first post, I verified the diode forward and reverse bias from the SIO pin (pin 3 on the connector) all the way to the pin on the Arduino (i.e., through the diode). Edited July 13, 2018 by DrVenkman Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted July 13, 2018 Share Posted July 13, 2018 (edited) that is not enough to verify, I want to trace out the colors on the cord and make sure it all lines up. to see what's what it's best to see all connections... I've ordered the same as you to check out what could be the issue.... have you verified what level is being put out to the SIO lines? lastly have you tried with anything other than 1088XEL? Edited July 13, 2018 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 13, 2018 Author Share Posted July 13, 2018 that is not enough to verify, I want to trace out the colors on the cord and make sure it all lines up. to see what's what it's best to see all connections... I've ordered the same as you to check out what could be the issue.... have you verified what level is being put out to the SIO lines? lastly have you tried with anything other than 1088XEL? All of this is in the first post. I've traced out all the pins and connections, multiple times. As I keep repeating, everything works great without the diode. With the diode, it doesn't work at all. Quote Link to comment Share on other sites More sharing options...
BigBen Posted July 13, 2018 Share Posted July 13, 2018 An image with all connections is certainly helpful. Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 13, 2018 Author Share Posted July 13, 2018 An image with all connections is certainly helpful. That's exactly how I had it wired up, except that I didn't wire both ground wires, just one (the diode is under the un-shrunken heatshrink tube), black ring end soldered to the via (orientation shown in the first post of this thread). No sense showing the connector end because it's a vintage cable; the colors were the then defacto "standard" used for many/most vintage SIO cables and before I wired up anything, I spent 15 minutes with a multimeter, pencil and paper and verified continuity from each pin to the correct wires, noting color to be sure. Again, IT WORKS WITHOUT THE DIODE. I'm trying to isolate what's going on. Is it the diode I'm using? It's a 1N4148, forward bias is right on 0.601 volts, reverse bias is OL. Is it because I'm powering it with the Atari SIO line instead of a wall wart or battery? Is it this particular variant of UNO clone? I'm stumped. Quote Link to comment Share on other sites More sharing options...
tomsmart1 Posted July 13, 2018 Share Posted July 13, 2018 (edited) It will work without the diode if its the only device that is connected to the Atari, but you or more audrino get in trouble if xou connected together with other devices like Diskdrives. I suggest to use the SIO2SD modifications with a shotky diode like BAT50, that have only a voltage drop of 0.2V. An a powerup Resistor on the audruio side I will test this in a week because i an now on a vacation trip. Edited July 13, 2018 by tomsmart1 Quote Link to comment Share on other sites More sharing options...
JR> Posted July 13, 2018 Share Posted July 13, 2018 Got mine soldered up today and it worked first time with a 1N914 diode I had laying around. From what I can see of your board in the above picture it appears to be the same board. This is running on SIO power from a 600xl. Thsi is the board I ordered: https://www.amazon.com/gp/product/B01AR7YJ3O/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1 Any chance of buying one of those cases? They look great! 1 Quote Link to comment Share on other sites More sharing options...
NISMOPC Posted July 13, 2018 Share Posted July 13, 2018 Got mine soldered up today and it worked first time with a 1N914 diode I had laying around. From what I can see of your board in the above picture it appears to be the same board. This is running on SIO power from a 600xl. Thsi is the board I ordered: https://www.amazon.com/gp/product/B01AR7YJ3O/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1 Any chance of buying one of those cases? They look great! I was wondering about that! I used the 1N914 for my USB SIO2PC that I made and when I saw this one required the 1N4148, I was slightly confused. My board and screen should be here any day now. I have both diodes, but think I will stick with the 1N914... ...even thought the 1N4148 is supposed to be an improved version of the 1N914 and can be used in place of it?!?! Quote Link to comment Share on other sites More sharing options...
JR> Posted July 13, 2018 Share Posted July 13, 2018 They are basically identical. Just what I happened to have laying around. Quote Link to comment Share on other sites More sharing options...
_The Doctor__ Posted July 13, 2018 Share Posted July 13, 2018 (edited) double check some things- ensure none of the hacked end connections touch anything, not the shield, not each othe, not the ardy, no whiskers etc.... verify that there are no pinched wires in the cord causing continuity/leakage across pairs of them... it couldn't hurt to swap the diode either... even if it tested well. until mine arrive... I would try making connections for power near the power jack etc.. moving to alternate connection points just in case the pcb has a flakey via issue etc... Edited July 13, 2018 by _The Doctor__ Quote Link to comment Share on other sites More sharing options...
xrbrevin Posted July 13, 2018 Share Posted July 13, 2018 have you seen this version of the guide? https://translate.googleusercontent.com/translate_c?act=url&depth=1&hl=en&ie=UTF8&prev=_t&rurl=translate.google.com&sl=de&sp=nmt4&tl=en&u=http://www.abbuc.de/community/forum/viewtopic.php%3Ff%3D15%26t%3D9451&xid=17259,15700021,15700043,15700124,15700149,15700168,15700186,15700190,15700201,15700208&usg=ALkJrhjuVEDmFNUD_0nwU75v29rzDAsftg it also was originally in german but maybe if it has been worded differently, it may translate better or help for cross-referencing? thanks for posting about this device doctor venkman, i never knew about it. i got my arduino uno today and hopefully my touchscreen will arrive tomorrow! 1 Quote Link to comment Share on other sites More sharing options...
AtariGeezer Posted July 13, 2018 Share Posted July 13, 2018 For reference, here are the schematics for the 2 different UNO Boards: 1 Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 13, 2018 Author Share Posted July 13, 2018 For what it's worth, this afternoon I tried reinstalling the diode, removing the +5V line from the Arduino and powering with a 9V battery wart. While testing, I did think to tap the blue "READY" region at the bottom of the screen to see the SIO bus status. So the device is seeing the SIO query from the computer, but nothing else is going on: Of course, once I remove the diode, things are fine again. I've been PM'ing with 'remowilliams' - he's using the same Arduino board I am and not having issues with a diode installed, though his diode's forward bias is in the 0.5V range. I've gotta wonder if my diodes are just out of spec? I'll order some more this week from a different vendor just in case. So aside from this diode-weirdness with my particular unit, I gotta say this is a pretty great little device. It's cheap, easy to build, easy to flash software to, and works very well. 1 Quote Link to comment Share on other sites More sharing options...
xrbrevin Posted July 14, 2018 Share Posted July 14, 2018 is it worth re-flashing the hex files to the uno? Quote Link to comment Share on other sites More sharing options...
+DrVenkman Posted July 14, 2018 Author Share Posted July 14, 2018 is it worth re-flashing the hex files to the uno? I might try that at some point but first, I think I'll wait to see if a diode from an alternate vendor makes a difference (arriving Sunday). I honestly have no idea what's going on here, nor why the board can't transmit through the diode. I might chalk it up to possible damage to a trace on the board from all the rework at that via and pin, except that I had it wired up correctly to begin with and it didn't work. So I'm fairly confident damage to this board is not the root cause here. Quote Link to comment Share on other sites More sharing options...
AtariGeezer Posted July 14, 2018 Share Posted July 14, 2018 My 2 UNO boards will be here in the next hour, I'll build up 2 of these today and test my diodes (914's and 4148's)... Quote Link to comment Share on other sites More sharing options...
Like us on Facebook
Follow us on Twitter
AtariAge on Instagram
Watch us on YouTube
Chat on Discord
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.