 Greetings retro friends. This is a Remex punch tape reader. Specifically it's an RRS 7155. So the idea is that you would have some punch tape and if you'll recall last episode I actually punched some tape and it would just go through this thing down here and it would read all the holes and it would output on a DB25 pin connector. Now I also happened to find on eBay the manual for this. Unfortunately this was a photocopy of the original manual so any of the nice grayscale images are unfortunately all washed out but it does come complete with schematics, full-size schematics, which was actually surprising for a photocopy. So this will be able to tell us how it works and you know if something doesn't work I'll hopefully be able to fix it. Now the idea here is here I have a roll of punch tape that I bought on eBay. I have no idea what's on it. There is a label on it that says LBR5 or possibly 6.2 and also T equals 121.11 degrees Kelvin. I guess that means that this is maybe some lab measurements taken at that temperature or maybe a simulation or something. Anyway it would also be nice to just read this and see what's on it. Anyway so the idea is that this would have actually been placed on a spool like this and the take-up reel is over here so the tape would go down here around here up through this reader down here over here and then around into the take-up reel and these are tension arms which presumably work exactly the same way as the perforator did where it can adjust the spooling for proper timing. Now the interesting thing is is that if we take a look inside the machine, let's show you that, here are some parts. Here's a transformer, here are some bulk capacitors for the power supply, this here is a bridge rectifier, so this is you know just your ordinary AC power supply. So the interesting thing is this is one of the spooler motors and this is a potentiometer so as I move the tension arm you can see that the potentiometer actually moves and this is not what we saw on the perforator which was just a simple switch and we'll just turn the motor on and off. The motor actually rotates at different speeds depending on the tension. Same thing here on the other side, here is the motor for the supply reel and this is its tension potentiometer. So that's kind of interesting, it'll be interesting to see how that works. We've got some buttons on the front, the usual on-off button. We have what appears to be a backwards and forwards button and also a loop load spool. This is the logic card back here. There are a whole bunch of potentiometers over here which adjust things like timings and thresholds and if we take a look at the back there's not a whole lot back here. This is where the AC comes in and this is the 25 pin connector that the data will come out on. In addition to this I also received in the package some extra light bulbs and the light bulbs come into play over here and they basically just shine the light through the holes and there are detectors in here and those potentiometers which we saw over here presumably set the thresholds for the light. So when a hole comes in the light goes through, the detector goes off. When there's no hole light doesn't go through and of course for paper tape like this the interesting thing is well how do you set the threshold because you know if it's a very bright light it's going to set off the detector even through the paper. Something like this Mylar tape of course won't have any light going through it at all if there's no hole. So what I thought was we would just start by plugging it in and seeing what happens. Okay so what I've done is I've loaded up the former feed reel or whatever you call it and put it in the take up position I guess. Maybe it's the take up I don't know which way this thing is supposed to go or which way this thing is supposed to read. So what I'm going to try to do is spool the tape and see what happens. So let me turn it off plug the power in make sure that I've got my 25 pin connector connected which I do and now I'll turn it on okay and now I'm going to put it in the spool position and see what happens. So as you can see it sort of loaded itself up now if I move the arrows we can see that we can actually move the tape around. Okay so clearly something is going on here where the motor is actually not able to keep up with the feed rate on here. Let's do the opposite now. Okay that seems to be okay so there's some adjustment that I need to do because it's not able to move this motor as fast and in the other direction yeah everything's just fine. Okay so the next thing that I should be able to do is do exactly that except through the db25 connector the 25 pin connector. So let's see let's drive right which is pin 16. Okay and that actually seems to be slower which makes sense because the manual says that it will go at a certain speed but then when you hit the buttons it'll go faster. So let's go the other direction which is drive left 17. Yeah and that all seems to work. Now one thing that I should point out is that the only thing that's driving the tape is the sprocket motor right. So if the sprocket motor moves the tape this way this tension arm is going to be pulled this way and this tension arm is going to be released this way and that causes these motors to spin to move these tension arms back to their neutral position. So really it's only this motor that's that's kind of controlling the whole thing. So the next thing that we need to do aside from you know make a note that we should take a look at the the voltages over here and maybe adjust that the next thing that we need to do is take a look at the outputs and see what sort of data we're getting. So I'll just maybe hook up an oscilloscope and make sure that we're getting some signals. Okay here we go. Yep all right so we're obviously seeing data and I'll run it the other direction now. Okay so clearly we're seeing some good data. So let's set up the Raspberry Pi to drive this and read some data. Now the way it works is this there is a data ready signal so data ready and the data ready signal basically means that the tape is stopped on a character. So when the data ready signal goes high then we can actually start reading whatever the data is right over here. Now we also have the drive signal and the drive signal is an active low signal. So let's suppose we're driving it and all of a sudden the data ready line goes high well at that point we can stop driving the tape and then we can read the data. So let's say we're going to read the data right here and then after we read the data we can drive the thing again. Now as we drive it as we drive the tape the data ready will eventually when the holes leave the the area of the light the data ready signal will go low and we're going to continue to drive it until the data ready signal goes high again at which point we are going to stop driving the tape read the data and let the tape go again and we let the tape go and then eventually the holes leave the reading area the holes enter the reading area so the data is ready and we stop the tape again and read the data. So that's basically what we're going to do and the other thing is there is a minimum here or actually I guess the minimum would be this and there's also probably a minimum drive pulse as well and I think the minimum drive pulse is something like 500 microseconds and the minimum between the data ready and driving I think is 0.5 microseconds so that's really small but this is a more important number because it basically means you can't drive this really at more than a certain amount in this case I guess it would be well 2,000 characters per second but it turns out that the tape is capable of being driven at a maximum of 400 characters per second and if you drive it like this the capability is actually only 200 characters per second which basically corresponds to a delay so it's 0.005 seconds or five milliseconds per character and that equals 200 characters per second okay so that's what we're going to do and that's the program that I wrote so as before I have the cable going down here this is a cat five cable and it goes up to the raspberry pi now here's the breakout board and you can see that I've got the wires going to a breadboard and if we look at the breadboard we can see some resistors those are 10k resistors and they go directly to the inputs of the raspberry pi and the reason that I did that is that the raspberry pi's inputs are not five volt tolerant and yet we're outputting five volt signals so the resistors basically limit the current that goes to the raspberry pi so that even though I'm sending it five volts the raspberry pi will only that the resistors will drop enough voltage to drop that below 3.3 volts so let's go ahead and run the program and I have the program set up to read 256 characters now you can see that on the leader part of the tape all we're going to be reading is ff's so if I were writing a program to read the entire tape I could just say okay read ff's and throw them away until you find the first non ff character so let's go ahead and read 256 characters and this is going at not not the full speed it's going at I think about 160 characters per second so let's see what happens ah okay so that little click that you heard sort of says I think that something didn't work somewhere along the way and I wonder what it could be okay so I turned the machine off and advanced the tape a little bit and I think I know what's going on if I can zoom in on the tape we can see that there's this double punched area and apparently that caused the thing to malfunction for some reason so now that I'm past that I think that I can start the program up again okay so we've read 256 characters so let's see what those characters are okay and these are the characters so the ff's that you see in the beginning are actually the the leader and then after that it looks like we see a but now this is hex so it kind of looks like we see a bunch of ascii numerals so for example immediately after the leader we get an ad character and then a 0001 01 and then an ac and an ab and then a 000385 and then another ac and an ab and so on and you know there are some other characters in there again I have no idea what this means ac and ab are not anything that I recognize there's also some ad a characters in there but the interesting thing is the the ascii numbers so apparently these are you know maybe some some numeric records but there's nothing else that's interesting in here we can read some more data and see what we get just more of the same yeah and that's just still more of the same just numbers followed by record separator characters and then more numbers the numbers appear to be six digit numbers I guess we could just continue reading to the end of the tape let me just modify the program to read a few more characters than 256 let's read say I don't know 1024 okay and it looks like we're almost at the end of the tape so let's just read some more data okay how much tape have we got we've still got probably about another k of data I think there's probably about 15 or 20 k of data on this tape and that was it so that's what happens when you run out of tape we read the end which was another leader which is a bunch of fs but yeah it it basically seemed to end on the the end of a record the interesting thing is remember I said that there were ac ab's let me show you the screen so here we are at the end of the tape and you can see that we read the I guess you could call it a trailer which is a bunch of ff's and you can see that there are these six digit records it looks like they're basically ASCII zero followed by the record separator acab and then we get a final six zero characters and then the very last character is a b8 maybe that means end of data and then we just get ff's which is the the trailer so that was about it all told there was probably about maybe 15 or 20 k on that tape well I suppose that's it for this fun punch tape exercise so we've been able to punch tape using a perforator and read tape using a tape reader and we read a tape that I got off of ebay and it did not seem to contain anything very interesting it was apparently a data tape and it had it didn't have any actual executable code on it which would have been maybe a little more interesting because then we could actually look at the data and see perhaps what kind of processor it was for but alas this is all I got well I will actually start looking for other tapes on on ebay and you know see if we can find some more interesting data about that but until then I will see you bye bye