[0:00] it actually works that’s
[0:04] amazing so I got a small problem this is
[0:08] my ESP 320x Spectrum board with its um
[0:11] touch Matrix keyboard so it’s using 13
[0:13] touch pins and we’re multiplexing those
[0:16] across the keyboard and it works really
[0:18] well um so I can give you a quick demo
[0:19] here so we go into basic can do 10 print
[0:23] and here we hit a problem so if I try
[0:25] and do symbol shift and P to get the
[0:27] double quote marks you can see we got a
[0:29] weird combination
[0:30] characters we can’t do combined buttons
[0:33] so delete kind of works because it’s on
[0:35] different characters if we try and go
[0:37] into extended mode then we can’t do that
[0:39] either we get all sorts of weird
[0:41] characters coming out it’s basically it
[0:43] works as long as you only do individual
[0:45] characters now I can work around this by
[0:48] using sticky keys so I can make it so
[0:50] that symbol shift sticks on and then you
[0:52] can do p to get quote marks but it’s not
[0:54] ideal I need a bit of a solution so
[0:56] let’s do some experiments
[1:01] so just how does this touch stuff work
[1:02] anyway well what I’ve done is I’ve
[1:04] hooked up a touch pin to my oscilloscope
[1:07] it’s extremely sensitive so I just need
[1:08] to move close to the touch pin and it
[1:10] lights up uh we just wide up to the RGB
[1:12] LED here and if we look at the trace on
[1:14] the oscilloscope when I’m moving close
[1:17] you can see it seems to expand slightly
[1:19] so this regularly repeated pattern is
[1:21] what the esp32 is sending out over the
[1:23] touch pin and it’s basically if we zoom
[1:25] in we can see it’s just a sore too now
[1:30] when I move close to the pin you can see
[1:32] how that expands out so what the esp32
[1:34] does is it times how long it takes for
[1:37] the pad to charge up and down between
[1:39] two certain voltages and it uses that to
[1:41] determine if something’s touching it
[1:43] because the capacitance changes based on
[1:45] is somewhere near or far away so when
[1:48] we’re close there’s more capacitance so
[1:50] it takes longer to charge up and down
[1:52] and when we’re not touching the
[1:53] capacitance goes down and it takes the
[1:55] same amount of time to charge and
[1:56] discharge so it’s really just an analog
[1:58] signal so what I was thinking is I found
[2:01] these nice ic’s they’ve been around for
[2:04] absolutely ever so they’re cheap as
[2:06] chips and there’s multiple manufacturers
[2:08] who make them so what we should be able
[2:10] to do is Multiplex our touch pins now we
[2:13] can Multiplex one pin out to eight touch
[2:16] pins so if I’ve got five of these chips
[2:19] that will give me 40 touch pads which
[2:21] would be one touch pad for each IND
[2:23] individual key of the spectrum keyboard
[2:25] now the only thing is there is an on
[2:27] resistance of this multiplexer so what
[2:29] want to check is does the touch still
[2:31] work when you run it through a resistor
[2:34] so what I’ll do is I’ll just stick my
[2:37] touch pin in there and I’ve got a 270
[2:39] Ohm resistor so let’s stick that in
[2:43] there now let’s see if I touch it it
[2:47] still works so that’s pretty promising
[2:49] so these multiplexor ic’s might be the
[2:51] solution to my
[2:55] problem so I’ve ordered a bunch of these
[2:58] um ic’s and I’ve w add one up so what
[3:01] I’ve got here is I’ve got eight normal
[3:04] GPI op pins just drive some LEDs to
[3:07] indicate if something’s been touched
[3:09] I’ve got this one touch pin going into a
[3:11] multiplexer and I’ve got three address
[3:13] lines so in theory if this works
[3:16] touching these little pads should
[3:19] indicate a touch and it actually works
[3:23] that’s amazing so I can touch multiple
[3:26] pads and I can detect them individually
[3:29] so that’s working amazingly well so I’ve
[3:33] got just one touchpad multiplexing out
[3:36] to eight different inputs so 1 2 3 4 5 6
[3:39] seven seven eight and I can touch them
[3:42] all at the same time and I can detect it
[3:44] and I can detect them individually so
[3:47] this should solve my Spectrum keyboard
[3:50] issue so it’s time to jump into key Cad
[3:52] and get this designed up cuz I think
[3:55] this is going to work amazingly well I’m
[3:58] really pleased that that’s incredible
[4:01] but first time amazing one eternity
[4:05] later so I’m not going to force you to
[4:06] watch a whole bunch of keycard messing
[4:09] around but um here’s our new ic’s so we
[4:12] got one two three four five Multiplex of
[4:15] ic’s so each of these take one touch pin
[4:17] so we have five touch pins and each
[4:19] touch pin is being multiplexed out to
[4:21] eight touch pads so we have 5times 8
[4:23] which is our 40 Spectrum keys so here’s
[4:26] all the keys here we individual bits
[4:28] going to the the um
[4:30] multiplexes uh if we look on the PCB
[4:34] this uh was quite a pain to root but I
[4:36] did manage to root it on two um two
[4:39] layers so that’s pretty good for for a
[4:40] while I was um switching to four layers
[4:42] thinking I’d need to do that but I
[4:44] managed to root it on just two layers
[4:46] and is it rooting or routing routing
[4:48] rooting let me know in the comments
[4:50] rooting or routing which is it when it
[4:51] comes to pcbs so here’s our five ic’s
[4:54] that do the multiplexing there’s a few
[4:56] other changes on the board so there’s
[4:57] new SD card um socket this one’s a lot
[5:00] cheaper than the one I was using so
[5:01] we’ve saved a bit of bomb costs um some
[5:04] new buttons these are now side buttons
[5:06] rather than top buttons got an onoff
[5:09] switch um and we have our expansion Port
[5:12] so I’m really excited about this
[5:14] expansion Port I think we might have to
[5:15] do something quite interesting with this
[5:17] but uh that will be for a future video
[5:19] and we have the two connectors for the
[5:21] displays so I’ve got two displays I’m
[5:23] looking at one of them has 18 pins and
[5:26] the other one has I think that’s 10 pins
[5:29] and these are also rooted out to the um
[5:31] expansion Port so that’s going to be
[5:33] quite interesting um so yeah so need to
[5:37] get this sent off to PCB way now and uh
[5:40] hopefully I’ve not made any mistakes
[5:41] I’ve double checked everything I think
[5:43] it’s correct um everything looks right
[5:45] schematic match is all the DLCs are
[5:47] right so fingers crossed I’ve not messed
[5:49] it
[5:51] [Music]
[5:52] up so the uh new boards have arrived
[5:55] from PCB way and I have to say they look
[5:58] absolutely fantastic so here’s our new
[6:00] um ic’s that do all the attouch
[6:02] multiplexing they worked out so cheap
[6:04] it’s incredible I think I got these for
[6:06] 20 cents a piece um so that’s amazing
[6:09] doesn’t add much to the bomb at all now
[6:11] um it’s the PCB way 10th anniversary so
[6:14] if you want some pcbs you should go over
[6:16] and check them out they are really great
[6:18] I can recommend them I mean they’ve made
[6:19] this what more can you ask for so let’s
[6:21] test out the actual keyboard so let’s
[6:24] have a look go into basic and let’s try
[6:27] and WR something so let’s do the old
[6:29] hello world
[6:30] so now I should be able to use symbol
[6:31] shift and P to get quotes and that
[6:34] actually works and I can shift and zero
[6:37] for delete
[6:39] hello world uh symbol shift p and then
[6:44] symbol shift o for a um oh let’s put a
[6:47] space in space symbol shift B symbol
[6:50] shift o it’s working brilliantly um this
[6:52] is absolutely
[6:54] amazing there we go hello world oops
[6:57] hello world 10 looks like I can’t basic
[7:00] anymore print 10 so let’s see how do we
[7:02] do edit uh so that’s one
[7:07] no edit there we go cool it’s coming
[7:10] back to me so go to 10 enter run there
[7:15] we go hello world it works let’s try a
[7:18] quick
[7:19] game okay manic
[7:26] Miner so the keyboard’s really
[7:28] responsive as well even though we’re
[7:30] having to scan it it’s still amazingly
[7:32] good so this is brilliant I think we’re
[7:34] actually pretty close to a production
[7:36] version so I’m going to get on and uh
[7:38] finish this off and then try and get
[7:40] this on sale um I think um oops not very
[7:44] good at manic Miner anymore but uh yeah
[7:46] so I’m going to try and get this on sale
[7:48] as soon as possible I think we’re pretty
[7:49] good to go um the display all works and
[7:52] the display is pretty nice it’s quite
[7:53] big um and I’ve got a few ideas for this
[7:56] expansion Port but that will be in a
[7:58] future video so thanks for watching it
[8:01] works and it’s fantastic