I think you would be much better off pulling power from the bar code port. I've successfully run a WiFi 232 off that port with a simple cable. Sure, it's not as pretty with another cable to connect, but it's still highly portable.
Or just run it off an AA battery and a boost regulator. Mark Blair is working on a device he calls the MicroTPDD that will do just that. I've seen early posts of the pcb layout on Twitter. On Thu, Aug 23, 2018, 8:02 PM Ken Pettit <[email protected]> wrote: > The series resistors in the Model T series portables are too large to > sipheon off anything but low micro amps. > > Ken > > On 8/23/18 4:37 PM, Brian White wrote: > > I'm playing with Teensy 3.5 and 3.6 myself right now. They have sd slot > built in and, and of course serial minus the max232, and seemingly gobs > more cpu and ram than needed for this task, considering what a real tpdd > itself has to do almost the same job. And unlike Tinyduino, the io pins are > all accessible directly, no extra breakout board shield needed to hook up > the max232-alike. And the "SdFat" add-on library now has native support for > the teensy 3.5/3.6 special sd reader. > > It seems like these controllers should not have any problem supporting > full normal fat32 filesystem and serial and tpdd server, but for lower-spec > controllers, it might be an interesting option to just forgo any filesystem > or even partition tables and just treat the sd card as raw space the same > way the tpdd itself does, like M1SE & M3SE do on Model I/III. It's a lot > less convenient for interoperability with other OS's, but it's still > interesting and potentially useful compared to an actual tpdd, without > requiring a full pc just to run a normal tpdd server. > > Another > challenge is power. Teensy 3.5/3.6 definitely draw way too much power to > scavenge from the serial port. But maybe > not... > Maybe > it's possible to have a tiny lipo that charges at > 5 or > 10ma while the M100 is turned on and the tpdduino is connected > but idle? > > Teensy 3.6 draws 80ma, plus the sdcard itself draws more but only very > briefly while operating, and a tiny drone lipo is 150mah, so it could run > the teensy for almost 2 hours of continuous use without even getting any > power from the M100. That already probably tranlates into days or weeks of > normal use between recharges, where the tpdd is really only active for 1 > second and then idle for 1800 seconds. So even without parasitic trickle > charging, just having a tiny built-in lipo and a microusb port to charge up > would already be good enough, but with that kind of extreme duty cycle > ratio like 1:1800, charging at even 5 or 10 ma in between transfers is > probably enough to keep the lipo charged all the time forever, other than > going dead on the shelf while turned all the way off for 6 months. > > I know modern max232 alternatives can power themselves entirely from the > serial port, have their own charge pumps & caps built-in, and power > themselves off when there is no serial activity, so the 3.3v or ttl to > rs232 would seem to be no problem, in terms of parts or power. > > > On Tue, Aug 21, 2018 at 5:49 PM Brian White <[email protected]> wrote: > >> This looks great! >> >> On Mon, Aug 20, 2018 at 4:31 PM c646581 <[email protected]> wrote: >> >>> I have a project that uses an Arduino Mega to emulate a TPDD. >>> >>> https://github.com/TangentDelta/SD2TPDD >>> >>> I have plans to eventually sell easy-to-use shields that provide the >>> RS232 level shifting and SD card interface. >>> >>> On Mon, Aug 20, 2018, 16:02 Brian White <[email protected]> wrote: >>> >>>> A tpdd emulated in low level basic hardware in line with the tpdd >>>> itself really appeals to me. >>>> >>>> I would love to try to make it work on a tinyduino, or maybe a gotek. >>>> Tinyduino may not seem "basic" being so small and modern, but it's a >>>> microcontroller not a PC. It doesn't run linux and systemd and bash and >>>> getty and python and a tcp stack and ssl and X and gnome etc etc etc. >>>> >>>> The fact that an entire pc fits in a tiny space and uses no power and >>>> costs $5 today thanks to the plain advancement over the passage of time, is >>>> sort of beside the point. Sure it's practical, but it's not *elegant*, in >>>> some intangible abstract mental way. >>>> >>>> You could run dlplus or laddie from an init script on an Omega2 and >>>> stuff the entire thing inside of a db25 connector shell, and probably even >>>> scavenge enough power right from the usb port with charge pumps, and the >>>> entire thing would be small and cheap and relatively easy to do, since it's >>>> just sticking a few existing things together like legos. Outwardly this >>>> makes all the sense in the world. But it's just such a brute-force kind of >>>> solution. I'd rather spend all kinds of time and effort to do the same >>>> thing with a controller in place of the computer. >>>> >>>> Though, you can sure get a lot more functionality out of a computer, >>>> like that virtual modem in mcomm. And the computer is infinitely more >>>> end-user hackable. It would be neat to play with hacking together some sort >>>> of front-end dispatcher script, kind of like inetd for serial or I guess >>>> that would just be an amped-up getty, maybe even with an interactive menu >>>> that you can access via TELCOM, and the front end runs a tpdd server or a >>>> dos injector or ssh client or lynx or virtual modem or something else and >>>> hooks it to the tty. It could stay in the loop monitoring the tty for >>>> special escape commands to break out into a command mode just like modems, >>>> telnet, ssh, cu etc all do, so you could always switch between functions >>>> from the M100 even after starting one. >>>> >>>> gahh ideas are sure easy to throw around :) >>>> >>>> >> >> -- >> bkw >> > > > -- > bkw > > >
