[cctalk] Re: Pertec controller; was: anybody need 1/2" tape drives?
On Wed, Nov 30, 2022 at 08:10:27PM -0500, Paul Koning via cctalk wrote: [...] > 5V tolerant does not mean 5V compatible. I have right now some 5V devices > I want to control, and it's not exactly clear whether a 3.3V device will > drive outputs high enough to reliably make 5V devices see them as high. > Arduinos can be had in actual 5V models (5V power, standard 5V logic > levels in and out). Not the fast ARM ones but for many purposes good > enough. There's no single "standard 5V logic levels". The usual comparison is between TTL and CMOS of course, but there are also the subfamilies which are mostly compatible, right up until they aren't. Anyway, you can usually drive a TTL(-compatible) input from a 3.3V output because TTL treats anything above 2V as a logic 1. The "usually" caveat is because there are pathological devices out there, so check those datasheets to see if they're compatible. In particular, some microcontrollers can only source limited current and some rare old TTL devices are quite thirsty. (At least they won't get rarer if you try this, as you'll burn out the microcontroller first.)
[cctalk] Re: Pertec controller; was: anybody need 1/2" tape drives?
On 12/1/22 05:35, Peter Corlett via cctalk wrote> > Anyway, you can usually drive a TTL(-compatible) input from a 3.3V output > because TTL treats anything above 2V as a logic 1. The "usually" caveat is > because there are pathological devices out there, so check those datasheets > to see if they're compatible. In particular, some microcontrollers can only > source limited current and some rare old TTL devices are quite thirsty. (At > least they won't get rarer if you try this, as you'll burn out the > microcontroller first.) A more significant issue is the substitution of 74HC for 74HCT logic in applications driven by TTL in bus applications, where the loading can be significant. Vih min tends to be around 3 volts for HC devices. Bottom line is that you may be able to get away with using an HC instead of an HCT device as a TTL bus receiver, but don't count on it always working. --Chuck
[cctalk] Re: Pertec controller; was: anybody need 1/2" tape drives?
> On Dec 1, 2022, at 8:35 AM, Peter Corlett via cctalk > wrote: > > On Wed, Nov 30, 2022 at 08:10:27PM -0500, Paul Koning via cctalk wrote: > [...] >> 5V tolerant does not mean 5V compatible. I have right now some 5V devices >> I want to control, and it's not exactly clear whether a 3.3V device will >> drive outputs high enough to reliably make 5V devices see them as high. >> Arduinos can be had in actual 5V models (5V power, standard 5V logic >> levels in and out). Not the fast ARM ones but for many purposes good >> enough. > > There's no single "standard 5V logic levels". The usual comparison is > between TTL and CMOS of course, but there are also the subfamilies which are > mostly compatible, right up until they aren't. > > Anyway, you can usually drive a TTL(-compatible) input from a 3.3V output > because TTL treats anything above 2V as a logic 1. Good point. In the one application I did earlier where I chose the 5V Arduino is a PS2 keyboard to LK201 converter, where I'm dealing with keyboards whose internals are unknown and might not be particularly tolerant of oddball levels. The one I'm looking at now involves driving either HCT chips or digital radio ASICs (HSP 50214/50215). The latter clearly say 2V is high enough, and input currents are just a few microamps. The other difficulty is inputs, if the MCU isn't 5V tolerant. Raspberry Pico isn't, for example. For input-only, a resistor divider is a sufficient solution. For bidirectional wires it gets complicated, in that case I'd probably have to use an honest to goodness translator IC. It looks like I dont have that case at the moment, though. paul
[cctalk] Re: Pertec controller; was: anybody need 1/2" tape drives?
On Wed, Nov 30, 2022 at 04:43:08PM -0800, Chuck Guzis wrote: > On 11/30/22 14:45, Eric Moore via cctalk wrote: > > I have a kennedy 9100 with an unformatted pertec interface that I would > > love to use for imaging tapes from my AS/400 > > > > It seems like strapping a logic analyzer to the read connector, and an > > arduino on the command connector, may be fairly easily done? Has anyone > > done that? > > I have to confess that I've never understood the Arduino thing. It > seems to be limiting the functionality of an MCU in the name of convenience. > It also gives portability across manufactures for the simple stuff and a consistant though not the most feature full enviornment that is the same for each board. You can use the low level functions of the chips if you want but then it won't be portable. Also a good amount of how to do X with it online. I use it for that reason. Good for small projects. I've used manufacturer specific enviornments in the past but see no need to. Last project was some remote sensors using ESP32. $8 for the board. Arm processor.
[cctalk] Re: Pertec controller; was: anybody need 1/2" tape drives?
*ESP32 = Xtensa core https://dl.espressif.com/github_assets/espressif/xtensa-isa-doc/releases/download/latest/Xtensa.pdf On Thu, Dec 1, 2022, 2:59 PM David Gesswein via cctalk < cctalk@classiccmp.org> wrote: > On Wed, Nov 30, 2022 at 04:43:08PM -0800, Chuck Guzis wrote: > > On 11/30/22 14:45, Eric Moore via cctalk wrote: > > > I have a kennedy 9100 with an unformatted pertec interface that I would > > > love to use for imaging tapes from my AS/400 > > > > > > It seems like strapping a logic analyzer to the read connector, and an > > > arduino on the command connector, may be fairly easily done? Has anyone > > > done that? > > > > I have to confess that I've never understood the Arduino thing. It > > seems to be limiting the functionality of an MCU in the name of > convenience. > > > > It also gives portability across manufactures for the simple stuff and > a consistant though not the most feature full enviornment that is the same > for each board. You can use the low level functions of the chips if you > want > but then it won't be portable. Also a good amount of how to do X with it > online. > > I use it for that reason. Good for small projects. > I've used manufacturer specific enviornments in the past but see no need > to. > > Last project was some remote sensors using ESP32. $8 for the board. Arm > processor. >
[cctalk] Re: Pertec controller; was: anybody need 1/2" tape drives?
On 12/1/22 11:02, David Gesswein via cctalk wrote: > It also gives portability across manufactures for the simple stuff and > a consistant though not the most feature full enviornment that is the same > for each board. You can use the low level functions of the chips if you want > but then it won't be portable. Also a good amount of how to do X with it > online. Don't a few libraries do that without saddling you with a development environment? I use opencm3 for a lot of ARM-related simplish MCU things. There was a stm32duino group, but it seems to have gone moribund. It appeared to concentrate mostly on the "blue pill" platform as well as the older Maple mini boards (anyone need any of those?) I had a brief encounter with the PIC32 Arduino Uno from Digilent, but I wasn't taken by it. --Chuck
[cctalk] Re: Pertec controller; was: anybody need 1/2" tape drives?
On 12/1/2022 12:34 PM, Chuck Guzis via cctalk wrote: Don't a few libraries do that without saddling you with a development environment? I assume you mean the IDE? No reason to use that if you don't want to. On the rare occasions I do Arduino development (mostly on the excellent Teensy ARM boards) I use my preferred editor and a simple makefile. As I see it, the value of Arduino is in its ability to reach people who otherwise wouldn't be able to master embedded development, either because they lack sufficient training, or because they simply have better things to do with their time. I don't particularly need its simplicity, but I understand that others do. --Jay
