Hi Rich,
Yeah, I think it was even less than 2 years.? I believe I saw ads for IMSAI as early as Feb 1976 (13 months after ALTAIR's announcement Jan 1975).
On the topic of Octal vs HEX.? I might make some enemies here, but I believe HEX is better. The original owner of my Altair put (zippo) tape over every other 4 switches (HEX visual cues).
While the 8080 instruction set is geared towards Octal, I will dare to say it's easier to enter a program in HEX. Because in HEX, you only need to remember 2 characters.? I am guessing someone with a good memory (not me) could probably read and retain 8 bytes of data then enter them into the computer, while the same person might only be able to do 4 bytes of Octal. The only con about HEX are the letter codes... but with a little practice, those become 2nd nature.
Besides, I've never been a fan of 377 377, I mean, how can 377 377 be the same as 177777 ? I think most will agree HEX just fits in nicer.? Now if only we can change the alphabet..? 26 is such an odd number!
Here's a weird thought... what would computer programming look like if we still used Roman Numerals?
X? Print "Hello" XX Goto X
LoL
|
Re: Running and returning
Bob Kircher wrote in,
"If I were to write a program to run on the Z80MC in high memory (not?
under CPM) what is the preferred way to return to the monitor?? I had?
been using JP 0042H ( JP VMAIN_MENU ) but I recently discovered I can?
not change any registers after I get back to the monitor.? I can also?
return by jumping to location zero but I'd better be quick about hitting?
the M key else I accidentally boot CP/M."
Great question, worth posting to the forum.
I'm not 100% sure what I wrote and debugged but having a quick look at the source code it appears only execution to 0000 will save the registers.
As such, when executing the G command, the monitor places 0000 on stack as the return address.? So your code needs to only RET to get back to the monitor.
LD HL,0 ;10 Set Default return address as 0000 (Restart/Save Registers) PUSH HL ;11? ?& Put on stack
Now, it should know/resolve the restart type and not prompt you to press M for monitor... but I'm not sure if that works... certainly won't be the only bug in the system.? If you really want, you can fake the M key by entering it into the buffer yourself before returning to 0000.
Here's a snipit of the code that saves the bit banged character to the buffer.??
IRXD_SAVE LD? A,H ;4 ;Fetch received byte LD? HL,(RXBHEAD) ;16 ;Advance Head Ptr of RX Buffer, Head = Head + 1 INC L ;4 LD? (RXBHEAD),HL ;16 LD? (HL),A ;7 ;Save Received byte into RX Buffer
Actually, instead of faking the M key, you can set the SOFT_RST_FLAG value (I think the firmware might already be doing this.. but I cant' figure out where).
When the firmware boots up, it runs code to check this flag as follows. If you set this flag to 0xD1 (single step return), it should return to the monitor and automatically dump the registers.
;Determine why the CPU is executing A RESET. ;? -Power on (RAM signature will be wrong) ;? -F-0 Reset Switch (one of the switches will still be pressed) ;? -RST 0 (look for C7 at previous location given by stack) ;? -External /RESET OR User program branches to 0000 ; ;RC_TYPE ;0 COLD RESET (NO RAM SIGNATURE) ;1 F-E Soft Reset (SOFT_RST_FLAG = FE) ;2 Single Step (SOFT_RST_FLAG = D1) ;3 <Ctrl>-C (SOFT_RST_FLAG = CC) ;4 HALT (SOFT_RST_FLAG = 76) ;5 F-0 (F or 0 key on FP still down) ;6 RST0 ( M(PC-1) = C7) ;7 HARD RESET (Default if SOFT_RST_FLAG not set)
Hopefully the RET should work fine, but if not, it's definitely one of the things I will be addressing in the next version of firmware.
Regards, Josh
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Just compare the Altair to the IMSAI front panels. They are separated by 2-3 years and the grouping changed from an octal grouping to a hex grouping.
I’ve seen a few Altairs in which the user put colored toggle caps (remember those from Radio Shack?) on the switches to improve the toggling speed through visual cues. That’s why I think the IMSAI front panel is a stroke of genius
— the visual cues and grouping made toggling easier (IMHO).
Get
?
toggle quoted message
Show quoted text
I should note... the original idea of using colours for HEX / Octal wasn't mine, I got it from the IMSAI 8080, the switches could be re-arranged for HEX or Octal.? I'm not sure if that was an original idea in 1976 either, it really never ceases
to amaze me of how many ideas for modern computers came from the 50's and 60's.??
Paul,
I should have mentioned that the Altaid is capable of running CP/M.? It does not have the flexibility that is available with the Z80MC, but the firmware expects 512K of RAM.?
NO SD card, just a big RAM disk.? The first 64K of RAM is for system and the remaining 448K is used as a RAM Disk.? You may Xmodem load/save this RAM Disk
image.? It comes with 2 programs preloaded, PIP and XM (Xmodem to transfer individual files to/from the disk).
XM is a simplified small version of Martin Eberhard's XModem.?
Josh
On Wednesday, November 20, 2019, 2:44:18 p.m. CST, Paul Bigwood <paul@...> wrote:
Lee,
?
I was very interested in the G Barrow 8080 S100 board octal display and keypad. A Google search turned up the user manual with cct and rom code.
I first learnt octal coding when i worked at DEC as a field service engineer in the uk in the '80s, and had forgotten how opcodes could be decoded and encoded easier using octal compared to hex.?
Octal was very popular when the 8080 first came out.?
I wondered if it is possible to space the address bus and data bus LEDs in octal spacing rather than binary/hex making it easier to enter and read the LEDS in octal. e.g. Data LEDs and switches are spaced?
Like this? XX XXX XXX? rather than XXXXXXXX. Same applies for Address bus. Vis
Address bus XX XXX XXX XX XXX XXX rather than the XXXXXXXXXXXXXXXX.
Is it planned to add a SD card for cp/m??
Best regards
Paul G3WYW?
As i understand the existing code,? the bus input switches toggle the associated?
R
?
Sent from Samsung tablet.
|
I should note... the original idea of using colours for HEX / Octal wasn't mine, I got it from the IMSAI 8080, the switches could be re-arranged for HEX or Octal.? I'm not sure if that was an original idea in 1976 either, it really never ceases to amaze me of how many ideas for modern computers came from the 50's and 60's.??
Paul,
I should have mentioned that the Altaid is capable of running CP/M.? It does not have the flexibility that is available with the Z80MC, but the firmware expects 512K of RAM.? NO SD card, just a big RAM disk.? The first 64K of RAM is for system and the remaining 448K is used as a RAM Disk.? You may Xmodem load/save this RAM Disk image.? It comes with 2 programs preloaded, PIP and XM (Xmodem to transfer individual files to/from the disk). XM is a simplified small version of Martin Eberhard's XModem.?
Josh
On Wednesday, November 20, 2019, 2:44:18 p.m. CST, Paul Bigwood <paul@...> wrote:
Lee, ? I was very interested in the G Barrow 8080 S100 board octal display and keypad. A Google search turned up the user manual with cct and rom code.
I first learnt octal coding when i worked at DEC as a field service engineer in the uk in the '80s, and had forgotten how opcodes could be decoded and encoded easier using octal compared to hex.?
Octal was very popular when the 8080 first came out.?
I wondered if it is possible to space the address bus and data bus LEDs in octal spacing rather than binary/hex making it easier to enter and read the LEDS in octal. e.g. Data LEDs and switches are spaced? Like this? XX XXX XXX? rather than XXXXXXXX. Same applies for Address bus. Vis Address bus XX XXX XXX XX XXX XXX rather than the XXXXXXXXXXXXXXXX.
Is it planned to add a SD card for cp/m??
Best regards
Paul G3WYW?
As i understand the existing code,? the bus input switches toggle the associated?
R ?
Sent from Samsung tablet.
|
Paul Bigwood wrote: It would be good if the ROM monitor could .support both Hex and Octal,
but understand the issues. It's one of those "someday..." things. My Heathkit H8 and H89 computers both support both octal and hex displays. The H8 uses two different ROMs (2K each). The H89 has a bigger ROM (4K) that has a "radix" command to select octal or hex. I was thinking of a SD card for program storage under cp/m, but now
realise your design objective for this computer to be truly retro, so
'cassette' storage is required. It's not required, but it's there for that "vintage feel". However, the Altaid's RAM has battery back-up. You initially load it via the serial port (from a PC etc.) Once it's loaded, the battery maintains data even with the power off. Looking forward to the kit being available soon. So are we! :-) Lee -- ICEs have the same problem as lightbulbs. Why innovate and make better ones when the current ones burn out often enough to keep you in business? -- Hunter Cressall -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Hi Lee and Josh,
Different colored LEDS would do the same. Grest idea.
It would be good if the ROM monitor could .support both Hex and Octal, but understand the issues.
Yes, that was the site for George Morrows 8080 S100 board with display and keypad.
I was thinking of a SD card for program storage under cp/m, but now realise your design objective for this computer to be truly retro, so 'cassette' storage is required.?
Looking forward to the kit being available soon.
Best Regards
Paul.
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Paul Bigwood wrote: Lee,
I was very interested in the G Barrow 8080 S100 board octal display
and keypad. A Google search turned up the user manual with cct and
rom code. Do you mean George Morrow's "Keyed-Up" combination front panel and 8080 CPU board? This one? <> joshbensadon via Groups.Io wrote: There is barely enough space for the LED's they're packed in there like
commuters on the 5 O'clock train!
But, you can very easily alternate colours of LED's. I'm using Red and
Yellow, in sets of 4 for HEX.
Nothing stopping you from doing sets of 2,3,3. Might need to count out
the right number of LED's for both layouts. That's a good idea. :-) The LEDs are evenly spaced, so color could be used to separate them into hex or octal formats. It should be easy to supply enough LEDs so the builder can choose which he wants. The serial monitor is a little harder. Right now, it's written for hex. But the source is available, so you could change it for octal. Is it planned to add a SD card for cp/m? The Z80MC already has it. If you mean the 8080 "Altaid 8800", it doesn't have an SD-card... or for that matter, *any* modern parts. I was aiming for a pure retro-design. It does have jumper options for bigger modern "bytewide" RAMs and ROMs. In 1976 (the ficticious introduction date), the only options would have been a 2716 2K EPROM and 2K RAM (and they were both very new and expensive). But as Intel's Gordon Noyce observed, memory chip size doubled every 2 years! -- ICEs have the same problem as lightbulbs. Why innovate and make better ones when the current ones burn out often enough to keep you in business? -- Hunter Cressall -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Hi Paul, There is barely enough space for the LED's they're packed in there like commuters on the 5 O'clock train! But, you can very easily alternate colours of LED's.? I'm using Red and Yellow, in sets of 4 for HEX. Nothing stopping you from doing sets of 2,3,3.? Might need to count out the right number of LED's for both layouts.
On Wednesday, November 20, 2019, 3:44:18 PM EST, Paul Bigwood <paul@...> wrote:
Lee, ? I was very interested in the G Barrow 8080 S100 board octal display and keypad. A Google search turned up the user manual with cct and rom code.
I first learnt octal coding when i worked at DEC as a field service engineer in the uk in the '80s, and had forgotten how opcodes could be decoded and encoded easier using octal compared to hex.?
Octal was very popular when the 8080 first came out.?
I wondered if it is possible to space the address bus and data bus LEDs in octal spacing rather than binary/hex making it easier to enter and read the LEDS in octal. e.g. Data LEDs and switches are spaced? Like this? XX XXX XXX? rather than XXXXXXXX. Same applies for Address bus. Vis Address bus XX XXX XXX XX XXX XXX rather than the XXXXXXXXXXXXXXXX.
Is it planned to add a SD card for cp/m??
Best regards
Paul G3WYW?
As i understand the existing code,? the bus input switches toggle the associated?
R ?
Sent from Samsung tablet.
|
Lee, ? I was very interested in the G Barrow 8080 S100 board octal display and keypad. A Google search turned up the user manual with cct and rom code.
I first learnt octal coding when i worked at DEC as a field service engineer in the uk in the '80s, and had forgotten how opcodes could be decoded and encoded easier using octal compared to hex.?
Octal was very popular when the 8080 first came out.?
I wondered if it is possible to space the address bus and data bus LEDs in octal spacing rather than binary/hex making it easier to enter and read the LEDS in octal. e.g. Data LEDs and switches are spaced? Like this? XX XXX XXX? rather than XXXXXXXX. Same applies for Address bus. Vis Address bus XX XXX XXX XX XXX XXX rather than the XXXXXXXXXXXXXXXX.
Is it planned to add a SD card for cp/m??
Best regards
Paul G3WYW?
As i understand the existing code,? the bus input switches toggle the associated?
R ?
Sent from Samsung tablet.
|
ajparent1/kb1gmx wrote: With 8080 RST7 is free (bus to 1s using pullups) Yep! That's how I did it on the Altaid 8800 (an 8080 version of Membership Card) <>. But that has to change to make stock versions of DDT (or SID or ZSID) work. For the Z80MC, DRI application note #07 is the patch to change DDT to use RST6 instead of RST7. We made the patch, and put a copy of DDT with it (named DDT-V6.COM) on the DISK-1 image for the SD-CARD. Josh has also updated his Windows CP/M Explorer program to version 1.3. Both have been uploaded to the website <> DDT is a very compact program as well. It certain is! There are some very clever tricks to keep it small. Whoever the programmer was (Gary Kildall himself?), he certainly knew how to code for limited resources. heath H8 the front panel was a source of issue for later software. It
was its weakness in the works of Altair and IMSAI. It depends on what you want. Front panels are expensive and hard to use; after the initial novelty wears off, they don't get used much. The Heath H8 keypad and 7-seg LED monitor was a lot easier to use; and cheaper, too. It remained useful on a regular basis. For one thing, it would continuously display the last register, memory address, or I/O port even while your main program ran. But as you say, it depended on an interrupt, and for the CPU to be running the monitor program. It took away a little execution time (but you could turn it off to make your programs run a little faster). One of the cleverest early Front Panels was George Morrow's "Keyed-Up". It was an 8080 CPU board for the S-100 bus that included a keypad and 7-seg display. It ran software to work; but that software was a tiny 32-byte PROM. Instead of depending on an interrupt, it opened the 8080 data bus, and inserted its PROM. The card had a separate program counter for the PROM; it didn't depend on the CPU's PC. So his little program ran no matter where the CPU was, to let you examine and change memory, etc. Lee -- There is a computer disease that anybody who works with computers knows about. It's very serious, and interferes completely with your work. The trouble with computers is that you 'play' with them! (Richard Feynman) -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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With 8080 RST7 is free (bus to 1s using pullups) if you want any other you need to assert that on the bus
an octal bus driver with the inputs set to RST3 or 4 is suggested.? RST6 is also in a sorta sometimes
used space as well.?
DDT is a very compact program as well.
heath H8 the front panel was a source of issue for later software.? It was its weakness in the works
of Altair and IMSAI .? Both of them the lights for address were just buffers address the Data leds?
were also same and the processor wait stated between operations.
Most of the "smart" front panels the address leds were again off the address bus
but the data was a latched port? both input and output and the very small usually 256 bytes?
program interrogated switches or loaded the latch. Most all avoided interrupts as they were
difficult (who knows what CPU) and often got in the way.? When running the leds show data
and address off the bus and the FP know if it was running or suspended.
the 8080 FPs often used tricks like 1802 DMA load mode save for it was done via wait and?
jamming nop or jumps for a single cycle.
Allison
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ajparent1/kb1gmx wrote: Having a [Front Panel] should be seamless, least it was on my old
Altair when it behaved. There is no reason why CP/M should not run
with a FP. Also the blinkin lights thing. Yes; the blinkin-lights are an important feature of a FP. "What are all those blinking lights doing, son?" "Impressing you, dad!" A hardware front panel shouldn't have any effect on the computer. But a software-driven front panel (like the Z80MC or a Heath H8) has to interact. It needs a program in memory to run it, and an interrupt to periodically update the blinkin-lights. The interrupt routine requires time, and that there be a working stack, among other things. The Z80MC uses RST7 for its timer/serial/front panel interrupt. We just discovered that CP/M's DDT also uses RST7 for breakpoints. Thus they conflict; so DDT will crash the system! There are a couple ways to fix this: 1. Software: I've been looking at the DDT source, and there is an option to use RST6 instead of RST7. DRI apnote #7 (attached) describes the procedure for patching DDT to use RST6. It says to change address 01EB from FF to F7. But, Bob Kircher reports that his copy of DDT had the FF at 01EC (not 01EB). So he patched to 01EC from FF to F7; and it worked. :-) 2. Hardware: It is also possible to move the hardware interrupt from RST7 to some other interrupt. But this requires some cuts-n-patches, plus some software changes to the ROM and BIOS to account for it. So I think we'll save that for a future revision. DDT loads to 100H then senses the base of BDOS and relocated
to under that so the space from 100h to below DDT is available for
user programs that would nominally be at loaded at 100H when
finished or debugged. Yes; DDT is a *very* clever program! The source has been published ro all to see. Besides relocating itself, it can also allow the program it is debugging to overlay parts of it, and still keep the remaining parts working. Lee -- There is a computer disease that anybody who works with computers knows about. It's very serious, and interferes completely with your work. The trouble with computers is that you 'play' with them! (Richard Feynman) -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Yes, having A FP should be seamless, least it was on my old Altair
when it behaved.? There is no reason why CP/M should not run
with a FP.? Also the blinkin lights thing.
The Xmodem bug,? That may be a feature. ;)? Modem program in
the CP/M space were always troublesome as some wanted a well
configured IO byte, others did direct IO and had to be tweaked for
the IO device in use (SIO-A or B, 8251, 6850, 2651, 16450,
SIO/(drt or SIO2)? and many others often different enough.
DDT the likely clash is RST7 (address 38) as DDT uses that as a
debug return point.? ?Usually front panels had port FFh as an input
from the FP switches (sense, often used by non cpm for setting up
what IO exists).? Also FFH is the opcode for RST7 so missing memory
(altar/imsai) has pull-ups so by default no ram, is a RST7.
FYI the most nasty bug on the Altair was noise on all the front panel
wires to the bus causing the appearance of "flying bits" and crashes.?
DDT loads to 100H then senses the base of BDOS and relocated
to under that so the space from 100h to below DDT is available for?
user programs that would nominally be at loaded at 100H when
finished or debugged.
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Hi, I've been going over some bugs that Bob Kircher has been encountering. There are 4 bugs identified 1. Some sort of Buffer problem (I need to dig into much earlier emails to recall this problem)? No action has been taken. 2. CP/M XModem not working.? This is the XModem that is on the DISK-A image.? It's Martin Eberhard's XModem, very nicely written and configurable.? It will need the correct XModem.cfg file with the following
/X2?? ?;use custom port defined here
/Z2?? ?;2 MHz CPU /E?? ?;RDR port returns with Z set when no chr waiting /MDirect I/O is configured for Z80MC ACE Port /P CD C8 01 01 20?? ?;Port A /Q 3. CP/M Programs that use the alternate register set will not work.? This is because the ISR that runs for the bit banged serial and the Front Panel Timer / LED driver is using the alternate register set.? This was done to improve response time to the point where serial data can be reliably received.? While the ISR mainly (solely) uses the A and HL registers, there are other things that make it complicated, namely the bank switching as you never know if the CPU is running from ROM or RAM at the time of an ISR.? A possible fix for #3 is to turn off the interrupts.? This of course can be done by simply running the SIO and CPU cards without the FP board (the firmware will never receive an interrupt).? Another (less attractive) fix is to re-code the program to not use alternate registers (but this is more complex, needs source code and hopefully it isn't constrained by the quick timing possible when using alternate registers).
4. DDT debugger is not working.? This is a bug related to #3, because if you run CP/M without the FP board, this program also works. Some how related, this is also a bug on the new ALTAID 8800, and it's also resolved by turning off Timer Interrupts.
But not a bug on the JAIR system (which doesn't use any interrupts).
This will be a more tricky bug to solve.? The ALTAID runs on an 8080, so it does not have any Alternate Register set, but some how the changing RAM (scan lines) is affecting DDT.? Perhaps DDT is using High RAM for scratch? Comments / questions by Bob:
a. So running CP/M without the front panel is certainly an option.?
b. I'm sure Lee's not thrilled about it though; that front panel is a
nifty piece of work.?
c. Admittedly though it's far more useful
running programs with the monitor and only limited usefulness with
CP/M.
d. Would increasing the interval between timer interrupts help??
Would it even be practical?
e. Ideally we should be able to run anything under CP/M with the
front panel attached.
I agree, getting the FP running seamlessly with CP/M is a worthy goal. Timer interrupt interval is fixed by hardware and corresponds with the LED display scanning.
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Easier would be the smaller T-11 as its a more conventional 40pin.
Allison
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Paul Bigwood wrote: Hi Lee, Love it [Altaid 8800]. Do you have prices and availability of a kit yet? TBD (To Be Detirmined). But hopefully by the end of the year. :-) Price will be similar to my other little computers (1802 and Z80). Lee80 Hart -- There is a computer disease that anybody who works with computers knows about. It's very serious, and interferes completely with your work. The trouble with computers is that you 'play' with them! (Richard Feynman) -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Hi Lee,
Love it.
Do you have prices and availability of a kit yet?
Best Regards
Paul?
Sent from Samsung tablet.
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All good updates! Thanks Lee!
Get
?
toggle quoted message
Show quoted text
I recently updated the Z80 Membership Card CPU card to rev.B, and the
Front Panel card to rev.D. No big changes; but here are the improvements:
CPU rev.B
The 5v regulator U8 has been flipped upside down, so its metal tab faces
up (away from the board) instead of down (against the board). This
improves its ability to dissipate heat if you're running with an
unregulated 6-9vdc supply.
I added a 6-pin power/serial connector P4. Its pinouts are the same as
P4 on on the Front Panel, so a Sparkfun 5v USB-serial cable #9718 plugs
right in. This connector is located in the same place as U8; so install
one or the other (not both). If you are getting 5v power from the
USB-serial cable, then you don't need the U8 regulator.
P3 was added to jumper the serial input to the Z80 /INT input. This
connection was made on the Front Panel; but with the P3 jumper, you can
use the CPU board all by itself (no front panel). Use a serial terminal
to talk to the monitor or run BASIC or other programs.
Options were added to jumper bus P2 pin 28 to HALT or /BUSAK, and bus P2
pin 29 to /NMI or BUSRQ. This provides access to these pins if needed
for your own accessory cards.
Front Panel rev.D
I replaced the hard-to-find LED-photoresistor coupler with a standard
LED-phototransistor coupler. This required a new pulllup resistor, R2D.
The optocouplers I bought seem to have a little too much gain. Some
users have found that they can still hear the piezo when it should be
off. My hearing isn't good enought to tell! If you hear it, try a lower
value pullup for R2D, or replace the optocoupler with a lower-gain part.
Forward into the past,
Lee Hart
--
There is a computer disease that anybody who works with computers knows
about. It's very serious, and interferes completely with your work. The
trouble with computers is that you 'play' with them! (Richard Feynman)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
|
I recently updated the Z80 Membership Card CPU card to rev.B, and the Front Panel card to rev.D. No big changes; but here are the improvements:
CPU rev.B
The 5v regulator U8 has been flipped upside down, so its metal tab faces up (away from the board) instead of down (against the board). This improves its ability to dissipate heat if you're running with an unregulated 6-9vdc supply.
I added a 6-pin power/serial connector P4. Its pinouts are the same as P4 on on the Front Panel, so a Sparkfun 5v USB-serial cable #9718 plugs right in. This connector is located in the same place as U8; so install one or the other (not both). If you are getting 5v power from the USB-serial cable, then you don't need the U8 regulator.
P3 was added to jumper the serial input to the Z80 /INT input. This connection was made on the Front Panel; but with the P3 jumper, you can use the CPU board all by itself (no front panel). Use a serial terminal to talk to the monitor or run BASIC or other programs.
Options were added to jumper bus P2 pin 28 to HALT or /BUSAK, and bus P2 pin 29 to /NMI or BUSRQ. This provides access to these pins if needed for your own accessory cards.
Front Panel rev.D
I replaced the hard-to-find LED-photoresistor coupler with a standard LED-phototransistor coupler. This required a new pulllup resistor, R2D.
The optocouplers I bought seem to have a little too much gain. Some users have found that they can still hear the piezo when it should be off. My hearing isn't good enought to tell! If you hear it, try a lower value pullup for R2D, or replace the optocoupler with a lower-gain part.
Forward into the past,
Lee Hart
--
There is a computer disease that anybody who works with computers knows
about. It's very serious, and interferes completely with your work. The
trouble with computers is that you 'play' with them! (Richard Feynman)
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
|
timgreenowb via Groups.Io wrote: Just joking. I forgot to put a smiley ? on my post. It's the chip
from a DEC PDP-11 and obviously wouldn't fit in a tin. Well, there are PDP-8 and PDP-11 clone kits (google PiDP-8 or PiDP-11). They use a Raspberry Pi as their "brain", which would fit in an Altoids tin. Almost *everything* has been put in an Altoid tin. I had a mad idea to put one of those tiny 12vdc-to-120vac inverters that plug into an auto accessory (cigarette lighter) socket in an Altoids tin, along with 12v worth of rechargeable batteries and a small PV panel. When the sun shines on it, you have a "nuclear power plant" in an Altoids tin. :-) Lee Hart -- There is a computer disease that anybody who works with computers knows about. It's very serious, and interferes completely with your work. The trouble with computers is that you 'play' with them! (Richard Feynman) -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Lee Hart
Paul Bigwood