I look at this schematic of the HP48SX:
https://www.hpcalc.org/details/3543
It shows that the screendriver-circuit are two SED1181 serial connectet.
I think that is unusual because the datasheet of the SED1181 claims that
it build together with an SED1191 for a matrix-lcd.
I wonder if it is possible to grab the two data-bit in a microcontroller
and translate it for an oled for a much better readable display.
Did knows the code that generate the LCD-Signal to the output bits?
I still like my old HP48, but the low contrast of the early graphic-lcd,
are very poor by todays standard.
Of course it is now only an idea. :-)
Olaf
Hi Olaf, I Think your idea is definitely possible. Since the data sheet of
SED1181 is obtainable, we may just use one STM32, or any other kind of
micro-controller, to build an converter.
I just got a set of HP48 with keyboard problem, I may attempt to dissemble
it and go forward to build a converter. It sounds a fun little project to
do.
Jerry Xu <jerryxu@sdf.org> wrote:
>Hi Olaf, I Think your idea is definitely possible. Since the data sheet of
I know that it is possible because I connected my Logicanalyzer to the datastream. :-D
>SED1181 is obtainable, we may just use one STM32, or any other kind of
>micro-controller, to build an converter.
It is not so easy. The HP sends 2x67bits. ARGH! That is a little
bit unusual for traditional SPI Hardware in any controller.
Perhaps with RP2040 or an CPLD/FPGA. But in this case we have
to think a little bit about power consumption. .-)
>I just got a set of HP48 with keyboard problem, I may attempt to dissemble
>it and go forward to build a converter. It sounds a fun little project to
>do.
Strange, I have many HP48 because I bought them wenn they are cheap,
but I have never seen a keyboard problem. Only the HP49 ist famous for
it and I have a 49 with broken Keyboard.
I don't know if you are aware but HP produced an overhead projector
You could try using this to prototype your OLED display adaptor and then
modify it to get signals direct from the 48 once it is working?
5 VCO
6 XSCL
7 LP
8 LD0
9 LD1
10 GND
I started on an Arduino project to read the signals and then
(eventually) Bluetooth the display to a PC, got so far and then got
distracted by other projects!
I started on an Arduino project to read the signals and then
(eventually) Bluetooth the display to a PC, got so far and then got
distracted by other projects!
Bruce Horrocks <07.013@scorecrow.com> wrote:
>I started on an Arduino project to read the signals and then
>(eventually) Bluetooth the display to a PC, got so far and then got
>distracted by other projects!
I did some more investigation in the lcd data format but something strange happens in our old calculator. :)
The picture shows the dataline to the SED1181: (one row of 64)
http://www.criseis.ruhr.de/bilder/Datenpaket01.jpg
The schematic (https://www.hpcalc.org/details/3543) show that
there are two cascaded SED1181. That is understandable.
But one SED1181 has only 2x32Bit register, so two of them provide
2x2x32bit = 128bit for one row. This is to less, because the HP48
has 131pixel in one row.
But as you can see in my picture the Yorke put out 67x2=134pixel in one row. I am now very astonished where the calculator stores the extra pixel!
So I am now thinking if it is possile HP used a special SED1181 with
a bigger register.
Oh..and the datasheet for the SED1181 show an SED1191 for selecting the 64 rows.
This circuit did not exist in the HP48. But there are many unused
pin in the schematic, so I guess the Yorke did drive it directly,
but I did not checked it now.
Olaf
p.s: My measurement is taken on my special HP48SX with doubled clock.
So it is faster compared to an unmodified 48SX. .-)
p.s2: It is a shame that the spi-decoder in the RTB2004 can only decode
32bit and not 64 or 67, sigh.
p.s3: And why 131? That is a number that should not exist in the brain
of a hardware or software developer. :)
On 03/12/2022 19:37, olaf wrote:
p.s3: And why 131? That is a number that should not exist in the brain
of a hardware or software developer. :)
That bit is easy: the last character on the line doesn't need a blank
pixel column to separate it from the next character because there is no
next character.
Jerry Xu <jerryxu@sdf.org> wrote:
Hi Olaf, I Think your idea is definitely possible. Since the data
sheet of
I know that it is possible because I connected my Logicanalyzer to the datastream. :-D
SED1181 is obtainable, we may just use one STM32, or any other kind of
micro-controller, to build an converter.
It is not so easy. The HP sends 2x67bits. ARGH! That is a little bit
unusual for traditional SPI Hardware in any controller.
Perhaps with RP2040 or an CPLD/FPGA. But in this case we have to think a little bit about power consumption. .-)
I just got a set of HP48 with keyboard problem, I may attempt to
dissemble it and go forward to build a converter. It sounds a fun
little project to do.
Strange, I have many HP48 because I bought them wenn they are cheap, but
I have never seen a keyboard problem. Only the HP49 ist famous for it
and I have a 49 with broken Keyboard.
BTW: Ich bought my first HP48SX in 1990 for 700DM, in the first year I
pour out a cup of tea (with sugar) on it. I had to open it without
youtube video (looks strange since this opening), I dryed it, but never
opend the keyboard themself. It is still working! The first years the
keys felt a little bit rough because of the sugar, but the sugar is
pressed to dust and it feels like new in the last 20years. So I think
the keyboard is bulletproof.
Olaf
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