Yes it is nothing else. It is not the latest version that Dr_A has produced, this was a MK2 (probably) and I think he has got up to MK5++ by now. It allows for the whole 512KB of ram to be accessed via its driver. The "Baby" double sided version I did only allows for 64KB of ram to had, but it was for Z80 anyway. It emulates at about 2MHz Z80 eqivalent.
Heater, Clusso, Dr_A and Pullmore were the movers of this, and other memory arangements, over the last couple of years. I chose the DracBlade variaty because it all runs on one Prop . This has now got to the stage of quite a few old clasics being emulated.
I am quite excited to come back from holidays and work to the layout of the board. I wonder if I can manage to find room for the VGA connector, the PS2 connector, the SD card socket, the memory, the latches and the 138 decoder. Fortunately, the Prop, the RS232, the power supply and the EEPROM are already on the first board.
Yes that is the schematic link. @Toby, it is up to version 8 now. But the additions are minor - added a few more latch chips for general purpose I/O. Put in a socket for a mouse plug so you can choose mouse, or sound, or second serial port on those 2 pins. Added some pins for a radio link to other boards. And added some more D9 RS232 sockets so you can use the board as a RS232 router (something I'll probably need soon). (I haven't had that board made yet. I'm busy at the moment coding MPM into a text version of Windows).
I love watching a board being built this old-school way. The professional boards are fine, but they are very expensive if you only make a few, and it takes 10 days to get a board back. Single sided homebrew is something anyone can make themselves.
It is great watching Jean-Marie build this using tools we all have in the shed.
Is it possible to make the board bigger so everything fits? Or are you going to build this on lots of smaller boards and join them together?
I start out thinking of modular boards, but the inter connects are such a pain. So I end up with three modular boards that happen to have not been sawn off yet.
I did find that the new high speed SD software didn't lik the added capacitance of a 40 way IDE connector, and that was only 50mm long. random single wires would be slightly better.
Is it possible to make the board bigger so everything fits? Or are you going to build this on lots of smaller boards and join them together?
My first board is half the size of an euro board (thus 10 x 8 cm). I could use the full size (thus 10 x 16 cm ==> about 4 x 6.3 inches) if necessary. The most important thing is to put on one board the elements which have to stay always together. For example, the keyboard, the screen and the SD card can be thought to be always necessary.
I don't know if it would be more suitable to add the 512 K memory and the latches to the same board as the screen, keyboard, etc...or to put them on a separate board. Of course, it makes a difference. If everything is on the same board, there is no more free pin. So it becomes for example a problem to communicate with another controller. Indeed, not all utilizations need a large memory. I would like to have your opinion.
I did find that the new high speed SD software didn't lik the added capacitance of a 40 way IDE connector, and that was only 50mm long
I hope this will not be the case with the soft of the Dracblade Otherwise I would have to redraw another board with the SD card on the same board as the Propeller.
That is an interesting comment from Toby about the extra capacitance and SD cards.
I can add my experience to that - I had one board design where there was more than 3cm between the propeller chip and the VGA socket, and the screen had a lot more noise on it. So my designs now start by making the propeller chip as close to the VGA socket as possible (ie just enough room for the resistors). I also move the resistors a little until the autorouter comes up with a solution that does not route the vga signals via long routes.
I am not sure about the ram chip. The greatest distance for a high speed wire (ie P0-P7) on my board is about 10cm.
I am using a standard eurocard for my boards. I do not have a strong view about one big board versus two smaller boards one above the other. There are advantages for both.
Re If everything is on the same board, there is no more free pin. So it becomes for example a problem to communicate with another controller.
There are two ways to communicate. One is to use the serial ports and this is what I am doing for radio links. 9600 baud is fast enough for me!
The second is to add extra chips. See the attached pdf. This is a design I have not built yet, but it adds 8 TTL outputs and 8 TTL inputs. See IC16 and IC5. You could then use those chips to build a high speed parallel interface - possibly up to megabytes per second.
I might just mention on that pdf the transistor at the top left corner that is part of the download circuit. The 'standard' circuit uses a 547, but this circuit uses a 557 and there is a pull up resistor rather than a pull down resistor. (any small signal transistor will do). This circuit is pullmoll's clever design and came about due to some timing problems with the BST program. The technical problem is whether the propeller resets on the positive edge or the negative edge. Rather than asking the author to tweak the timing of BST (which I think caused other problems), this circuit solves the problem for no extra cost.
There are lots of things on that schematic you might not need, and you can't use all of the features at the same time. It brings out the propeller data lines to a header. Analog I/O to another header. 2 more serial ports (I am going to use the board to build a serial router, which is something clever the propeller can do with existing software and doesn't need external ram). The mouse is added, but you have to choose between mouse and second serial port. Also leds for P0-P7 - for a simple 'blinkenlights' propeller demo.
The problem I had with the SD and the IDE40 was that I had allowed for the 40way to take P0-P23 upto the top "memery experiments" board, the SD card was on a small daughter board on the lower level but also used P20-P23.
With the older, and slower, SD software all seemed ok, but when some wizard came along, and made it so much faster, this setup started to show signs of distress in that most of the time it wouldn't boot up the DracBlade system. Strangely if the Prop was cold (freezer spray) then it would work, otherwise it would not. Cutting the traces on the bottom board, to P20-P23 allowed proper operation at all times. The other wiring to the memory always worked ok.
Either it was the extra capacitance of the traces and IDE40 Wire(50mm)_Plug/Socket assembly or it might have been the unterminated stub that that wiring had formed. If it was purely the capacitance then carefully parting the individual 40 wires from each other would cut down the capacitance a bit (and make it a bit more flexible).
I must also add that I managed to get a DracBlade running on my "Lunchbox", photos were put onto the DracBlade thread. This was effectively a DemoBoard(ish) PCB wired to a breadboard by long trailing wires, and then with lots and lots of long jumper wires. NB this was with the older SD driver. If the cct could survive that sort of abuse then hopefully there should be no problems.
I had one board design where there was more than 3cm between the propeller chip and the VGA socket, and the screen had a lot more noise on it. So my designs now start by making the propeller chip as close to the VGA socket as possible
It'll not be possible to have less than 3 cm as I already have 2.7 cm on the first board between the pins of the Propeller and the ide connector. I must add to that a minimum of 1.3 cm flat ribbon and at least 2 cm for another ide connector and the resistors to the VGA socket. This makes a total of 6 cm.
Perhaps I should think over another layout for the base module, drawing my inspiration from your V5 or V8 schematic : I could keep together on the same PCB the Propeller, the EEPROM, the voltage regulators, the RS232, the VGA, the keyboard, the mouse/second serial port and the SD card and assemble on another board everything needed for the memory extension.
If Toby managed to build a Dracblade on a breadboard, I should manage to build one on 2 single side PCB.:rolleyes:
I must add that it was just a minimal approach. It only had two 8 bit latches, for 64KB memory. None of the LCD etc, etc, was put on. It did fire up CP/M though.
I was gob smacked, or whatever the equivilent in Belgium might be.
Sort of. "Gob" is English slang for mouth, so it's like being smacked in the mouth - something that is very surprising. Flabbergasted means the same sort of thing.
Toby, you young whipper snapper, there is nothing ancient about "flabbergasted".
From the Oxford English Dictionary:
First mentioned in 1772 as a new piece of fashionable slang; possibly of dialectal origin; Moor 1823 records it as a Suffolk word, and Jamieson, Suppl. 1825, has flabrigast to gasconade, flabrigastit worn out with exertion, as used in Perthshire. The formation is unknown; it is plausibly conjectured that the word is an arbitrary invention suggested by flabby of flap and aghast.
Aside:
If you want an old word English has "crapulous" which almost never used in its original meaning any more:
"Sickness caused by excessive eating or drinking."
Strangely enough in the Finnish language, which is completely alien to anything else European, the word "krapula" is in common usage for "hang over". Turns out to be old Latin/Greek.
OK, ok, I was working on the pretext of :- I am old, anything older than old must be anchient.
Getting even further off thread, I have been given an old Wharedale "Hi Fi" tuner amp, from the '70s. It has geranium transistors and most importantly a real variable cap, twin 300pF and triple 30pF ones (guessing). There is a steel chassis and a string tuning scale. I am a pig in muck (or whatever the Belgium or Finnish for that is)
I started designing another "Propeller Basic Module (V3.0)" including VGA and SD Card connections, taking the opportunity to get used to Eagle.
At the same time, I want to check the amount of disturbances in the VGA display when varying the distance between the Propeller and the VGA plug. So I am building a very small PCB with the resistors and some pin headers that I can plug either directly in the ide connector or on the flat ribbon.
I also tested the RS232 connection with the transistors and the following soft :
┌──────────────────────────
│ Parallax Serial Terminal Demo v1.0
│ Author: Jeff Martin
│ Copyright (c) 2009 Parallax Inc.
└──────────────────────────
Everything was perfect with the Parallax Serial Terminal (see the first photo).
But I also tried the Br@y++ Terminal because I used it with the Atmega and all the parameters can be configured. I was then surprised to receive extra characters (see the red arrows in the second photo) which I guess made the soft go to the next section (Pseudo-Random Number). Does anyone knows why ?
You are making great progress. It is always nice to see some serial data going through. Today I had a very exciting moment - I turned on a propeller board in my study, connected wirelessly to a propeller board outside, and wrote and ran a Basic program on that board outside. All the messages went via wireless packets.
I do not know the answer to your serial terminal problem - sorry. I have been using Teraterm and a serial port sniffer program. Very useful for debugging wireless packets where most of the bytes are not ascii characters.
I use Eagle a lot. I never found a library file for the ram chip, or the Propeller (they probably do exist) but a generic 32 and 40 pin chip work ok. I paid $125 to get the version that does a Eurocard size board. Some people use Kicad, and I think there are other good programs around.
When I will have the tests done with the distance of the VGA plug, I'll post the results on the forum. This will be a tiny contribution to the huge work already available to everyone.
I use Eagle a lot. I never found a library file for the ram chip, or the Propeller
I found one on the Eagle site. I think it comes from a guy of this Forum but I couldn't tell who (see the attached file).
Yesterday I discovered you are also active in the N8VEM group. Since a few months I receive the messages of the group in my mailbox because I own a few Z80 in a box, but for the moment I don't understand much of the messages. However I see there are ideas to combine a Z80 with 1 or 2 Props to replace the peripherals. Highly interesting. I hope one day my Z80's will be useful on a homemade PCB.
With regards to the lenth of conections to the VGA socket I have found that beyond the obvious "the shorter and most direct the better", I have used just single wires over 100mm to 200mm with a chasis socket. The wires had to be twisted together quite tightly to prevent picture degradations, but was ok for 640x480 etc. A lot of the cheaper (thin) VGA cables are just single wires in a common outer screening jacket.
(I had to buy a HDMI cable the other day. I looked the guy in the eye an told him that I wouldn't fall for the old £50 gold plated scam, so he tried a £40 one to start with (Bless). They even had a 3M one that would have cost more than the Blu Ray player. Eventually a £6 one was produced, with a warning " you will not get such good quality with this one"!!! It was only one Metre long, I told him that if the digits couldn't make it up that one I would be returning it along with the player as "unfit for purpose")
On the new PCB I will try to put the socket as close to the Prop as possible.
For the tests with the first PCB, the closest will be 3 cm + the length of 1 resistor.
The farest ( perhaps I should write "the most far" because my corrector tells me that "farest" is not correct) will be 3 cm + at least 25 cm flat ribbon + the length of 1 resistor.
I have a question. If I have a flat ribbon cable of 25 cm, with the first two connectors at 3 cm of each other connected to the Prop and the VGA plug (like on the photo 1), does it make any difference in the signal quality if I cut the queue off (like on the photo 2) ?
Sometimes it is difficult to tell that you are not primarily an English speaker, your English is pretty good.
Regarding your difficulty with "far", the proper term that you are looking for is: "farthest" - I know, it should be "farest", but the English language can be crazy sometimes. :shocked:
Thanks for your on-going commentary on this project. It looks really nice.
On the new PCB I will try to put the socket as close to the Prop as possible.
For the tests with the first PCB, the closest will be 3 cm + the length of 1 resistor.
The farest ( perhaps I should write "the most far" because my corrector tells me that "farest" is not correct) will be 3 cm + at least 25 cm flat ribbon + the length of 1 resistor.
I have a question. If I have a flat ribbon cable of 25 cm, with the first two connectors at 3 cm of each other connected to the Prop and the VGA plug (like on the photo 1), does it make any difference in the signal quality if I cut the queue off (like on the photo 2) ?
If the question is, "does the excess lenth of ribbon beyond the first take off point matter?" the the answer is probably yes. If I read you right then you want to source the VGA signal and put it into the end that has another connector not too far away. At this close connector you will take off the VGA signal, but of course the signal still has the lenth of ribbon between the closer connector and the farthest one. This will present itself as a simple capacitance, which shouldn't affect a 75 Ohm feed too much, but also as an unterminated stub. The signal will travel up this wire and just reflect off of the end, travel back to interfere with the wanted signal. However as this stub is very short in compareson to the sort of frequencies/wavelenths that travel, to even VGA ones, I wouldn't expect there to be a great problem, you might see ringing edges, such as black edges after white characters etc. The longer the stub the worse the effect onto the video would be, over 25cm or so I wouldn't worry too much and just see what happens.
Sometimes it is difficult to tell that you are not primarily an English speaker, your English is pretty good.
In 1978, I spent 2 years in New Zealand but I have lost a lot since then.
Regarding your difficulty with "far", the proper term that you are looking for is: "farthest" - I know, it should be "farest", but the English language can be crazy sometimes.
I think French language has a lot more exceptions than English. This makes the grammar very thick.
ESR stands for Effective Sieries Resistance, I suppose it is just another way of stating impedance rather than resistance. It measures at 100KHz, in this case, so an electolytic capacitor that is old and suspect will show up long before it changes its stated capacitance. It is invaluable for switched mode power supply work. It covers the range of 0-15 Ohms, a good cap, above a couple of uF, will be down in the very low Ohms. As they get tired then it creeps up to 10+ and becomes useless, also the internal heating gets higher and higher and it could split open.
On page 2 of the thread, the photos only show the top 1/6th of the image. Do you see the same? What is the status of the one sided prop board for hobbyists? Is it available or still being worked on?
Thing is you cannot talk of the "resistance" of a capacitor because it does not work for DC like an ideal resistor. We would hope the DC resistance of a capacitor is some lot of mega ohms.
However when AC is put through a capacitor current flows. This is determined by the capacitive impedance but also there are losses due to the resistance of the device leads and dielectric losses. So for AC the thing looks like a capacitor in series with a resistor. It's the value of that series resistor we are talking about with ESR.
In general all components have resistance, capacitance, and inductance, not to mention those fiendish capacitances to ground and other such parasitic effects. These cause high frequency electronic design to seem to be more like black magic than logic.
On page 2 of the thread, the photos only show the top 1/6th of the image. Do you see the same?
Yes I see the same. I think it comes from the fact that the 53 first posts of this thread have been copied from the old forum and for some reason the photos were not copied properly. You still can see the old thread here: http://forums.parallaxinc.com/forums/default.aspx?f=25&p=1&m=471919
What is the status of the one sided prop board for hobbyists? Is it available or still being worked on?
The board is finished and working. The last schematic and layout are here: http://forums.parallax.com/showpost.php?p=932540&postcount=88
Tle last photos of the real board are here: http://forums.parallax.com/showpost.php?p=931973&postcount=74
I am building a small circuit to test the influence of the distance on the quality of the VGA display because Toby and Dr_Acula made me conscious that SD Card and VGA plug had to be as close to the Prop as possible to avoid disturbances or even failure. I am also designing another version of the basic board including SD Card and VGA sockets. By the meantime I am learning Eagle. So it will take a while before I can put the new design on the forum.
Whilst planning for the ESR meter I tried messing about with TINA ( SHE would not be happy ).
I got the schematic in and tried to push it over into the PCB layout section. It then threw a wobbly on the ***168 footprint, even though it was in its library. Perhaps I will have to go the EAGLE route too, I think it allows for any angle of component rotations which would be useful.
Comments
Yes it is nothing else. It is not the latest version that Dr_A has produced, this was a MK2 (probably) and I think he has got up to MK5++ by now. It allows for the whole 512KB of ram to be accessed via its driver. The "Baby" double sided version I did only allows for 64KB of ram to had, but it was for Z80 anyway. It emulates at about 2MHz Z80 eqivalent.
Heater, Clusso, Dr_A and Pullmore were the movers of this, and other memory arangements, over the last couple of years. I chose the DracBlade variaty because it all runs on one Prop . This has now got to the stage of quite a few old clasics being emulated.
I am quite excited to come back from holidays and work to the layout of the board. I wonder if I can manage to find room for the VGA connector, the PS2 connector, the SD card socket, the memory, the latches and the 138 decoder. Fortunately, the Prop, the RS232, the power supply and the EEPROM are already on the first board.
I love watching a board being built this old-school way. The professional boards are fine, but they are very expensive if you only make a few, and it takes 10 days to get a board back. Single sided homebrew is something anyone can make themselves.
It is great watching Jean-Marie build this using tools we all have in the shed.
Is it possible to make the board bigger so everything fits? Or are you going to build this on lots of smaller boards and join them together?
I did find that the new high speed SD software didn't lik the added capacitance of a 40 way IDE connector, and that was only 50mm long. random single wires would be slightly better.
I came back a bit earlier from hollidays.
My first board is half the size of an euro board (thus 10 x 8 cm). I could use the full size (thus 10 x 16 cm ==> about 4 x 6.3 inches) if necessary. The most important thing is to put on one board the elements which have to stay always together. For example, the keyboard, the screen and the SD card can be thought to be always necessary.
I don't know if it would be more suitable to add the 512 K memory and the latches to the same board as the screen, keyboard, etc...or to put them on a separate board. Of course, it makes a difference. If everything is on the same board, there is no more free pin. So it becomes for example a problem to communicate with another controller. Indeed, not all utilizations need a large memory. I would like to have your opinion.
I hope this will not be the case with the soft of the Dracblade
That is an interesting comment from Toby about the extra capacitance and SD cards.
I can add my experience to that - I had one board design where there was more than 3cm between the propeller chip and the VGA socket, and the screen had a lot more noise on it. So my designs now start by making the propeller chip as close to the VGA socket as possible (ie just enough room for the resistors). I also move the resistors a little until the autorouter comes up with a solution that does not route the vga signals via long routes.
I am not sure about the ram chip. The greatest distance for a high speed wire (ie P0-P7) on my board is about 10cm.
I am using a standard eurocard for my boards. I do not have a strong view about one big board versus two smaller boards one above the other. There are advantages for both.
Re If everything is on the same board, there is no more free pin. So it becomes for example a problem to communicate with another controller.
There are two ways to communicate. One is to use the serial ports and this is what I am doing for radio links. 9600 baud is fast enough for me!
The second is to add extra chips. See the attached pdf. This is a design I have not built yet, but it adds 8 TTL outputs and 8 TTL inputs. See IC16 and IC5. You could then use those chips to build a high speed parallel interface - possibly up to megabytes per second.
I might just mention on that pdf the transistor at the top left corner that is part of the download circuit. The 'standard' circuit uses a 547, but this circuit uses a 557 and there is a pull up resistor rather than a pull down resistor. (any small signal transistor will do). This circuit is pullmoll's clever design and came about due to some timing problems with the BST program. The technical problem is whether the propeller resets on the positive edge or the negative edge. Rather than asking the author to tweak the timing of BST (which I think caused other problems), this circuit solves the problem for no extra cost.
There are lots of things on that schematic you might not need, and you can't use all of the features at the same time. It brings out the propeller data lines to a header. Analog I/O to another header. 2 more serial ports (I am going to use the board to build a serial router, which is something clever the propeller can do with existing software and doesn't need external ram). The mouse is added, but you have to choose between mouse and second serial port. Also leds for P0-P7 - for a simple 'blinkenlights' propeller demo.
I have tried to combine the prop demo board http://www.parallax.com/dl/docs/prod/prop/PropDemoDschem.pdf with the dracblade.
Maybe there are some ideas you can use?
With the older, and slower, SD software all seemed ok, but when some wizard came along, and made it so much faster, this setup started to show signs of distress in that most of the time it wouldn't boot up the DracBlade system. Strangely if the Prop was cold (freezer spray) then it would work, otherwise it would not. Cutting the traces on the bottom board, to P20-P23 allowed proper operation at all times. The other wiring to the memory always worked ok.
Either it was the extra capacitance of the traces and IDE40 Wire(50mm)_Plug/Socket assembly or it might have been the unterminated stub that that wiring had formed. If it was purely the capacitance then carefully parting the individual 40 wires from each other would cut down the capacitance a bit (and make it a bit more flexible).
I must also add that I managed to get a DracBlade running on my "Lunchbox", photos were put onto the DracBlade thread. This was effectively a DemoBoard(ish) PCB wired to a breadboard by long trailing wires, and then with lots and lots of long jumper wires. NB this was with the older SD driver. If the cct could survive that sort of abuse then hopefully there should be no problems.
http://forums.parallax.com/showthread.php?t=117996&highlight=dracblade (end of P19)
I had a warm and charming holiday with some tasty French wine which made me think of you.
Thanks for sharing your V8 schematic.
It'll not be possible to have less than 3 cm as I already have 2.7 cm on the first board between the pins of the Propeller and the ide connector. I must add to that a minimum of 1.3 cm flat ribbon and at least 2 cm for another ide connector and the resistors to the VGA socket. This makes a total of 6 cm.
Perhaps I should think over another layout for the base module, drawing my inspiration from your V5 or V8 schematic : I could keep together on the same PCB the Propeller, the EEPROM, the voltage regulators, the RS232, the VGA, the keyboard, the mouse/second serial port and the SD card and assemble on another board everything needed for the memory extension.
If Toby managed to build a Dracblade on a breadboard, I should manage to build one on 2 single side PCB.:rolleyes:
I was gob smacked, or whatever the equivilent in Belgium might be.
Could it be replaced by "It was mind-blowing" ?
I suppose that "Gosh, that is most suprising indeed" would have been more correct.
From the Oxford English Dictionary:
Aside:
If you want an old word English has "crapulous" which almost never used in its original meaning any more:
Strangely enough in the Finnish language, which is completely alien to anything else European, the word "krapula" is in common usage for "hang over". Turns out to be old Latin/Greek.
Getting even further off thread, I have been given an old Wharedale "Hi Fi" tuner amp, from the '70s. It has geranium transistors and most importantly a real variable cap, twin 300pF and triple 30pF ones (guessing). There is a steel chassis and a string tuning scale. I am a pig in muck (or whatever the Belgium or Finnish for that is)
At the same time, I want to check the amount of disturbances in the VGA display when varying the distance between the Propeller and the VGA plug. So I am building a very small PCB with the resistors and some pin headers that I can plug either directly in the ide connector or on the flat ribbon.
I also tested the RS232 connection with the transistors and the following soft :
│ Parallax Serial Terminal Demo v1.0
│ Author: Jeff Martin
│ Copyright (c) 2009 Parallax Inc.
└──────────────────────────
But I also tried the Br@y++ Terminal because I used it with the Atmega and all the parameters can be configured. I was then surprised to receive extra characters (see the red arrows in the second photo) which I guess made the soft go to the next section (Pseudo-Random Number). Does anyone knows why ?
I do not know the answer to your serial terminal problem - sorry. I have been using Teraterm and a serial port sniffer program. Very useful for debugging wireless packets where most of the bytes are not ascii characters.
I use Eagle a lot. I never found a library file for the ram chip, or the Propeller (they probably do exist) but a generic 32 and 40 pin chip work ok. I paid $125 to get the version that does a Eurocard size board. Some people use Kicad, and I think there are other good programs around.
When I will have the tests done with the distance of the VGA plug, I'll post the results on the forum. This will be a tiny contribution to the huge work already available to everyone.
I found one on the Eagle site. I think it comes from a guy of this Forum but I couldn't tell who (see the attached file).
Yesterday I discovered you are also active in the N8VEM group. Since a few months I receive the messages of the group in my mailbox because I own a few Z80 in a box, but for the moment I don't understand much of the messages. However I see there are ideas to combine a Z80 with 1 or 2 Props to replace the peripherals. Highly interesting. I hope one day my Z80's will be useful on a homemade PCB.
With regards to the lenth of conections to the VGA socket I have found that beyond the obvious "the shorter and most direct the better", I have used just single wires over 100mm to 200mm with a chasis socket. The wires had to be twisted together quite tightly to prevent picture degradations, but was ok for 640x480 etc. A lot of the cheaper (thin) VGA cables are just single wires in a common outer screening jacket.
(I had to buy a HDMI cable the other day. I looked the guy in the eye an told him that I wouldn't fall for the old £50 gold plated scam, so he tried a £40 one to start with (Bless). They even had a 3M one that would have cost more than the Blu Ray player. Eventually a £6 one was produced, with a warning " you will not get such good quality with this one"!!! It was only one Metre long, I told him that if the digits couldn't make it up that one I would be returning it along with the player as "unfit for purpose")
Thank you for sharing your experience.
On the new PCB I will try to put the socket as close to the Prop as possible.
For the tests with the first PCB, the closest will be 3 cm + the length of 1 resistor.
The farest ( perhaps I should write "the most far" because my corrector tells me that "farest" is not correct) will be 3 cm + at least 25 cm flat ribbon + the length of 1 resistor.
I have a question. If I have a flat ribbon cable of 25 cm, with the first two connectors at 3 cm of each other connected to the Prop and the VGA plug (like on the photo 1), does it make any difference in the signal quality if I cut the queue off (like on the photo 2) ?
Sometimes it is difficult to tell that you are not primarily an English speaker, your English is pretty good.
Regarding your difficulty with "far", the proper term that you are looking for is: "farthest" - I know, it should be "farest", but the English language can be crazy sometimes. :shocked:
Thanks for your on-going commentary on this project. It looks really nice.
Sorry I have been off-line for a bit.
If the question is, "does the excess lenth of ribbon beyond the first take off point matter?" the the answer is probably yes. If I read you right then you want to source the VGA signal and put it into the end that has another connector not too far away. At this close connector you will take off the VGA signal, but of course the signal still has the lenth of ribbon between the closer connector and the farthest one. This will present itself as a simple capacitance, which shouldn't affect a 75 Ohm feed too much, but also as an unterminated stub. The signal will travel up this wire and just reflect off of the end, travel back to interfere with the wanted signal. However as this stub is very short in compareson to the sort of frequencies/wavelenths that travel, to even VGA ones, I wouldn't expect there to be a great problem, you might see ringing edges, such as black edges after white characters etc. The longer the stub the worse the effect onto the video would be, over 25cm or so I wouldn't worry too much and just see what happens.
I think French language has a lot more exceptions than English. This makes the grammar very thick.
_____________________________________________________________________
Hello, Toby,
Thanks for your explanations. That's what I'm going to do.
Your PCB is very nice. But what is the verbose term for ESR ?
Humanoido
Not really impedance.
Thing is you cannot talk of the "resistance" of a capacitor because it does not work for DC like an ideal resistor. We would hope the DC resistance of a capacitor is some lot of mega ohms.
However when AC is put through a capacitor current flows. This is determined by the capacitive impedance but also there are losses due to the resistance of the device leads and dielectric losses. So for AC the thing looks like a capacitor in series with a resistor. It's the value of that series resistor we are talking about with ESR.
In general all components have resistance, capacitance, and inductance, not to mention those fiendish capacitances to ground and other such parasitic effects. These cause high frequency electronic design to seem to be more like black magic than logic.
http://en.wikipedia.org/wiki/Equivalent_series_resistance
It is now clear to me that ESR is a sort of Extra-Sensory-Resistance.
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Hello Humanoido
Yes I see the same. I think it comes from the fact that the 53 first posts of this thread have been copied from the old forum and for some reason the photos were not copied properly. You still can see the old thread here:
http://forums.parallaxinc.com/forums/default.aspx?f=25&p=1&m=471919
The board is finished and working. The last schematic and layout are here:
http://forums.parallax.com/showpost.php?p=932540&postcount=88
Tle last photos of the real board are here:
http://forums.parallax.com/showpost.php?p=931973&postcount=74
I am building a small circuit to test the influence of the distance on the quality of the VGA display because Toby and Dr_Acula made me conscious that SD Card and VGA plug had to be as close to the Prop as possible to avoid disturbances or even failure. I am also designing another version of the basic board including SD Card and VGA sockets. By the meantime I am learning Eagle. So it will take a while before I can put the new design on the forum.
I got the schematic in and tried to push it over into the PCB layout section. It then threw a wobbly on the ***168 footprint, even though it was in its library. Perhaps I will have to go the EAGLE route too, I think it allows for any angle of component rotations which would be useful.
http://cinco-series.blogspot.com/2008/12/photoshoot-tina-fey-30-rock-dans-vanity.html