Powering the VGA32

[Le Fauve]

Hi,

There has been quite a few posts about the VGA32 on this list lately (enough to make me order one :o) ) and I started a "portable tty project" around it.

That's a fancy name for a 7" LCD, a VGA32 and a few other things packaged in a 3D printed case, but I was wondering if it would be possible to power the VGA 32 directly, without using the micro USB port?

My LCD controller board has 5V available on a JST connector, and I've ordered a few male micro USB plugs, but I think it would be a lot more neat to power it directly "board to board" (also that would allow me to bring the USB port to the outside of the case so I can reprogram the VGA32 without having to disassemble everything).

Any idea how I could do this?

Cheers,

Eric

[Walt Perko]

Hi, 

I designed and made the .STL files available for FREE to house a TTGO VGA32 board along with a RS-232 to TTL board and power it from an external 5Vdc  ac adapter;  

https://pinshape.com/items/113511-3d-printed-vga32-fabgl-ttgo-ttl-to-rs-232-adapter-box

Now I have a KVM switch between this terminal and Gary Kaufman/Geoff Graham terminals for two of my computers:  Altair 8800c and an IMSAI ZPU computer so I can easily change to the display needed for the software.  

.

[Le Fauve]

Hi,

Thanks for sharing! This is a nice project, but I cannot see where you power the VGA32 from the pictures. Do you have schematics somewhere?

I suppose I cannot just use the battery connector, can I?

I happen to have the exact same TTL2RS232 adapter than you so I'll probably connect it the same way that you did (that will save me some headaches :o) ).

Cheers,

Eric

[Walt Perko]

Hi, 

I went to the thrift store and bought a bunch of cellphone chargers ... they put out 5V dc on the little USB connector.  That powers the whole thing.  Works great!  

.

[Le Fauve]

OK, thanks :o)

That's more or less what I'm doing at the moment, but I was looking for a way to NOT use the micro USB connector (like for example, on an Arduino board, you can power it with the USB port or you can connect directly to Vin/GND pins).

There are not a lot of extra pins on the VGA32 but I was hoping there was an "easy to solder" spot where I could connect my power supply.

[Walt Perko]

Hi, 

I have mine all glued into their little boxes, so I can't do the test, but try a DMM from GND being the metal shell on the microUSB port to those IO PIN holes next to it.  IF any one of those PINs is 5V and you're not using it for something else, you can power the board there.  A simple continuity check to other points you can find a GND attachment instead of the microUSB port shell.  

It wouldn't hurt to publish the results here when you find good GND and +5V pads.  

.

[Tom Lake]

"Connecting to the Altair pro can be tricky if your ports are all in use you will need to hack in the txl/rxl mod to the aurdino due giving you another serial port"

or you can add as many RS-232 serial boards as you have open slots if you have a backplane. The Pro has five internal slots and in my system one is taken up by an extension connector that connects to a 25-pin D-shell connector mounted on the back of the Pro..

Externally I have a six-slot backplane connected by a short cable from its 25-pin D-shell connector to the 25-pin connector on the back of my Pro.

This gives me a total of ten slots and I have eight add-on boards (one of each kind, so far) so there are two unused slots. I could use one of those slots to daisy-chain to another backplane but until there are enough boards available to warrant doing that, I won't. Since the bus card serial ports can't generate interrupts, they can't be used with Timesharing BASIC which would be my main use for them.

On Tuesday, December 27, 2022 at 2:41:17 AM UTC-5 John Galt wrote:

On the latest vga32 pcb there is a 2 pin white plug next to the micro usb I believe that is 5 volts in however documentation  is Terrible. 

If you want to be safe use the micro usb and splice power into it from your lcd power so you can use one power supply.

I don’t know the power requirements of the vga32 I’m using a 2.5amp supply I took from my raspberry pi I’m running a crt monitor so I need the power for the crt and the vga32 separated.

I know the vga32 can be supplied from a shared source since it was designed for the z80 home brew computer

The vga32 will greatly increase what you can do with any computer requiring a terminal it gives you mouse support and 64 color display 4 colors per channel plus it emulates many different terminals and you can add your own terminal definitions additionally you get cursor key support which was designed to work with wordstar making it much easier to use. There are additional stls available on thingiverse for the esp32 

I have a few esp32/vga32s setup as computer emulators a ibm 5150 and terminal emulators.

Connecting to the Altair pro can be tricky if your ports are all in use you will need to hack in the txl/rxl mod to the aurdino due giving you another serial port otherwise you need a master usb board since all the micro USB ports on the due are slaves. After trying that route it works much better connected to the port b 9 pin or the txl/rxl mod

I have a ton of hardware devices connected to my Altair pro so I was full up

[villa...@gmail.com]

the VGA32 power is not easy to get at if you wish to bypass the USB connector. The +5v doesn't come out on the 8pin plug/socket, only 3.3v available there. Presumably it's on the PS2 connectors but I've never fed 5v IN via this route!!!!

Here's the link to the schematic which may make life easier !!  https://github.com/LilyGO/FabGL/blob/master/Schematic/vga32_v1.4.pdf

[Walt Perko]

Hi, 

It's right in the middle of that schematic ... the little white 2-PIN connector is the power IN for the board.  Find the part number for that ... you might even find a little cable with the Male connector and a 5.5/2.5 dc jack.  Post that info here and I can add another port onto the little box I made for the TTGO VGA32.  

.

[Le Fauve]

Thanks for the feedback!

John, r4guy, I think the white JST connector is for a battery. I don't think it's safe to power the VGA32 from this connector since it probably expects something like 3.7V and also, while the USB is connected it's likely that the TP4054 will try to charge the battery; I'm not sure how that will go if I'm powering it at the same time.

Tom, I have a pretty old altairduino (bought it in 2018) so I'm not sure of the model, but it's definitely not a "pro" (it came with a bamboo case, and I had to print my own back panel for some reason (I don't remember why)).

I like the extension bus I've read about on this group, but I'm not sure my particular altairduino can support it (can it?).

I do have a max3232 module, though, so it shouldn't be too hard to connect a serial terminal.

Villa, thanks for the schematics! :o) That will be very helpful.

I didn't consider using a PS/2 port for power but that may actually work. I'm considering removing one of them anyways to replace it with a RJ11 plug (for a WY30 keyboard) so it won't be too difficult to feed 5V in there. I'll double check first that the 5V rail is directly connected between the PS/2 ports and the USB port.

I'm waiting for some parts to be delivered (mostly JST connectors to tidy everything up), but here is a picture of the unfinished project to give you an idea of what I'm trying to get:

From left to right: The VGA32, the LCD controller, the (still not fixed) max3232 and the buttons board for the LCD controller (the LCD panel is on the other side).

I still need to add an audio amplifier and a couple of speakers, a RJ11 for my keyboard and I'll try to add a CH376S so I can plug USB drives.

Cheers,

Eric

[Walt Perko]

Hi, 

Nice looking print!  On the schematic, it shows the white connector as being 5V and GND IN ... that's exactly what you want and you can power the RS-232 to TTL board with the same 5V IN as I did using a 2-1 Dupont jumper wire.  

.

[Tom Lake]

If your AD doesn't have its own backplane, then you can still wire up a connection by running wires from the relevant Arduino pins to a DB-25 connector and then run a cable from that to an external backplane. You'd have to change at least one value in the Arduino sketch and recompile it to allow use of the backplane.

Mandatory change:

line 92 of config.h
Change:

#define USE_IO_BUS 0

to:

#define USE_IO_BUS 1

Optional changes (depending on which bus cards you have)

In order to use real floppies, I also turn off throttling altogether by changing line 37:

Change:

#define USE_THROTTLE 1

to:

#define USE_THROTTLE 0

Throttling can be turned off in the configuration but since I'll never be using my AD without the bus cards, 

I don't even want to see the option and have any chance it can be changed inadvertently.

Since I'll always be using the Centronics bus card, I also save about 140 bytes of RAM by turning off printer emulation in line 69:

Change:

#define USE_PRINTER 1

to:

#define USE_PRINTER 0

[Brian Welland]

Hi,

Following from Tom's comments we also had an older AD in its bamboo box (almost exactly what you have) and converted this using an adapter as detailed in the attachment.

A few others have used this technique which enables you to easily convert your AD back if necessary.

The 25 way connector fits on the back panel of the bamboo box and thus IMHO makes this simple conversion neat and tidy.

The hard bit is getting the IO bus active and working but if you recompile as per Tom's comments then you are most of the way there.

Have fun.

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[Tom Lake]

That's a cool little device! I never knew it existed. That makes adding a backplane so much easier and reliable than running individual wires.

[Le Fauve]

On Thursday, December 29, 2022 at 9:08:13 PM UTC+10 r4r...@gmail.com wrote:

Nice looking print!  On the schematic, it shows the white connector as being 5V and GND IN ... that's exactly what you want and you can power the RS-232 to TTL board with the same 5V IN as I did using a 2-1 Dupont jumper wire.  

Thanks r4rguy, but I really cannot see on the schematics where you can tell the white connector is connected to 5V.

From what I see ("BATTERY" schematic in the middle of first page), it's connected to GND for one pin, and vbat for the second (and io35 via a voltage divider probably to read the battery current voltage).

Also I think the MAX3232 should be powered with vbus (3.3V) and not by 5V if you want the Rx pin to be at 3.3V level.

I also have another question: Looking at the schematics, it seems we can connect a speaker, but I really cannot tell where (the weird thing is... it really looks like pins 5 and 8 of the NS4150C (3W mono audio amplifier) goes to... the 3 pins white connector).

Now I'm wondering if the battery connector isn't the unpopulated pads on the back of the micro-sd card reader (that would explain why the battery connector on the schematics has pins instead of two).

Any thought?

Eric

[Le Fauve]

Tom and Brian, thanks a lot for the information about the mod to add the IO bus!

That will probably my next project as soon as I manage to get the whole VGA32 thing working :o)

I had a quick look at the PDF, but I'm not very sure where you're supposed to connect the DB25?

Is there any other documentation telling me which of the Due pins I need to connect?

I suppose things will be a little clearer once I got the protoshield in hand.

Cheers,

Eric

[Walt Perko]

Hi, 

In the center of the top section of the schematic you can see the battery section.  On the right side is the PH-2-WO or P1 connector.  PIN 2 is 6V d.c. IN ... PIN 1 is GND, so I would expect that you can power the board with a 6V a.c. wall-wart adapter.  

However, I powered both my TTGO board and the RS-232 to TTL adapter from a 5V d.c. wall-wart adapter plugged into the USB port.  

It's easy to unplug the USB cable from the a.c. adapter to plug it into the USB port on my PC if needed, but unless somebody comes up with better terminal firmware than the current released version, I don't expect to need the USB port.  

.

[villa...@gmail.com]

I power my VGA32 from the USB socket, but an alternative perhaps could be to feed the power source into a USB breakout board, break open a usb cable and feed that to the breakout board and into the VGA32, you also now have access to the +5v and ground at the breakout board for a 232 convertor. As Eric pointed out the Rx should be a 3.3 v signal to the VGA32 so I use a 2.2k / 1K resistor divider  (if it was a 5v signal). This works perfectly.  I use the audio socket to feed into a small amplifier, sound quality not brilliant but works!!!
Clin

[Le Fauve]

On Tuesday, January 3, 2023 at 10:53:48 AM UTC+10 r4r...@gmail.com wrote:

In the center of the top section of the schematic you can see the battery section.  On the right side is the PH-2-WO or P1 connector.  PIN 2 is 6V d.c. IN ... PIN 1 is GND, so I would expect that you can power the board with a 6V a.c. wall-wart adapter.  

I see two issues:

• P1 is probably not the white connector (it has 4 pins, the white one has only two, also its two pins seems to be connected to the audio amplifier's outputs)

• When you connect the micro-usb, the TP4054 could try charging the battery, and send power into your power supply (it shouldn't if it think the battery is already full, but I don't know enough about batteries and charging controllers to bet on this.

Also I realized it would be easy to check if the white connector was actually a speaker connector. I connected an oscilloscope and... yes, I can see the (very badly rendered but totally recognizable) waveforms.

Also when I plug a headset, the signal to the speaker disappears, which is normal according to the schematics.

And lastly, I connected a speaker and it does work :o)

Bottom line: DO NOT CONNECT power to this white connector!

[Le Fauve]

On Tuesday, January 3, 2023 at 7:40:22 PM UTC+10 villa...@gmail.com wrote:

I power my VGA32 from the USB socket, but an alternative perhaps could be to feed the power source into a USB breakout board, break open a usb cable and feed that to the breakout board and into the VGA32, you also now have access to the +5v and ground at the breakout board for a 232 convertor. As Eric pointed out the Rx should be a 3.3 v signal to the VGA32 so I use a 2.2k / 1K resistor divider  (if it was a 5v signal). This works perfectly.  I use the audio socket to feed into a small amplifier, sound quality not brilliant but works!!!
Clin

Thanks Clin!

That's more or less what I'm planning. I ordered a lifetime supply of male microUSB connectors (I could have order 20 for $3... or 100 for $6; I choose the later ;o) ) and I'll do my connections using the microUSB port.

I think I'll try something like:

- Having a female USB port for power and/or programming

- The power from the female USB goes to power the LCD controller, from which a 5V output goes to the VGA32 via the 2 power lines of the microUSB

- The 3 other lines of the female USB go directly to the microUSB

This way, I hope I can either power the whole assembly, or program the VGA32 when needed.

For the 232 connector, if yours is using a MAX3232 chip, you should be able to directly power it with 3.3V (it accepts anything between 3V and 5.5V). Doing so should ensure that the Dx signal will stay in the 3.3V logic range.

I say "should" because according to the datasheet, the charge pump capacitors should be different when the Vcc is 3.3V and when it's 5V so unless you do know which capacitor values are installed on your adapter you'll have to check and try (if it works fine with your divider bridge, it probably doesn't worth changing this, though).

For the speaker, I was planning to do exactly like you (adding an amplifier and a speaker to the headset connector) but since I found out there was an audio amplifier on the board, I just connected a speaker to the white connector.

Here is a quick demo: https://youtu.be/db556S3GUio

And thanks again for the link to the schematics! It really made my life easier! :o)

Cheers,

Eric

PS: Here are some links to the parts I've ordered:

- The connector I used for the speaker in case you guys want to go down this road: https://www.aliexpress.com/item/33009614944.html (you need the "2P" one)

- The microUSB male connectors I plan to use (I suspect they will be painful to solder to, so you may prefer a more classic microUSB breakboard) : https://www.aliexpress.com/item/32991989951.html (I choose the "5P" ones, but the "2P" may be easier to solder if you just want the power lines)

[Walt Perko]

Hi, 

I'm wondering if you can post a photo of the VGA32 board you are using?  My board has an Audio out connector on it, and I just plugged a pair of cheap powered PC speakers so I can adjust the volume.  

The Audio OUT is the black 'n brass connector on the board I'm using.  

.

[Walt Perko]

Hi, 

I may have found the published Tektronix version:  https://forum.classic-computing.de/index.php?attachment/96928-fabgl-tektronix-zip  

I'm busy working on a music program so I'm not ready to try making changes to my terminal for now, but if this is a working system, please let us all know.  

,

On Tuesday, January 3, 2023 at 11:57:52 AM UTC-8 John Galt wrote:

here is a document on a the Ver 1.2 of the ESP32 board 

https://docplayer.net/191008555-A-graphics-terminal-with-ttgo-vga32.html

It does mention the white 2 pin connector is for a battery.

1.2.

Power Connectors

Two connectors can be used to provide power:



a

Micro USB connector can be used to plug

in a

common 5V USB power supply,



a

small two pin connector can be used to connect to a 3,6V

Lithium

-

Polymer

battery

the person that wrote the document also extended the terminal to run Tektronix escape codes.

but they never published the modification.

[Le Fauve]

On Wednesday, January 4, 2023 at 5:07:32 AM UTC+10 r4r...@gmail.com wrote:

> I'm wondering if you can post a photo of the VGA32 board you are using?  My board has an Audio out connector on it, and I just plugged a pair of cheap powered PC speakers so I can adjust the volume.  

> The Audio OUT is the black 'n brass connector on the board I'm using. 

I'm using the exact same board than you. What you call "Audio OUT" is a "Line out" output. It's connected directly (if you except a few passive components) to IO25 which is used to generate sound signals.

This "Line out" signal isn't amplified at all, and will be usable with a headset or amplified speakers (note that while the connector is stereo, there is only one channel of audio generated, and it is connected on both Left and Right channels of the 3.5mm jack connector).

Now if you continue to look into the schematics, you can see that when nothing is inserted in the "Line out" jack, the audio signal is forwarded to a 3W audio amplifier (the NS4150 chip) and from there, an amplified signal is sent to the little white connector.

On the document posted by John ( https://docplayer.net/191008555-A-graphics-terminal-with-ttgo-vga32.html ) , you can see on Figure 4 that a speaker is connected to this exact same white connector.

If you look on next page, there is a picture which shows the battery connector (a second 2 pins white connector, but of a different kind). While the connector has only 2 pins, it does use a 4 pads footprint on the PCB, and if you look closely, you can see that this footprint is the exact same than the one which is on top of the "BAT_TEST-35" marking on your picture.

I just suppose that very few peoples were using the VGA32 with a battery, and as a cost saving measure they decided to not include the connector on the rev 1.4 of the board.

On Wednesday, January 4, 2023 at 5:57:52 AM UTC+10 John Galt wrote:

> here is a document on a the Ver 1.2 of the ESP32 board 

> https://docplayer.net/191008555-A-graphics-terminal-with-ttgo-vga32.html

Thanks John! Not only this document solved the mystery of the battery/speaker connector, but I really like the idea of adding Tektronix graphics supports to my terminal.

The original reason I choose the VGA32 is that it has an open source terminal emulation software, on a platform I can easily patch for adding new features.

What I really wanted is a VT100 like terminal with full support of sixel and ReGIS graphics. I'm not sure that's the case of the FabGL terminal, but I'm planning to add those support if they are missing.

Now, I'm just waiting for the postman to bring the next batch of pieces so I can continue the hardware part.

Cheers,

Eric