www.megadrum.info

I've already emailed Dmitri on this but wondering if anyone else has input as I don't want to repeat my mistake. My goal is to build-out a Megadrum unit with a handheld controller enclosure, and everything else in the main enclosure that will be shock-mounted into the bass drum (and drums) I wear on my back. See http://www.marcdobson.com for video and pics.

I blew up the LCD 16x2 output on my MegaDrum (main board with ARM STM32F205RCT6 at 120MHz). By blew up, I mean I can no longer see anything useful except full blocks of pixels on the top row and nothing on the bottom row. The unit still does trigger midi and the MegaDrum Manager FX appears to continue to work properly. BUT I am not experienced yet running Megadrum so I've not tested every function.

All components of my Full Megadrum kit worked pre the following.

Blow out happened after I extended the 16 LCD lines through a 30" DB25 cable, two DB25 connectors, and 4" to 6" of cable. I tested this, leaving power on for about 10 minutes and figured the extension worked. Then, I hooked up my 4 button keys (not from DIY Megadrum kit) and diodes on a breadboard which initially did not work. I did change the orientation of key pins thinking I may have had it backwards. Then I noticed the ground pin in the key row had no solder on it (backside) and freely slide through the board, so I added some solder. At this point I should have checked grounds for continuity but did not Then on the 4th or 5th try (1st try after solder), the left Key worked, and I noted it worked the same as turning the right rotary. I've not been able to turn my LCD screen on (long enough) to confirm what the left button does from the initial screen. Then, I pressed the up or down key and I got this "death row of boxes".

I powered off and on a few times. One or two times, MegaDrum initialized properly then returned to this "death row of boxes", sometimes a garbled set of characters appeared.

Then, I tried the rotary buttons that came with my kit.
Then, I downloaded MegadrumManager FX and connected no issue.
I updated to the latest firmware 20190602. The screen flickered but "death row of boxes" prevailed.
Then, I rolled back to firmware 20181218 and the unit initialed but within 5 minutes returned to "death row of boxes".
With a nervous twitch in between other tasks, I've tried to power it up, too many times.

I ordered a 1.8 TFT Color Display from Amazon and that would not even light up (I did jump pins 13 and 14 on LCD).

So here's what could have gone wrong:

- Incorrectly connected buttons.
- The long run of wire to LCD, when in use/keys being pressed was the failure.
- I did not shield the ends of wire where they attach to connection cups of DB25 connectors. I've google searched that image and have not found anyone to leave them bare BUT I carefully inspected all my solder joints before proceeding and everything looked good. NOTE this is my 1st real electronics project besides maintaining my own gear for 30 years.

AND Dimitri's email response was:

As far I know it is impossible to damage the main board by connecting the buttons incorrectly - I've incorrectly connected buttons (and encoders for that matter) to my test boards countless times.
The buttons pins on the main board are input pins and connected buttons cannot feed any unwanted voltage/current whichever way you connect them. On the other hand, connecting the LCD incorrectly can cause damage to the board. Btw, as far as I remember you are the first to have a problem with a kit.

I don't want to blow up another board and have to decide if I should try the extension again, in another safer way OR mount the mainboard in my controller enclosure (which I want to fit into a pocket on my chest). The enclosure in the bass drum would have drum pad, midi and maybe power connections. The midi out will go to an iTouch running Sample Tank and audio out of iTouch wireless back to my PA rack. Part of my goal with this is to go from my current set of 4 wireless transmitters (trigger kick, trigger snare, mic on crash and mic on Hi Hat) to 1 wireless transmitter for all drums.

It's hard to tell what the issue might be, but I've also wrongly connected loads of stuff, including plugging in the LCD connector the wrong way, and have never managed to damage anything. I'd say there might be a loose connection somewhere between the LCD and the board. Check for continuity between the solder pads on the LCD and the end of the connector going to the board. You could also try with another LCD - they're cheap so not really a big gamble.

It's hard to tell what the issue might be, but I've also wrongly connected loads of stuff, including plugging in the LCD connector the wrong way, and have never managed to damage anything. I'd say there might be a loose connection somewhere between the LCD and the board. Check for continuity between the solder pads on the LCD and the end of the connector going to the board. You could also try with another LCD - they're cheap so not really a big gamble.

Thanks, ignotus,

I've plugged in an LCD upside down too, a couple of times and never had damage.

I forgot a couple of points:

• Already tried another LCD (almost exact same) and confirmed the problem is on MegaDrum board. Other LCD shows the same screen when plugged into MegaDrum. LCD that came with MegaDrum, when plugged into Arduino Kit (that my other LCD came with) works fine.
• I inspected and cleaned MegaDrum with alcohol and cotton swabs.
• I forgot to mention, from this thread of related but not exact same LCD problem https://www.microchip.com/forums/m/tm.aspx?m=854551&p=1
  ...one poster said this:
  

  One row of boxes at the top of a two-line display almost always indicates either bad initialization or a data or control wiring fault and is because the display controller is still in its power-up default of single-line mode which needs a different contrast voltage to two-line mode.

• I have already ordered a second MegaDrum Kit from Dimitri. I will do some comparison continuity tests but I'm hesitant about trying an extension again.

I want to try extension again and sheild all the ends of the DB25 connectors BUT I don't want want to kill another component.

Test continuity from LCD pins to the pins of STM32 chip.

Test continuity from LCD pins to the pins of STM32 chip.

Tested, and got continuity from all LCD pins to pins of STM32 chip, as on schematic, including pin three with 220 Ohms of resistance which has an inline R9 220 resistor.

If I would have noticed 7 of the 16 LCD pins go to ground before making that extension, I would have saved some time before the "death row of boxes".

I've conversed about this with members of my Maker Space and their opinion is, I must have shorted out one of the pins. I will get another STM32 for this board. When time permits and hopefully with guidance from a maker space member, I'll replace the chip. This currently seems daunting as I've just started to wear reading glasses for working this stuff It seems I can get a STM32 for less than $10. This board will then go into a backup position and as a working board for a 2nd backpack drum kit I intend to build.

Before I move forward, I'm going to wire a 16x2 LCD to something cheap and disposable. I will heat shrink the ends of DB25 cup connectors and test for continuity and shorts before I connect.

Too bad the LCD can't be run on IC2, with just 4 wires.

If I can't run an extension on the LCD, I'm thinking about my options. I could:

a) Put mainboard, LCD, buttons, LED and maybe power switch in this controller enclosure box I want to sit in a front pocket position. Pad connectors, midi, and power jack will go in an enclosure mounted in my backpack.
b) I put everything in one enclosure BUT build with enough wiring slack, so that I can have it on my front to make adjustments and once close, mount it in the backpack. I'll have no control on the fly directly to the device, however...
c) In addition to c) I gain control to MegaDrum over an iTouch, which will also be the sound module. I've not yet tried, but I have the MIDI Designer ap which can be extensively customized to control everything MIDI.

Thanks again for input

Buying a new STM32 won't be any use because it won't have the bootloader programmed on it - it will be a blank chip that you can't load the firmware to. Besides, it'd be a nightmare to desolder the old one and replace it without shorts - not a trivial task. What about giving the 1.8" TFT another go? Are you sure it's the same model as the one described in the manual?

ignotus,

Aha, thanks for heads up, I did not realize it's a "protected boot loader".

Besides, it'd be a nightmare to desolder the old one and replace it without shorts - not a trivial task.

I agree, perceived as a nightmare. I watched a how-to YouTube video last night, it's a lengthy process and it's key to check for shorts after install. BUT a couple of the members at my MakerSpace do this work frequently and we might (and might not) do a "how to replace a microprocessor class". BUT that will depend on if I can get another STM32 with bootloader.

What about giving the 1.8" TFT another go? Are you sure it's the same model as the one described in the manual?

Yes, I'm going to give that another go and I'm not 100% sure about the 1.8" TFT I got, off Amazon. It looks identical to the one in MegaDrum Manual, however... I got no power to it when hooked to MegaDrum. I did get power but no useful display when hooked to my Arduino Mega after many test codes and libraries. After a good search, I found there are cheap Chinese versions of these TFT's that are not spec'd correctly by sellers, so... when I have the time I will test the 1.8" TFT I have again on another device and/or will buy/borrow and try another (one of three) color display options we have. Even though fairly cheap, hopefully, I'll have an alternate use for another display I'll buy if the test does not work out.


Dimitri,
I've read through https://www.megadrum.info/content/progr ... m_firmware
detailing Getting Atmega with protected bootloader: with posting dates of 2007 thru 2010

I'm not in a rush but would it be possible to get an STM32 with bootloader programmed from you, or the source listed on the forum?

I've bought several cheap TFT screens off of Aliexpress and they've all worked, but I suppose some turn out to be duds. Yeah, having an Arduino is a handy alternative to see if they're working, but IIRC I think I did have a few headaches getting them to work with that too, particularly with the Arduino Mega - I found a several conflicting instructions on how to wire them.

Did you try the LCD with the Arduino?

I believe, with the 1.8" TFT I bought, ... from many forum posts, some are misrepresented as 5v / 3.3 v when they are really just 3.3v and need resistors in order to properly work, which I tried.

https://www.amazon.com/gp/product/B07BF ... UTF8&psc=1

I've too found many conflicting wiring instructions with this LCD and other components for the Arduino Mega, but at the moment the Mega is all I have.

I have other upcoming projects which are better suited for Arduino uno or nano. Once I make those purchase decisions, I'll then try the LCD there too.

As I suggested over e-mail, you can send the board back to me for troubleshooting.