New ARM based MegaDrum.

[dmitri]

Hi Dmitri,

regarding the connectors we perhaps misunderstood. Can I replace the ATmega board by the ARM board without changing my existing cable harness? If not, what has to be changed?

Yes, you can replace the Atmega board with the ARM board. The pinouts of USB/pads/LCD/encoders/buttons/LED/MIDI connectors are the same. The ARM board is slightly smaller and 4 mounting holes on the board are spaced slightly differently so if you want to replace the Atmega board with ARM board then you have to drill 4 other holes in a case for mounting.

To understand the changes with the result of better latency with the STM32some statements and questions:

The STM32 has 3 ADCs with 1us conversion time at 56MHz or 1,1us at 72Mhz in comparison to the ATmega has only 1 ADC with 13 us conversion time. Did you use all 3 ADCs of the STM32? Fast interleaved mode?

The STM32 has an DMA function on the ADC. Did you use it or do you read the ADCs by interrupt or daisy chain?

I do use extra functionality in STM32:)

The ADC of the STM32 has two bits more resolution. Did you enhance the some functions for example the custom trigger curves?

I do use 12 bit mode but it is not used for any enhancements at the time.

[chrishopf]

Hi Dmitri,
thank you for your answers.

My questions regarding to the ADC do not target to get secrets from you. I am not in the situation to construct my own trigger. I have not much time for it.

My aim is to help you and all the community to enhance this project. I am also an engineer in electronics but not any more in the design department (now purchasing), but I am close to the information sources regarding the microcontrollers. I know design engineers who are designing since three years on this controller family. I also have direct contact to STMicroelectronics.

So, do not hesitate to contact me, if you need a second opinion. You can send me an PM if you like.

Christian

[dmitri]

A limited offer:

I have 4 STM32F103RBT6 chips which I bought for development. The only practical difference STM32F103RBT6 has in comparison with STM32F103RCT6 is 128Kb vs 256Kb Flash ROM. This makes very small, if at all, real difference since the current MegaDrum firmware uses ~70Kb and it won't grow over 90Kb in foreseeable future.
With each new firmware release I will provide STM32F103RBT6 version along with STM32F103RCT6 version.

So I offer 4 STM32F103RBT6 based boards for 100GBP plus shipping whereas regular STM32F103RCT6 boards are 110GBP plus shipping. And of course 15% discount for anyone who bought kits/modules in the past still applies. Once gone - they're gone, I will keep only one board with STM32F103RBT6 for myself for development/testing/support purposes.

[dmitri]

three STM32F103RBT6 based boards left.

[angr77]

First impressions on the nice ARM based MegaDRUM.

Got my board yesterday....looks really neat! No problems to install, drilling new pin outs. Just to boot up! I had some small problems with the right AltEncoder...which has been solved in a later firmware. Otherwise...If you are familiar to the AtMega 1284...no surprises here. Midi-speed selector in firmware is gone...The ARM board uses standard MIDI speed 31250 for midi and for USB MIDI it uses Full speed USB (12Mbit).

When upgrading the firmware - the selection of CPU speed is gone...it is always 72 MHz. One question appeared, should I use the megadrumSTM32a_56 or the megadrumSTM32b_56 firmware file? But it was only to read on the LCD display which version I had...The A-version board is for the 128 KB version and the B-version board is for 256KB version.

When the MD was up and running against MDM, the midi-function operates just a as usual. I have updated the MD settings with a backup from the old board stored in a MDS-file for my drumset - the same configuration file can be used as for the AtMega 1284 board. However, some readjustments is needed for the settings since the values between Atmega and ARM boards don't match exactly.

I just played around with my VH-11 hi-hat and had to do a new EdgeswAll sequence before TIP/Edge and Choke was working as usual again. The Piezo based drumpads was working right out of the box using my old configuration.

Feeling: Maybe too early to tell...but I am definitely noticing a faster handling of the midi data and functions like the hi-hat pedal.

So - I am going to do a rehearsal with the band tonight...super excited how well the ARM based board can operate and perform for an old lousy drummer…It feels like X-mas already!

Anders

[Cysign]

I'm really impressed by you using an ARM core.

Do you have any plans to build your own soundmodule since ARM cores gain more power and now your familiar with it? Maybe based on Android.

Or maybe an I/0-board for Raspberry Pi would be interesting. By using an array of Raspberry PIs connected by those GPIO-ports there could be (nearly) unlimited polyphony by adding more units

Btw: What would it cost to switch from Atmega to ARM? Couldn't find any info about the pricing...

[dmitri]

I'm really impressed by you using an ARM core.

Do you have any plans to build your own soundmodule since ARM cores gain more power and now your familiar with it? Maybe based on Android.

Or maybe an I/0-board for Raspberry Pi would be interesting. By using an array of Raspberry PIs connected by those GPIO-ports there could be (nearly) unlimited polyphony by adding more units

I believe it's better to be done by an external device - a PC/tablet/phone.

Btw: What would it cost to switch from Atmega to ARM? Couldn't find any info about the pricing...

It's in the first post:

3. Everyone, who ordered Atmega based kits/modules in the past, will get a 15% discount when ordering ARM based kits/modules.

Costs for relevant modules and kits (including a stand alone board) can be seen in relevant topics.

[Cysign]

I'm really impressed by you using an ARM core.

Do you have any plans to build your own soundmodule since ARM cores gain more power and now your familiar with it? Maybe based on Android.

Or maybe an I/0-board for Raspberry Pi would be interesting. By using an array of Raspberry PIs connected by those GPIO-ports there could be (nearly) unlimited polyphony by adding more units

I believe it's better to be done by an external device - a PC/tablet/phone.

That an Raspberry Pi is. It's a mini-PC using an ARM core at 1Ghz, 512MB Ram and running with Raspbian, an Wheezy-Debian compiled for ARM-architecture.
But as it provides GPIO-ports maybe it's intresting to use it as very compact soundmachine. But in case it doesn't have enough power, an array of a few PIs could handle that big ammount of needed performance.

As an Raspberry Pi is about 30$ it's really cheap and everybody could afford it and - if neccessary - enhance it by others.

I tprovides an 3.5mm sound output, LAN connector and two USB ports beside those GPIO-ports which could be interesting for realtimecontrol.
When using multiple PIs there's an mini-mixer needed to mix all those outputs together. But that shouldn't be a big deal.
http://www.raspberrypi.org/

As it's using an SD-card instead of an HDD it's not fragile. And as it is using an standard 5V 700mA powersource (maybe an phone charger with micro-USB-jack) it's ultra portable. But as I'm not a programmer I'm not sure it it's performance would be enough for a sound-libary. A single-device for sure would be too slow to handle all those polyphonic sounds.

[dmitri]

It's not the cost of the sound device, in your example of a Raspberry Pi, which is a main obstacle. The main obstacle is to write a low latency high quality sound synthesizer with a high quality sound library.

[everson]

Do you think we can see something like that out of Megadrum in the near future?
Do you have plans to make something like this?