I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

awneil — Mon, 18 Feb 2019 10:31:19 GMT

[quote userid="14926" url="~/f/nordic-q-a/37567/i-am-trying-to-do-dmx512-protocol-i-hope-to-help-me-time-is-very-urgent/171586"]you need to create your own custom board[/quote]

Or look for a 3rd-party board with an nRF52810 - there are some module makers with nRF52810-based modules ...

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

Jørgen Holmefjord — Mon, 18 Feb 2019 10:20:27 GMT

Unfortunately, this is one of the very few things where the features in nRF52810 is actually improved compared to nRF52832. If you want to evaluate larger MAXCNT registers, you need to create your own custom board or use the nRF52840 DK. This is a hardware limitation on nRF52832 and it is not something that can be emulated.

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

awneil — Sat, 16 Feb 2019 10:02:50 GMT

The nRF52810 is a cut-down subset of the nRF52832.

Nordic don't have any Dev Kit for the nRF52810 - so this "emulated" business is just about letting you do development on the nRF52832 DK and "pretending" the chip is an nRF52810

See https://devzone.nordicsemi.com/f/nordic-q-a/33812/developing-for-nrf52810---the-full-story

EDIT

But see Jørgen Holmefjord's comment below about MAXCNT on the nRF52810

EDIT 2

There is a list of the limitations in the linked article:

http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v14.1.0/nrf52810_user_guide.html?cp=4_0_3_5_0_1_0#ug_52810_limitations

and in the new Doc Lib:

https://www.nordicsemi.com/DocLib/Content/SDK_Doc/nRF5_SDK/v15-2-0/nrf52810_user_guide#ug_52810_limitations

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

Alan — Fri, 15 Feb 2019 23:11:13 GMT

My mistake, I should have asked when developing for the nRF52810 is a pca10040e (emulated) project a good starting point. I'm just concerned about the word emulated and is there something about the emulated projects that should be changed for a production build.

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

awneil — Fri, 15 Feb 2019 18:46:39 GMT

pca10032 is the nRF51 (Cortex-M0) dongle - so that's no use for any nRF52 (Cortex-M4) projects!

http://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.gs.ses%2Fdita%2Fgs%2Fdeveloping%2Fchips_and_sds.html

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

Alan — Fri, 15 Feb 2019 18:14:24 GMT

Thanks, that gives me two great options. One more question, nRF52810 sample projects are all pca10040e (emulated) projects. Would a project that is targeted specifically for the pca10032 have any differences. Can I use a pca10040e project for the starting point?

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

Jørgen Holmefjord — Fri, 15 Feb 2019 09:29:13 GMT

Other serial peripherals have a EasyDMA array list feature (TWIM, SPIM), but this seems to not be an option for UARTE. However, the .PTR and .MAXCNT registers are double-buffered in the UARTE peripheral. They can be updated and prepared for the next RX/TX transmission immediately after having received the RXSTARTED/TXSTARTED event. This should allow you to setup transfers for up to 510 bytes. If you need more than this, my recommendation would be to use one of the more recent ICs that support longer EasyDMA transfers than nRF52832 for UARTE peripheral. nRF52810 have 10-bit MAXCNT register, while nRF52840 have 16-bit MAXCNT register.

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

Alan — Thu, 14 Feb 2019 21:21:27 GMT

I've been playing around with DMX. I have DMX transmit pretty much working. One way to handle the initial Break - Mark is to change the baud to 115K and transmit a 00, then change it back to 250K. I have a 513 byte DMX buffer and it needs to get sent in three pieces because of the DMA 255 byte limit. If the SoftDevice interrupts in the middle it shouldn't be a problem because the DMX spec only requires that a frame gets completed within one second. From past experience, many DMX devices will work fine if you just send 1 stop bit, but not all. So if you need to be able to transmit to any DMX device you need 2 stop bits which means the nRF52832 is not an option.

Doing a DMX receive looks like it will be more difficult. It looks like the driver supports notification of a BREAK which can be used to initiate receive of the 513 byte frame. The problem is if the SoftDevice causes a delay in the start of the receive you could start receiving data in the middle of the frame. Also, due to the DMA 256 byte limit the receive needs to be split into multiple pieces which makes for more opportunities for errors.

Is there a good way to detect if a large delay has occurred or is there a way to chain several DMA operations together to allow a longer stream of uninterrupted data?

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

awneil — Mon, 17 Dec 2018 19:49:02 GMT

If that is the case, then I'd agree with you.

It would also seem sensible that the spec writers would base their protocol on something that can be easily done with standard hardware ...

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

PM Bubblynet — Mon, 17 Dec 2018 19:41:47 GMT

hm.... that seems a bit weird idea to implement the "break"... anyways, found this: https://www.nxp.com/docs/en/application-note/AN3315.pdf

3.1 Software Implementation Because the protocol consists of an untyped byte stream produced by standard UARTs, the implementation can be easily adapted to work with any microcontroller supporting baud rates up to 250 kbps.

I would put my 5 bucks on the nRF52832 can do this... but I cant jump now to prototyping... need to finish a couple of things before holidays, will see after that how it goes...

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

awneil — Mon, 17 Dec 2018 17:04:42 GMT

But you clearly know more about it than me!

I'm just going from the opening post - but then it's not entirely clear that the poster really understood that.

Yes, the actual data frame looks to me like just a standard UART frame.

The potential problem areas seem to be in the initial "break", and the "mark after break". Possibly also the "inter-frame time".

The OP's code did that with inline delays - that is likely to get disrupted by the BLE stack ...

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

PM Bubblynet — Mon, 17 Dec 2018 16:55:32 GMT

I wouldn't call me a "DMX expert"... I am rather just a follower of our dark lord and savior all hail Google! :D

I went quickly though the UART docs https://www.nordicsemi.com/en/DocLib/Content/SDK_Doc/nRF5_SDK/v15-2-0/hardware_driver_uart cant see a reason why UART wouldn't be able to handle DMX? for example I am curious about:

[quote userid="14926" url="~/f/nordic-q-a/37567/i-am-trying-to-do-dmx512-protocol-i-hope-to-help-me-time-is-very-urgent/144723"]Only UARTE peripheral support two stop bits, and this is only supported on nRF52840 and nRF52810 ICs. Unfortunatelu, there seems to be no support for setting this in the drivers. [/quote]

it seems odd that only the baby brother and the bigger brother "supports" 2 stop bits? its just me or this is part of the protocol / formatting layer and nothing to do with UART as a driver / hardware layer?...? it seems this would be just part of the formatting library of the telegram...?

a standard 250kbit/s UART shouldn't be enough? and even then this should be enabled 2 or 3 times per second... maybe? just in case we need resources for something else? again I apologize if I am missing something basic / obvious here... I should stop being lazy and study stuff before asking :D

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

awneil — Mon, 17 Dec 2018 15:48:05 GMT

[quote userid="73023" url="~/f/nordic-q-a/37567/i-am-trying-to-do-dmx512-protocol-i-hope-to-help-me-time-is-very-urgent/162128"]this form... [/quote]

Tell me about it!!

😞

[quote userid="73023" url="~/f/nordic-q-a/37567/i-am-trying-to-do-dmx512-protocol-i-hope-to-help-me-time-is-very-urgent/162128"]Please define "strict" timing? [/quote]

Exactly. These are just "finger in the air" feelings - not detailed timing analyses

Anyhow, it sounds like you are the DMX expert here - so you're probably the best one to try it and see!

The point is that the BLE stack does have some very strict timing requirements - so whatever you do for the DMX must not mess them up - or, maybe more important, must not be messed up by the stack grabbing the CPU.

So the thing with a separate MCU is that it's the safe option.

[quote userid="73023" url="~/f/nordic-q-a/37567/i-am-trying-to-do-dmx512-protocol-i-hope-to-help-me-time-is-very-urgent/162128"]its not a big deal if we miss few packages here and there[/quote]

I think any issues are going to be with individual bit timings - rather than whole packages?

[quote userid="73023" url="~/f/nordic-q-a/37567/i-am-trying-to-do-dmx512-protocol-i-hope-to-help-me-time-is-very-urgent/162128"]similar timing requirements that any asynchronous serial protocol[/quote]

But they are usually handled in hardware - by the UART.

From the initial postings, it looked like the nRF52 UART was not (quite) going to do what DMX requires?

[quote userid="73023" url="~/f/nordic-q-a/37567/i-am-trying-to-do-dmx512-protocol-i-hope-to-help-me-time-is-very-urgent/162128"]if and when a DMX to Bluetooth translator should be on our roadmap[/quote]

If you're looking for help with that, drop me a PM ...

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

PM Bubblynet — Mon, 17 Dec 2018 15:23:42 GMT

Jesus this form... wrote a whole white paper and it didn't post it... not cool...

Anyways, short version:

Please define "strict" timing? :) DMX512 protocol is fairly simple, http://cdb.s3.amazonaws.com/ItemRelatedFiles/10191/dmx-101-handbook.pdf page 17, after that annoying break start, the info payload is divided on 512 slots with 11 bits each, 8 bit info, 1 bit start and 2 bit stop for each slot, each slot tells the intensity level 0-255, then the telegram gets repeated again and again for ever in some sort of persistent advertising... so its not a big deal if we miss few packages here and there... there will be 44 DMX per second and they will be the same most of the time... nothing fancy there... its transmitted at 250kHz... I guess the nRF52832 can handle that?? I cant see why an aditional MCU would be needed? DMX was not designed for full duplex comms, real time applications, error prevention or anything that fancy...

In summary has similar timing requirements that any asynchronous serial protocol... I cant say that it has anything specially strict...

As I mentioned before, I am just fishing around to see if and when a DMX to Bluetooth translator should be on our roadmap for Bluetooth Mesh lighting control system...

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

awneil — Wed, 12 Dec 2018 09:06:57 GMT

[quote userid="73023" url="~/f/nordic-q-a/37567/i-am-trying-to-do-dmx512-protocol-i-hope-to-help-me-time-is-very-urgent/161282"]any news?[/quote]

I though both Jørgen Holmefjord and I had already replied that the comments from 4 months ago still stand - but I can't see that in this thread any more?!

Strange.

EDIT

Oh - now they've reappeared!

The way this forum randomly hides certain posts is really unhelpful!

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

tony55723 — Wed, 12 Dec 2018 01:54:39 GMT

Maybe only the external MCU can solve, the channel has not been sent, and it is changed from uart to I/O (for the next break)

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

awneil — Tue, 11 Dec 2018 17:05:00 GMT

[quote userid="73023" url="~/f/nordic-q-a/37567/i-am-trying-to-do-dmx512-protocol-i-hope-to-help-me-time-is-very-urgent/161282"]if there is any news? [/quote]

I don't think so - I think everything that's been said remains true.

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

Jørgen Holmefjord — Tue, 11 Dec 2018 17:01:26 GMT

My comment from 4 months ago still stands. There is only one CPU core in the nRF52832. If using BLE, the softdevice will always have highest priority, the DMX protocol will have to wait, meaning that if there are strict timing requirements an external MCU might be better solution.

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

PM Bubblynet — Tue, 11 Dec 2018 16:57:24 GMT

hi, i am exploring around this DMX to BT integration and found this question and wanted to check if there is any news? is it possible to use the nRF52832 directly or needs a microcontroller to be an interface between DMX and lets say UART to the nRF52832?

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

tony55723 — Sun, 19 Aug 2018 03:20:19 GMT

The cause of the crash is the repeated call of uart_init()

But DMX512 need low voltage(Break) and high voltage(Make after break).

Another wrong place, before delay88us and delay8us

Pin number needs to be changed to 6（【nrf_gpio_pin_clear(13)】 and【 nrf_gpio_pin_set(12)】）

Screenshot error , i am sorry

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

tony55723 — Sun, 19 Aug 2018 01:43:13 GMT

Hi ,

Thank you all , for answers and suggestions.

I will try first with nRF52810 , If it doesn't work, consider using external microcontroller.

My DMX code in the main function , whether the format is correct or not , Will cause a crash

（The phone can search for BLE before adding the code, But after adding the code, it won't work.）

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

Jørgen Holmefjord — Fri, 17 Aug 2018 14:33:57 GMT

I'm not familiar with the protocol details of DMX, but if it have strict timing requirements, an external MCU might be a better solution.

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

awneil — Fri, 17 Aug 2018 14:00:11 GMT

Looks like a case where an external microcontroller would be better/easier to manage the DMX signalling ?

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

Jørgen Holmefjord — Fri, 17 Aug 2018 12:45:59 GMT

Hi,

Only UARTE peripheral support two stop bits, and this is only supported on nRF52840 and nRF52810 ICs. Unfortunatelu, there seems to be no support for setting this in the drivers.

You can set two stop bits by writing the register directly after initializing the UARTE peripheral:

NRF_UARTE0->CONFIG |= (UARTE_CONFIG_STOP_Two << UARTE_CONFIG_STOP_Pos);

The UARTE peripheral have EasyDMA support, meaning transfers can happen in the background while CPU is busy handling BLE/softdevice events. If you frequently need to handle UART events with strict timing requirements, this will not work together with the softdevice.

Best regards,
Jørgen

RE: I am trying to do DMX512 (protocol), I hope to help me, time is very urgent

tony55723 — Fri, 17 Aug 2018 09:23:24 GMT

Do I have to delete this article now?

New post article questions?

（I say sorry again）