Caught wind of a new STM32 series... - Page 1
Forum section: electronics / general

author: technix
author_rank: Super Contributor
timestamp: November 20, 2018, 04:20:02 pm
content: The local ST authorized reseller called me in for a meeting, and I caught wind of something: a new line of STM32 called STM32A7series. It does seem to me as if this line of chips would have Cortex-A7 cores, together with STM32F7/H7 as ST's way to one-up i.MXRT series and maybe even encroach into the low end i.MX6ULL market.p.s. I wish they would have a low cost dual-core STM32A7 on this roadmap, which would compete with even Zynq 7010. Currently the cheapest dual core Cortex-A chip with open documents from a world-class reputable brand (this eliminates Allwinner, MediaTek, Rockchip etc which does not provide open documents themselves. Allwinner does have open documents available but that is a community effort not affiliated or even supported by Allwinner) on Taobao is XC7Z010 - AFAIK AntMiner used that chip for its sheer cheapness for a dual core name-brand ARM chip, and just let the FPGA side go to waste.

author: mark03
author_rank: Frequent Contributor
timestamp: November 20, 2018, 06:12:30 pm
content: You're saying you *think* it has an A7 core or they told you? I'm trying to wrap my head around an STM32 with an applications processor. Doesn't make sense (nor does it compete with the iMX RT series). I'm not sure this is a good idea, unless they have been working on it since before the iMX RT announcement. They were in a hurry to get the STM32H7 released and look how that turned outAnyway, the real story with the iMX RT (IMO) is the process feature shrink, and later the transition to FD-SOI. Do we have any indication ST has been working on a low-power, 28-nm process?

author: technix
author_rank: Super Contributor
timestamp: November 20, 2018, 06:33:18 pm
content: Quote from: mark03 on November 20, 2018, 06:12:30 pmThey hinted at me that the STM32A7 line would contain Cortex-A7 cores. Existing STM32 peripherals are likely retained, think a STM32H7 with the Cortex-M7 core replaced with a Cortex-A7 core and everything else kept as-is, and hopefully either a dedicated DDR SDRAM controller for BGA packages and a stronger FMC with larger maximum RAM space for TQFP packages.

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 20, 2018, 06:39:47 pm
content: Oh! Sounds nice.I'm wondering about the possible current draw of such a beast though!

author: ajb
author_rank: Super Contributor
timestamp: November 20, 2018, 07:11:37 pm
content: Interesting! This is new territory for ST, isn't it? I know the H7s are sort of crossover MCUs, but as far as I know they haven't done anything that's firmly in application processor territory, have they?

author: Jeroen3
author_rank: Super Contributor
timestamp: November 20, 2018, 07:18:09 pm
content: You sure it's A7? Not H7x5 and H7x7 that come next year?

author: mark03
author_rank: Frequent Contributor
timestamp: November 20, 2018, 08:09:09 pm
content: Quote from: technix on November 20, 2018, 06:33:18 pmNXP/Freescale took the peripheral set from an applications processor and dropped an M7 core in place of the Ax core, => iMX RT. What you are describing seems to be the opposite, taking an applications processor core and replacing the advanced peripherals with simpler ones from an MCU. Where's the value proposition in that? Wouldn't the resulting chip just compete (and probably lose) against the applications-processor offerings from Allwinner, etc. etc.? You're interested just because the name starts with STM32?

author: richardman
author_rank: Frequent Contributor
timestamp: November 20, 2018, 08:44:52 pm
content: Maybe as they want to push the clock speed, they had to abandon internal flash anyway, and once they do that, they might as well go with the A-series for even higher speeds?

author: Siwastaja
author_rank: Super Contributor
timestamp: November 20, 2018, 08:59:37 pm
content: Quote from: mark03 on November 20, 2018, 06:12:30 pmWould you like to elaborate on that?I took the risk and designed in the STM32H7 in a product that I'd been initially designing with STM32F7 - so I've been working on STM32H7 extensively since its release and I'm not seeing any real showstoppers. Just the normal ST shit I'm already used to. Of course, on the absolute scale, more of it due to a more complex device, and more complex applications utilizing all that complexity, but that's to be expected.In general, I'm not too disappointed in ST's style of releasing buggy, poorly documented microcontrollers in a hurry - everybody does that in this complex market - and thatcouldbe fixed later - but I hate the fact they always do it "hit-and-run" style, and if the documentation is broken at the day of the release, they absolutely decline to impove it later; even catastrophic documentation errors and silicon faults need to be looked for by switching between the actual documentation and a separate errata, and they have clearly decided to only report a certain % of silicon faults in the errata, so the rest you need to find and document on your own, and possibly respin the board, and when you report these issues, they do absolutely nothing. But, I'm not seeing this utter shit on the new H7 any more I have already seen on all earlier STM32 devices.STM32H7 is also the first largish STM32 device with a really usable DMA, with its "DMAMUX". In many earlier chips, their DMA mappings were absolutely braindead with almost no useful connections so that DMA was guaranteed useful only ifoneperipheral used it - anything else, you'd need to very carefully design the DMA channel mapping during the PCB schematic/layout. This pain doesn't exist with the H7 anymore, and this fact alone helps me forgive them a lot of issues.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: November 20, 2018, 10:10:49 pm
content: Quote from: technix on November 20, 2018, 04:20:02 pmThat zynq's can price compete with other plain jane ARM chips is unbelievable to me given how expensive they are from western distibutors. Single core XC7Z007s are a bit cheaper but even those are still pricey. Is the Taobao supply reclaimed "pulls" that need to be re-balled?

author: mark03
author_rank: Frequent Contributor
timestamp: November 20, 2018, 10:28:59 pm
content: Quote from: Siwastaja on November 20, 2018, 08:59:37 pmDisclaimer: I've not used the H7 yet, so perhaps I was too harsh. But I remember it being substantially delayed, w.r.t. when it was first expected out. By the time it become available, or shortly afterward, the IMX RT announcement kind of stole ST's thunder / speed crown. I also recall reading the errata and thinking "I'm glad I waited"... although this is purely subjective. Most of my projects use STM32L4 and I've been very happy with it. I also have a client project using the F7 and have no complaints; BTW IIRC the F7 also has DMAMUX.You're right that documentation is a huge issue, and it's testament to the dire state of affairs in the industry that ST's documentation is actually not bad compared to the average. It bugs me when people shrug it off as just "the usual crap," because this was not always a problem. Go back and read the 68000-series reference manual, or anything else from the 80s. This is (A) laziness, (B) sloppiness, and (C) a shocking decline in the ability of even (or especially?) native English speakers to write a coherent paragraph.Sorry for dragging this off-topic. I still do not understand the attraction of dropping an applications-processor core into what is otherwise a high-end STM32 MCU, and I strongly doubt the rumor. Is an A7 actually that much faster, clock for clock, versus an M7? I thought the main benefit was advanced OS support. And if you're going to run Linux or Android on the thing, what's the attraction of an STM32-esque Cortex A7?

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: November 20, 2018, 10:44:38 pm
content: Quote from: mark03 on November 20, 2018, 10:28:59 pmYour impression coincided with my own. I thought why do they keep on delaying general supply month by month yet are also shipping to some select lead customers. Either they are having yield problems or serious errata problems or both.As far as combining and A7 with mcu peripheral set, I see the desirability. Peripherals are peripherals, they don't care what core is diddling the bits. And there is no requirement to run linux on an A series part. Free-rtos or equivalent run just fine.

author: richardman
author_rank: Frequent Contributor
timestamp: November 20, 2018, 11:50:43 pm
content: Quote from: mark03 on November 20, 2018, 10:28:59 pmA7 runs at higher clock. Also, if you look at all the so called IoT OS from Microsoft etc., they are Linux etc. based.Of course "IoT OS" does not need to be so big, but traditional companies run slowly.

author: mark03
author_rank: Frequent Contributor
timestamp: November 21, 2018, 12:33:23 am
content: Quote from: richardman on November 20, 2018, 11:50:43 pmSomewhere in ARM's marketing material for the CM7, I believe they mentioned an expectation that it would scale to GHz clock frequencies. And NXP/Freescale have already hinted that GHz iMX RT parts are on the way. So I don't see a big  speed gap.I am still curious whether an A7 is faster than an M7 at the same clock speed, and if so, by how much. Obviously it would depend on the benchmark, but I seem to recall browsing the CoreMark results that there was not a big difference between MCUs and MPUs/APs. Any processor architects care to comment?

author: richardman
author_rank: Frequent Contributor
timestamp: November 21, 2018, 02:04:19 am
content: M7 has a 6 stage pipeline. A7 is multi-core capable and has 8 stage pipeline.A7 has an architected optional L2 cache, and also NEON VFP.So a random stab at per-clock performance would be 10-30%, and more if more cores are available. If NEON FP is usable for the program, then much faster.

author: technix
author_rank: Super Contributor
timestamp: November 21, 2018, 03:20:45 am
content: Quote from: ajb on November 20, 2018, 07:11:37 pmNot quite: they used to make a series of ARM9 chips, and this STM32A7 line seem to me like a merger of the STM32 Cortex-M lines and that old ARM9 line of products.Quote from: mark03 on November 20, 2018, 08:09:09 pmUnlike those Allwinner offerings, this chip has vendor-provided open documentation and likely a quickly mainlined kernel all of which has vendor support, even if you are a hacker or experimenting individual.Allwinner chips are cheap, but the linux-sunxi stuff is not vendor supported, and to get that support you need to sign a contract with Allwinner promising buying a certain number of their chips, use their GPL-violating software stack and violate GPL yourself since a release of code is a breach of NDA, and not be a hacker since they only want to deal with people with companies at a certain scale or larger.Quote from: richardman on November 20, 2018, 08:44:52 pmInternal Flash is not likely to go away for ST though... They might keep one in tere with enough space to hold either a bare metal OS or a u-boot.Quote from: chickenHeadKnob on November 20, 2018, 10:10:49 pmMaybe it is a supply and demand thing. XC7Z010 is price competitive with iMX6D here.

author: stroh90
author_rank: Newbie
timestamp: November 22, 2018, 03:41:28 pm
content: Quote from: Siwastaja on November 20, 2018, 08:59:37 pm2 x HS USB please. Where is it???It seems that they implemented it internally (FS USB is actually HS capable) but couldn't be bothered to mux in the pins for a second PHY

author: MT
author_rank: Super Contributor
timestamp: November 22, 2018, 05:51:49 pm
content: Quote from: stroh90 on November 22, 2018, 03:41:28 pmHere, and dual A7.https://www.st.com/en/automotive-infotainment-and-telematics/sta1295.html

author: technix
author_rank: Super Contributor
timestamp: November 22, 2018, 06:22:02 pm
content: Quote from: stroh90 on November 22, 2018, 03:41:28 pmEven if it has two USB ports, the resource would be limited.I would very much prefer ST just throw away that Synopsys USB IP and use a proper XHCI based USB controller instead. XHCI can be implemented without USB 3.0, but it allows both OTG using that standardized interface and upgrade to USB 3.0 later when they feel the need, also XHCI can be implemented as DMA-only so even the need of dual-port PMA memory are alleviated. Using DMA-only XHCI also allows implementation of a full 127-endpoint USB controller without the cost of the packet memory.