Path: csiph.com!eternal-september.org!feeder.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail From: rickman Newsgroups: comp.lang.forth Subject: Re: GA144 use cases Date: Mon, 7 Sep 2015 15:06:52 -0400 Organization: A noiseless patient Spider Lines: 23 Message-ID: References: <943c2b33-d9a0-4b2a-a122-5c7d54855440@googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Mon, 7 Sep 2015 19:05:06 +0000 (UTC) Injection-Info: mx02.eternal-september.org; posting-host="03f127548f1143b691123e451e3cd25e"; logging-data="26169"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+GOG+1w3d0zAgff8C4lMmJ" User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 In-Reply-To: <943c2b33-d9a0-4b2a-a122-5c7d54855440@googlegroups.com> Cancel-Lock: sha1:NvD/d7p2w8nhtGyHPg5nse/JlRc= Xref: csiph.com comp.lang.forth:41825 On 9/7/2015 6:31 AM, Raimond Dragomir wrote: >> However a couple of nodes can start and drive a crystal oscillator. It can even stop the crystal from oscillating when not needed. This makes it uniquely suitable for application where low power is a must. E.g. imagine a data acquisition station where the data is transmitted only once a day. The communication crystal needs to run only for a few minutes during a day. >> >> I don't know any other device that can stop and restart a crystal quartz. > > Many cortex-m devices claim a sleeping sub-microampere power budget these days, including an rtc for precise waking times. I don't know if they stop the crystals or not and I don't care. Give me power figures so I can compare the things. Yes, crystals are stopped and started on any processor that is shooting for really low power levels while sleeping. They either use a second crystal, 32.768 kHz or use an internal RC slow clock to wake up by. The high speed crystal clock takes some milliseconds to restart and a low speed crystal clock takes a significant part of a second to restart and stabilize. I doubt anything done with the GA144 will significantly improve on this. In fact, they never got a general purpose high speed crystal clock to work. I think Chuck punted and used a resonator. The initial accuracy of the crystal stimulus is too critical for the GA144 tolerances. Did anyone else explore the world of crystal oscillators with the GA144? -- Rick