Date: Wed, 13 Nov 2019 23:10:56 +0100 From: Bernd Walter <ticso@cicely7.cicely.de> To: Ian Lepore <ian@freebsd.org> Cc: ticso@cicely.de, freebsd-arm@freebsd.org Subject: Re: Choose between Raspberry Pi 4B 4GB and ROCKPro64 Message-ID: <20191113221056.GA43404@cicely7.cicely.de> In-Reply-To: <d027f6b1c798ae649061c1248a12c7d0838004c0.camel@freebsd.org> References: <20191015220433.GS96402@funkthat.com> <20191112124539.GM43404@cicely7.cicely.de> <1573571378957-0.post@n6.nabble.com> <20191112221610.GN43404@cicely7.cicely.de> <20191112225251.GB4552@funkthat.com> <20191113075343.GP43404@cicely7.cicely.de> <20191113164800.GS43404@cicely7.cicely.de> <0ad483794f3f1163a852025f4aa331efde82fb7d.camel@freebsd.org> <20191113213142.GY43404@cicely7.cicely.de> <d027f6b1c798ae649061c1248a12c7d0838004c0.camel@freebsd.org>
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On Wed, Nov 13, 2019 at 02:37:29PM -0700, Ian Lepore wrote: > On Wed, 2019-11-13 at 22:31 +0100, Bernd Walter wrote: > > On Wed, Nov 13, 2019 at 01:42:13PM -0700, Ian Lepore wrote: > > > On Wed, 2019-11-13 at 17:48 +0100, Bernd Walter wrote: > > > > I just remembered that I own an FTDI FT4232H module. > > > > This one is capable of 12Mbps with 2k Buffers and high speed USB. > > > > I have it at a different location - guess I will have to drive > > > > and > > > > pick it up. > > > > > > You'll certainly have no trouble with the ftdi 4232. I've tested > > > those > > > at 6mpbs in both directions concurrently without any data loss. > > > > > > IMO, breaking free of the 115200 barrier is long overdue, but it > > > would > > > have been nice if the step up everyone took was to 921600, because > > > virtually all usb-serial support that. With line-level rather than > > > ttl-level adapters, 1mpbs is often the effective speed limit > > > because of > > > the cheap rs232 line-level chips they use. > > > > I don't think many USB uarts are capable to divide 48MHz into 921600 > > * > > oversampling without being off too much. > > The high speed ones are a different beast, since they likely have a > > PLL and run with an internal 480MHz clock. > > > > I don't think I've ever heard of a usb-serial chip that can't do > 921600, it's a "standard" speed (115200 * 4). The newer ftdi chips > still use an external 12mhz clock/crystal, but now they have an > internal pll that kicks it up to 60mhz, then the baudrate generator > divides that down. Ah right - I just thought about 48MHz USB, but of course that already requires a PLL. -- B.Walter <bernd@bwct.de> http://www.bwct.de Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.
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