Date: Wed, 13 Nov 2019 14:37:29 -0700 From: Ian Lepore <ian@freebsd.org> To: ticso@cicely.de Cc: freebsd-arm@freebsd.org Subject: Re: Choose between Raspberry Pi 4B 4GB and ROCKPro64 Message-ID: <d027f6b1c798ae649061c1248a12c7d0838004c0.camel@freebsd.org> In-Reply-To: <20191113213142.GY43404@cicely7.cicely.de> References: <7b75e2ed23e334878fbb3c1d585ffc51.squirrel@10.1.1.11> <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>
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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. -- Ian
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