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Accept-Language: en-US Content-Language: en-GB X-MS-Exchange-Organization-AuthAs: Anonymous X-MS-Exchange-Organization-AuthSource: TS500.efplus4.local X-MS-Has-Attach: X-Auto-Response-Suppress: All X-MS-Exchange-Organization-SenderIdResult: Pass X-MS-Exchange-Organization-PRD: mit.edu X-MS-TNEF-Correlator: received-spf: None (protection.outlook.com: jle.co.uk does not designate permitted sender hosts) dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mitprod.onmicrosoft.com; s=selector2-mitprod-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=eTtamqpvDiUWw7NUW7bAcL2pwczZSlHJPXmLJyg/XIU=; b=FwVcz1mKhChsLi3VhS1xOhSFutqR7jRPzquVzQnPVN7Ld0w82lihrX815DC/8fcvoC8Yp7svYrtH8FsLpRvIqkISZUV+Rxjr8/AG+jCoLfRWdG2y1EHsOUYo6Ox17xpeu376h6VcNIuK57rtz1z4bt+I5eVCjJWEOCK/5PzA0A4= authentication-results: spf=none (sender IP is 69.73.180.175) smtp.mailfrom=jle.co.uk; mit.edu; dkim=none (message not signed) header.d=none;mit.edu; dmarc=none action=none header.from=jle.co.uk; user-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 errors-to: piclist-bounces@mit.edu list-id: "Microcontroller discussion list - Public." list-post: x-beenthere: piclist@mit.edu x-mailman-version: 2.1.6 x-source-args: x-source-dir: x-antiabuse: Sender Address Domain - jle.co.uk x-source: x-authenticated-sender: cedar.nocdirect.com: piclist@jle.co.uk x-topics: [PIC] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Which device? For the 18F25K22, -0.08% error at 64MHz clock according to the datasheet. John On 20/10/2020 15:50, David VanHorn wrote: > 115200 might be tough since the divisor is getting small. > 7.372800 would work, 14.745600, and so on. > > > One thing a lot of people miss, which causes baud rates to be off, is > selecting the right crystal caps. > A crystal with CL of 22pF wants (2*CL-Cp) =3D 44pF - Cp where Cp is an > estimate of the parasitics (5 to 6 pf is a good first guess) > Running 22pF caps puts you a bit high, and the oscillator might not start > in all conditions. > > > > On Tue, Oct 20, 2020 at 8:44 AM Neil wrote: > >> A bit academic, but this is bugging me... I was trying to get as close >> to 115,200 baud on a PIC18F running at 64Mhz (or thereabouts). >> At 64Mhz, best I can get is 0.8% error using SPBRG=3D34. >> Calculating backwards, to get exactly 115,200, I can't find an "exact" >> crystal. >> Shouldn't I be able to find one of those "odd" values to get exactly >> 115,200 baud at around 64Mhz? >> >> Cheers, >> -Neil. >> >> -- >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .