From owner-freebsd-questions@FreeBSD.ORG Sun May 5 12:00:04 2013 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 2E71E562 for ; Sun, 5 May 2013 12:00:04 +0000 (UTC) (envelope-from m@mbg.pt) Received: from mail-vc0-f169.google.com (mail-vc0-f169.google.com [209.85.220.169]) by mx1.freebsd.org (Postfix) with ESMTP id EB60CAD4 for ; Sun, 5 May 2013 12:00:03 +0000 (UTC) Received: by mail-vc0-f169.google.com with SMTP id gd11so2512828vcb.0 for ; Sun, 05 May 2013 04:59:57 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=x-received:mime-version:x-originating-ip:from:date:message-id :subject:to:content-type:x-gm-message-state; bh=1ThQDk+Wd5AyIDzcbJUCHaS+2mWtVRwttMn46W0uCOc=; b=CM6x3UXpKeNdNExtCYfcH56yIjv2EiihWNBJMOnOo/mHIc3c8lu8E6gSACYZAKh6tA ynrCN7XVPRVYUvgH9UoFrXwlFOYgQVyqRdhjAKqX8Kxo5MlDsAfZb79/6mwHCE3n2nU2 2NZSPUJ4Gw2XaamdMsvBgSDr7xtI3ev/LgLCVGGCj8hOVEFPxTouH/F8Na2ElVvgvxaS h5vJpb40FxKSAfwUaZD7LRf5TTUWwvkr8z0Ap1AKxTy0ElCQZaXX4XAR2hWetR+EQTyV MhD5RIA7WEX0o17RGug2k9BYsfSQvYED5nuXJRFdcuvSpnDB39OUSYn+11FvwsR/bMX1 Xmgw== X-Received: by 10.58.173.36 with SMTP id bh4mr5708156vec.9.1367755197250; Sun, 05 May 2013 04:59:57 -0700 (PDT) MIME-Version: 1.0 Received: by 10.221.9.70 with HTTP; Sun, 5 May 2013 04:59:17 -0700 (PDT) X-Originating-IP: [188.82.153.128] From: =?ISO-8859-1?Q?Miguel_Barbosa_Gon=E7alves?= Date: Sun, 5 May 2013 12:59:17 +0100 Message-ID: Subject: Disable FIFO on UART To: freebsd-questions@freebsd.org Content-Type: text/plain; charset=ISO-8859-1 X-Gm-Message-State: ALoCoQk2o1TVN0UOHWJUZmsd4ZCYjGzY0x2hCDPrEYJLpHyEZUlMNzxzxO6dKk2YyKYtKI+Pl7GL X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 05 May 2013 12:00:04 -0000 Hi! Back in FreeBSD 7 there was a flag to disable the FIFO on the sio device driver. From http://www.freebsd.org/cgi/man.cgi?query=sio&apropos=0&sektion=0&manpath=FreeBSD+7.4-stable&arch=default&format=html: Meaning of flags: 0x00001 shared IRQs 0x00002 disable FIFO 0x00004 no AST/4 compatible IRQ control register 0x00008 recover sooner from lost output interrupts 0x00010 device is potential system console 0x00020 device is forced to become system console 0x00040 device is reserved for low-level IO (e.g. for remote kernel debugging) 0x00080 use this port for remote kernel debugging 0x0??00 minor number of master port 0x10000 PPS timestamping on CTS instead of DCD 0x20000 device is assumed to use a 16650A-type (extended FIFO) chip Now with FreeBSD 8 which uses the UART device driver there's no option for that. I am looking to reduce the jitter I am getting on the serial port when connecting a GPS to the server. Can anyone help? Regards, Miguel