Date: Wed, 8 May 2019 14:06:01 -0500 From: Karl Denninger <karl@denninger.net> To: freebsd-arm@freebsd.org Subject: Re: FreeBsd I2C utility gives same value as MSB and LSB from DS75 sensor 16bit register. Message-ID: <7e6086f1-719a-4b24-e082-feb84d55342f@denninger.net> In-Reply-To: <CAHp9zCky5dVLfUUJqhE9jNM3Fm%2BCL-aW-Zc9gfWFRz55k4KB8w@mail.gmail.com> References: <CAHp9zCky5dVLfUUJqhE9jNM3Fm%2BCL-aW-Zc9gfWFRz55k4KB8w@mail.gmail.com>
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This is a cryptographically signed message in MIME format. --------------ms080602030209020806000700 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 5/3/2019 06:43, Prasad M wrote: > Hi Folks, > > I am trying to access a DS75 I2C temperature sensor. It kind of works w= ith > the default i2c utility. But it returns twice the high byte instead of = the > high and low byte for the temperature. Probably because it does 1 byte > reads on the I2C bus, sending a stop condition after every byte. > > The device expects continuous reads and no stop/start in between the 2 > bytes. Trying all options i2c, most notably the -m mode switch, yields = the > same results all the time. Looking at the code in i2c.c > > Could any one help to solve this problem with working I2CRDWR utility. I don't know if you can do it with that utility, but coding up a simple (~10-15 lines of "C") that reads two bytes is trivially easy. You simply stuff a message buffer requesting 2 bytes in response and call ioctl; you get back two bytes. --=20 Karl Denninger karl@denninger.net <mailto:karl@denninger.net> /The Market Ticker/ /[S/MIME encrypted email preferred]/ --------------ms080602030209020806000700 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCC DdgwggagMIIEiKADAgECAhMA5EiKghDOXrvfxYxjITXYDdhIMA0GCSqGSIb3DQEBCwUAMIGL MQswCQYDVQQGEwJVUzEQMA4GA1UECAwHRmxvcmlkYTESMBAGA1UEBwwJTmljZXZpbGxlMRkw FwYDVQQKDBBDdWRhIFN5c3RlbXMgTExDMRgwFgYDVQQLDA9DdWRhIFN5c3RlbXMgQ0ExITAf BgNVBAMMGEN1ZGEgU3lzdGVtcyBMTEMgMjAxNyBDQTAeFw0xNzA4MTcxNjQyMTdaFw0yNzA4 MTUxNjQyMTdaMHsxCzAJBgNVBAYTAlVTMRAwDgYDVQQIDAdGbG9yaWRhMRkwFwYDVQQKDBBD dWRhIFN5c3RlbXMgTExDMRgwFgYDVQQLDA9DdWRhIFN5c3RlbXMgQ0ExJTAjBgNVBAMMHEN1 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