@@ -98,6 +98,13 @@
#define VF610_ADC_CALF 0x2
#define VF610_ADC_TIMEOUT msecs_to_jiffies(100)
+/* V at 25°C of 696 mV */
+#define VF610_VTEMP25_3V0 950
+/* V at 25°C of 699 mV */
+#define VF610_VTEMP25_3V3 867
+/* Typical sensor slope coefficient at all temperatures */
+#define VF610_TEMP_SLOPE_COEFF 1840
+
enum clk_sel {
VF610_ADCIOC_BUSCLK_SET,
VF610_ADCIOC_ALTCLK_SET,
@@ -513,11 +520,13 @@ static int vf610_read_raw(struct iio_dev *indio_dev,
break;
case IIO_TEMP:
/*
- * Calculate in degree Celsius times 1000
- * Using sensor slope of 1.84 mV/°C and
- * V at 25°C of 696 mV
- */
- *val = 25000 - ((int)info->value - 864) * 1000000 / 1840;
+ * Calculate in degree Celsius times 1000
+ * Using the typical sensor slope of 1.84 mV/°C
+ * and VREFH_ADC at 3.3V, V at 25°C of 699 mV
+ */
+ *val = 25000 - ((int)info->value - VF610_VTEMP25_3V3) *
+ 1000000 / VF610_TEMP_SLOPE_COEFF;
+
break;
default:
mutex_unlock(&indio_dev->mlock);
This is a note to let you know that I have just added a patch titled vf610_adc: Fix internal temperature calculation to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue This patch is scheduled to be released in version 3.19.8-ckt12. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.19.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From b286482987ef4d80fb2df4846c905b5be0cb6660 Mon Sep 17 00:00:00 2001 From: Bhuvanchandra DV <bhuvanchandra.dv@toradex.com> Date: Mon, 19 Oct 2015 21:24:36 +0530 Subject: vf610_adc: Fix internal temperature calculation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit 6219f432ec037317a77c40910da12a626c34af1c upstream. Calculate ADCR_VTEMP25 using VTEMP25 at VREFH_ADC 3V3. Existing calculations consider the typical values provided in datasheet. Those typical values are valid for VREFH_ADC at 3.0V. VTEMP25 is different for different VREFH_ADC voltages. With VREFH_ADC at 3.3V, voltage at 25°C is 0.699V. Hence update the VTEMP25 to 0.699V which gives ADCR@Temp25 as 867. Formula for finding ADCR@Temp25: ADCR@Temp25 = (ADCR@Vdd * V@TEMP25 * 10) / VDDconv ADCR@Vdd for 12-Bit ADC = 4095 VDDconv = VREFH_ADC * 10 VREFH_ADC@3.3V ADCR@Temp25 = (4095 * .699 * 10) / 33 ADCR@Temp25 ~= 867 | VREFH_ADC | V@TEMP25 | VDDconv | ADCR@Temp25 | | 3.0V | 0.696mV | 30 | 950 | | 3.3V | 0.699mV | 33 | 867 | Signed-off-by: Bhuvanchandra DV <bhuvanchandra.dv@toradex.com> Acked-by: Fugang Duan <B38611@freescale.com> Signed-off-by: Jonathan Cameron <jic23@kernel.org> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- drivers/iio/adc/vf610_adc.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) -- 1.9.1