I'm currently discussing this with a Sensortek engineer. Quote: "scale0 = (1.5+1.5)*9.81/(2^6-1) = 0.4671 m/s^2 scale1 = (6+6)*9.81/(2^8-1) = 0.4616 m/s^2 scale2 = (16+16)*9.81/(2^8-1) = 1.2311 m/s^2 but you may interprete scale0 = scale1 to simplify this problem. " So I was pretty close. The 'rev' bit found in the data registers, according to the datasheet (see page 11) is 'reserved', so it should be ignored. Regarding the 6bit mode, perhaps it consumes less power than the 8bit modes? Otherwise I can't see any other advantages. I don't think the 'tilt status' register is related to raw accel readings. They've just sent me a new version of the datasheet which also describes an initialization procedure. I'll send a new version of the driver once it's ready. Regards, Tiberiu ________________________________________ From: Jonathan Cameron [jic23@xxxxxxxxxx] Sent: Wednesday, May 06, 2015 8:35 PM To: Breana, Tiberiu A; linux-iio@xxxxxxxxxxxxxxx; pmeerw@xxxxxxxxxx; Jonathan Cameron Subject: Re: [PATCH] iio: accel: Add support for Sensortek STK8312 On 06/05/15 14:12, Breana, Tiberiu A wrote: > Thanks for the reviews. > > The accelerometer has 3 measurement ranges: > -1.5g - +1.5g (6 bit, signed) > -6g - +6g (8 bit, signed) > -16g - +16g (8 bit, signed) > > scale1 = 1.5 * 9.81 / 31 ~= 0.4747 > scale2 = 6 * 9.81 / 127 ~= 0.4634 > scale3 = 16 * 9.81 / 127 ~= 1.2359 Um.. Given these are two's complement, you are going to be asymmetric so question is, are you correct that the maximum is +6G etc or is it that the minimum is -6G? If the -6G option then this all looks a bit more sensible... scale1 = 1.5*9.81/32 = 0.4598 scale2 = 6*9.81/128 = 0.4598 scale3 = whatever. I guess either you need to chase someone to clarity this or get some steady state measurements on the floor of the two scales and perform a lot of averaging to see what how they actually line up. I'm particularly suspicious of your interpretation as the sensitivities are the same for the two scales... Now conjecturing further. Why does the 1.5G version exist seeing as you don't seem to gain anything from using it? Same accuracy over a reduced range,. The answer is that it exposes the rev and alert bits allowing you to know if you read at a 'dangerous time' and need to reread. The rev bit appears to be undocumented (at least a search doesn't find the docs for me). So what we actually have is a device that really has two resolutions. The 6 bit one allows you to read just 3 registers to know if you got good data, the 8 bit reads exactly the same (+ 2 more adc pipeline stages to get the range) but requires you to also check the tilt status register (I think...) to find out if you got a good read. Next question is whether anyone will ever care about 1 more register read... If not we could just not support the 6bit mode at all. Jonathan > > Thus the resulting, non-monotonic scales. > I'll upload v2 with the rest of the suggested changes. > > Regards, > Tiberiu > ________________________________________ > From: linux-iio-owner@xxxxxxxxxxxxxxx [linux-iio-owner@xxxxxxxxxxxxxxx] on behalf of Jonathan Cameron [jic23@xxxxxxxxxxxxxxxxxxxxx] > Sent: Tuesday, May 05, 2015 4:43 PM > To: Breana, Tiberiu A; linux-iio@xxxxxxxxxxxxxxx > Cc: Jonathan Cameron > Subject: Re: [PATCH] iio: accel: Add support for Sensortek STK8312 > > On 5 May 2015 14:20:38 GMT+01:00, Tiberiu Breana <tiberiu.a.breana@xxxxxxxxx> wrote: >> Minimal implementation of an IIO driver for the Sensortek >> STK8312 3-axis accelerometer. >> Datasheet: >> http://www.syi-group.com/uploadpic/data/201361817562681623.pdf >> >> Includes: >> - ACPI support; >> - read_raw for x,y,z axes; >> - reading and setting the scale (range) parameter. >> - power management >> >> Signed-off-by: Tiberiu Breana <tiberiu.a.breana@xxxxxxxxx> > > Looks good. Will take another look when not stuck with only my phone (and a case of broken circuit boards) whilst my laptop is in the hold of the plane... >> --- >> drivers/iio/accel/Kconfig | 11 ++ >> drivers/iio/accel/Makefile | 2 + >> drivers/iio/accel/stk8312.c | 375 >> ++++++++++++++++++++++++++++++++++++++++++++ >> 3 files changed, 388 insertions(+) >> create mode 100644 drivers/iio/accel/stk8312.c >> >> diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig >> index 7c9a9a9..8bd8ccb 100644 >> --- a/drivers/iio/accel/Kconfig >> +++ b/drivers/iio/accel/Kconfig >> @@ -136,4 +136,15 @@ config MMA9553 >> >> To compile this driver as a module, choose M here: the module >> will be called mma9553. >> + >> +config STK8312 >> + tristate "Sensortek STK8312 3-Axis Accelerometer Driver" >> + depends on I2C >> + help >> + Say yes here to get support for the Sensortek STK8312 3-axis >> + accelerometer. >> + >> + Choosing M will build the driver as a module. If so, the module >> + will be called stk8312. >> + >> endmenu >> diff --git a/drivers/iio/accel/Makefile b/drivers/iio/accel/Makefile >> index 99d89e4..8b327c1 100644 >> --- a/drivers/iio/accel/Makefile >> +++ b/drivers/iio/accel/Makefile >> @@ -14,6 +14,8 @@ obj-$(CONFIG_MMA9551_CORE) += mma9551_core.o >> obj-$(CONFIG_MMA9551) += mma9551.o >> obj-$(CONFIG_MMA9553) += mma9553.o >> >> +obj-$(CONFIG_STK8312) += stk8312.o >> + >> obj-$(CONFIG_IIO_SSP_SENSORS_COMMONS) += ssp_accel_sensor.o >> >> obj-$(CONFIG_IIO_ST_ACCEL_3AXIS) += st_accel.o >> diff --git a/drivers/iio/accel/stk8312.c b/drivers/iio/accel/stk8312.c >> new file mode 100644 >> index 0000000..ff27e6b >> --- /dev/null >> +++ b/drivers/iio/accel/stk8312.c >> @@ -0,0 +1,375 @@ >> +/** >> + * Sensortek STK8312 3-Axis Accelerometer >> + * >> + * Copyright (c) 2015, Intel Corporation. >> + * >> + * This file is subject to the terms and conditions of version 2 of >> + * the GNU General Public License. See the file COPYING in the main >> + * directory of this archive for more details. >> + * >> + * IIO driver for STK8312; 7-bit I2C address: 0x3D. >> + */ >> + >> +#include <linux/acpi.h> >> +#include <linux/i2c.h> >> +#include <linux/kernel.h> >> +#include <linux/module.h> >> +#include <linux/delay.h> >> +#include <linux/iio/iio.h> >> +#include <linux/iio/sysfs.h> >> + >> +#define STK8312_REG_XOUT 0x00 >> +#define STK8312_REG_YOUT 0x01 >> +#define STK8312_REG_ZOUT 0x02 >> +#define STK8312_REG_MODE 0x07 >> +#define STK8312_REG_STH 0x13 >> +#define STK8312_REG_RESET 0x20 >> + >> +#define STK8312_MODE_ACTIVE 1 >> +#define STK8312_MODE_STANDBY 0 >> +#define STK8312_MODE_MASK 0x01 >> +#define STK8312_RNG_MASK 0xC0 >> +#define STK8312_ALERT_MASK 0x40 >> +#define STK8312_DATA6_MASK 0x3F >> +#define STK8312_RNG_SHIFT 6 >> +#define STK8312_READ_RETRIES 16 >> + >> +#define STK8312_DRIVER_NAME "stk8312" >> + >> +#define STK8312_SCALE_AVAIL "0.4747 0.4632 1.2354" >> + >> +static const int stk8312_scale_table[][2] = { >> + {0, 474700}, {0, 463200}, {1, 235400} >> +}; >> + >> +#define STK8312_ACCEL_CHANNEL(axis) { \ >> + .type = IIO_ACCEL, \ >> + .modified = 1, \ >> + .channel2 = IIO_MOD_##axis, \ >> + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \ >> + .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \ >> +} >> + >> +static const struct iio_chan_spec stk8312_channels[] = { >> + STK8312_ACCEL_CHANNEL(X), >> + STK8312_ACCEL_CHANNEL(Y), >> + STK8312_ACCEL_CHANNEL(Z), >> +}; >> + >> +struct stk8312_data { >> + struct i2c_client *client; >> + struct mutex lock; >> + int range; >> + u8 mode; >> +}; >> + >> +static IIO_CONST_ATTR(in_accel_scale_available, STK8312_SCALE_AVAIL); >> + >> +static struct attribute *stk8312_attributes[] = { >> + &iio_const_attr_in_accel_scale_available.dev_attr.attr, >> + NULL, >> +}; >> + >> +static const struct attribute_group stk8312_attribute_group = { >> + .attrs = stk8312_attributes >> +}; >> + >> +static int stk8312_set_mode(struct stk8312_data *data, u8 mode) >> +{ >> + int ret; >> + u8 masked_reg; >> + struct i2c_client *client = data->client; >> + >> + if (mode > 1) >> + return -EINVAL; >> + else if (mode == data->mode) >> + return 0; >> + >> + ret = i2c_smbus_read_byte_data(client, STK8312_REG_MODE); >> + if (ret < 0) { >> + dev_err(&client->dev, "register read failed\n"); >> + return ret; >> + } >> + masked_reg = ret & (~STK8312_MODE_MASK); >> + masked_reg |= mode; >> + >> + ret = i2c_smbus_write_byte_data(client, STK8312_REG_MODE, >> + masked_reg); >> + if (ret < 0) >> + dev_err(&client->dev, "failed to change sensor mode\n"); >> + else >> + data->mode = mode; >> + >> + return ret; >> +} >> + >> +static int stk8312_set_range(struct stk8312_data *data, u8 range) >> +{ >> + int ret; >> + int masked_reg; >> + u8 mode; >> + struct i2c_client *client = data->client; >> + >> + if (range < 0 || range > 2) >> + return -EINVAL; >> + >> + if (range == data->range) >> + return 0; >> + >> + mode = data->mode; >> + /* We need to go in standby mode to modify registers */ >> + ret = stk8312_set_mode(data, STK8312_MODE_STANDBY); >> + if (ret < 0) >> + return ret; >> + >> + ret = i2c_smbus_read_byte_data(client, STK8312_REG_STH); >> + if (ret < 0) { >> + dev_err(&client->dev, "register read failed\n"); >> + return ret; >> + } >> + >> + masked_reg = ret & (~STK8312_RNG_MASK); >> + masked_reg |= range << STK8312_RNG_SHIFT; >> + >> + ret = i2c_smbus_write_byte_data(client, STK8312_REG_STH, masked_reg); >> + if (ret < 0) >> + dev_err(&client->dev, "failed to change sensor range\n"); >> + else >> + data->range = range; >> + >> + return stk8312_set_mode(data, mode); >> +} >> + >> +static int stk8312_read_accel(struct stk8312_data *data, int axis) >> +{ >> + int ret; >> + u8 reg; >> + int retries = STK8312_READ_RETRIES; >> + struct i2c_client *client = data->client; >> + >> + switch (axis) { >> + case IIO_MOD_X: >> + reg = STK8312_REG_XOUT; >> + break; >> + case IIO_MOD_Y: >> + reg = STK8312_REG_YOUT; >> + break; >> + case IIO_MOD_Z: >> + reg = STK8312_REG_ZOUT; >> + break; >> + default: >> + return -EINVAL; >> + } >> + >> + ret = i2c_smbus_read_byte_data(client, reg); >> + if (ret < 0) { >> + dev_err(&client->dev, "register read failed\n"); >> + return ret; >> + } >> + if (data->range == 0) { >> + /* 6bit mode */ >> + while (retries--) { >> + if (ret & STK8312_ALERT_MASK) { >> + /* The register is being updated. Try again. */ >> + msleep(20); >> + ret = i2c_smbus_read_byte_data(client, reg); >> + if (ret < 0) { >> + dev_err(&data->client->dev, >> + "register read failed\n"); >> + return ret; >> + } >> + } else { >> + ret &= STK8312_DATA6_MASK; >> + return sign_extend32(ret, 5); >> + } >> + } >> + dev_err(&data->client->dev, >> + "register read failed, data not ready\n"); >> + return -EIO; >> + } >> + /* 8bit mode */ >> + return sign_extend32(ret, 7); >> +} >> + >> +static int stk8312_read_raw(struct iio_dev *indio_dev, >> + struct iio_chan_spec const *chan, >> + int *val, int *val2, long mask) >> +{ >> + struct stk8312_data *data = iio_priv(indio_dev); >> + >> + if (chan->type != IIO_ACCEL) >> + return -EINVAL; >> + >> + switch (mask) { >> + case IIO_CHAN_INFO_RAW: >> + mutex_lock(&data->lock); >> + *val = stk8312_read_accel(data, chan->channel2); >> + mutex_unlock(&data->lock); >> + return IIO_VAL_INT; >> + case IIO_CHAN_INFO_SCALE: >> + *val = stk8312_scale_table[data->range][0]; >> + *val2 = stk8312_scale_table[data->range][1]; >> + return IIO_VAL_INT_PLUS_MICRO; >> + } >> + >> + return -EINVAL; >> +} >> + >> +static int stk8312_write_raw(struct iio_dev *indio_dev, >> + struct iio_chan_spec const *chan, >> + int val, int val2, long mask) >> +{ >> + int i; >> + int index = -1; >> + int ret; >> + struct stk8312_data *data = iio_priv(indio_dev); >> + >> + switch (mask) { >> + case IIO_CHAN_INFO_SCALE: >> + for (i = 0; i < ARRAY_SIZE(stk8312_scale_table); i++) >> + if (val == stk8312_scale_table[i][0] && >> + val2 == stk8312_scale_table[i][1]) { >> + index = i; >> + break; >> + } >> + if (index < 0) >> + return -EINVAL; >> + >> + mutex_lock(&data->lock); >> + ret = stk8312_set_range(data, index); >> + mutex_unlock(&data->lock); >> + >> + return ret; >> + } >> + >> + return -EINVAL; >> +} >> + >> +static const struct iio_info stk8312_info = { >> + .driver_module = THIS_MODULE, >> + .read_raw = stk8312_read_raw, >> + .write_raw = stk8312_write_raw, >> + .attrs = &stk8312_attribute_group, >> +}; >> + >> +static int stk8312_init(struct iio_dev *indio_dev) >> +{ >> + int ret; >> + struct stk8312_data *data = iio_priv(indio_dev); >> + struct i2c_client *client = data->client; >> + >> + /* A software reset is recommended at power-on */ >> + ret = i2c_smbus_write_byte_data(data->client, STK8312_REG_RESET, >> 0x00); >> + if (ret < 0) >> + dev_err(&client->dev, "failed to reset sensor"); >> + >> + ret = stk8312_set_mode(data, STK8312_MODE_ACTIVE); >> + if (ret < 0) >> + dev_err(&client->dev, "failed to enable sensor"); >> + >> + return ret; >> +} >> + >> +static int stk8312_probe(struct i2c_client *client, >> + const struct i2c_device_id *id) >> +{ >> + int ret; >> + struct iio_dev *indio_dev; >> + struct stk8312_data *data; >> + >> + indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); >> + if (!indio_dev) { >> + dev_err(&client->dev, "iio allocation failed!\n"); >> + return -ENOMEM; >> + } >> + >> + data = iio_priv(indio_dev); >> + data->client = client; >> + i2c_set_clientdata(client, indio_dev); >> + mutex_init(&data->lock); >> + >> + indio_dev->dev.parent = &client->dev; >> + indio_dev->info = &stk8312_info; >> + indio_dev->name = STK8312_DRIVER_NAME; >> + indio_dev->modes = INDIO_DIRECT_MODE; >> + indio_dev->channels = stk8312_channels; >> + indio_dev->num_channels = ARRAY_SIZE(stk8312_channels); >> + >> + ret = stk8312_init(indio_dev); >> + if (ret < 0) { >> + dev_err(&client->dev, "sensor initialization failed\n"); >> + return ret; >> + } >> + >> + ret = iio_device_register(indio_dev); >> + if (ret < 0) { >> + dev_err(&client->dev, "device_register failed\n"); >> + stk8312_set_mode(data, STK8312_MODE_STANDBY); >> + } >> + >> + return ret; >> +} >> + >> +static int stk8312_remove(struct i2c_client *client) >> +{ >> + struct iio_dev *indio_dev = i2c_get_clientdata(client); >> + >> + iio_device_unregister(indio_dev); >> + >> + return stk8312_set_mode(iio_priv(indio_dev), STK8312_MODE_STANDBY); >> +} >> + >> +#ifdef CONFIG_PM_SLEEP >> +static int stk8312_suspend(struct device *dev) >> +{ >> + struct stk8312_data *data; >> + >> + data = iio_priv(i2c_get_clientdata(to_i2c_client(dev))); >> + >> + return stk8312_set_mode(data, STK8312_MODE_STANDBY); >> +} >> + >> +static int stk8312_resume(struct device *dev) >> +{ >> + struct stk8312_data *data; >> + >> + data = iio_priv(i2c_get_clientdata(to_i2c_client(dev))); >> + >> + return stk8312_set_mode(data, STK8312_MODE_ACTIVE); >> +} >> + >> +static SIMPLE_DEV_PM_OPS(stk8312_pm_ops, stk8312_suspend, >> stk8312_resume); >> + >> +#define STK8312_PM_OPS (&stk8312_pm_ops) >> +#else >> +#define STK8312_PM_OPS NULL >> +#endif >> + >> +static const struct i2c_device_id stk8312_i2c_id[] = { >> + {"STK8312", 0}, >> + {} >> +}; >> + >> +static const struct acpi_device_id stk8312_acpi_id[] = { >> + {"STK8312", 0}, >> + {} >> +}; >> + >> +MODULE_DEVICE_TABLE(acpi, stk8312_acpi_id); >> + >> +static struct i2c_driver stk8312_driver = { >> + .driver = { >> + .name = "stk8312", >> + .pm = STK8312_PM_OPS, >> + .acpi_match_table = ACPI_PTR(stk8312_acpi_id), >> + }, >> + .probe = stk8312_probe, >> + .remove = stk8312_remove, >> + .id_table = stk8312_i2c_id, >> +}; >> + >> +module_i2c_driver(stk8312_driver); >> + >> +MODULE_AUTHOR("Tiberiu Breana <tiberiu.a.breana@xxxxxxxxx>"); >> +MODULE_DESCRIPTION("STK8312 3-Axis Accelerometer driver"); >> +MODULE_LICENSE("GPL v2"); > > -- > Sent from my Android device with K-9 Mail. Please excuse my brevity. > -- > To unsubscribe from this list: send the line "unsubscribe linux-iio" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
