Iis2dh

Notes on STMicro IIS22DH high frequency MEMS accelerometer.

• https://community.st.com/s/question/0D50X00009XkdfV/understanding-acceleration-data-from-iis2dh (Excerpt from this post copied to section below . . .)

A promising project on Github:

• https://github.com/STMicroelectronics/iis2dh
• https://github.com/STMicroelectronics/STMems_Standard_C_drivers/tree/master/iis2dh_STdC/examples
• https://github.com/STMicroelectronics/STMems_Standard_C_drivers/blob/master/iis2dh_STdC/examples/iis2dh_read_data_polling.c

Symbols in the polling code example from STMicroelectronic/iis2dh repo are defined in a sub-part of sdk-nrf modules/hal/ project space:

guest@ubuntu-vm:~/embedded/z3-on-var/modules/hal/st$ grep -nr IIS2DH_2g ./*
./sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.h:742:  IIS2DH_2g   = 0,
./sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.c:636:    case IIS2DH_2g:
./sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.c:637:      *val = IIS2DH_2g;
./sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.c:649:      *val = IIS2DH_2g;

guest@ubuntu-vm:~/embedded/z3-on-var/modules/hal/st$ grep -nr IIS2DH_ODR_1Hz ./*
./sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.h:707:  IIS2DH_ODR_1Hz                         = 0x01,
./sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.c:402:    case IIS2DH_ODR_1Hz:
./sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.c:403:      *val = IIS2DH_ODR_1Hz;

guest@ubuntu-vm:~/embedded/z3-on-var/modules/hal/st$ grep -nr IIS2DH_TEMP_ENABLE ./*
./sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.h:692:  IIS2DH_TEMP_ENABLE   = 3,
./sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.c:285:    case IIS2DH_TEMP_ENABLE:
./sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.c:286:      *val = IIS2DH_TEMP_ENABLE;
guest@ubuntu-vm:~/embedded/z3-on-var/modules/hal/st$ grep -nr PROPERTY_ENABLE ./*

And really the above project is pulled in to Nordic's sdk-nrf. Looks to be at a slightly older, or at least different version, but driver header and sources at https://github.com/STMicroelectronics/iis2dh are the same as in the STMicro hal code in Nordic sdk-nrf v1.6.1.

^ IIS2DH Control Registers As C Structures

An excerpt from Nordic sdk-nrf modules/hal/st/sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.h:

#define IIS2DH_CTRL_REG4             0x23U
typedef struct {
#if DRV_BYTE_ORDER == DRV_LITTLE_ENDIAN
  uint8_t sim               : 1;
  uint8_t st                : 2;
  uint8_t hr                : 1;
  uint8_t fs                : 2;
  uint8_t ble               : 1;
  uint8_t bdu               : 1;
#elif DRV_BYTE_ORDER == DRV_BIG_ENDIAN
  uint8_t bdu               : 1;
  uint8_t ble               : 1;
  uint8_t fs                : 2;
  uint8_t hr                : 1;
  uint8_t st                : 2;
  uint8_t sim               : 1;
#endif /* DRV_BYTE_ORDER */
} iis2dh_ctrl_reg4_t;

^ Possible Zephyr Driver Routines for IIS2DH

Following routines are not obvious nor mentioned anywhere in Zephyr Project documentation found so far, nor are they hinted at by any trace of analogous routines in the build artifacts of Zephyr lis2dh sample app. But may we use these following routines in app level code we want to have talking with STMicro's IIS2DH sensor? . . .

 1 guest@vm:~/projects/zephyr-based/project-stage-1$ grep -nr stmdev_ctx_t ./*
 2 Binary file ./build/zephyr/zephyr.elf matches
 3 Binary file ./build/zephyr/zephyr_prebuilt.elf matches
 4 ./build/zephyr/zephyr.lst:55935:int32_t iis2dh_read_reg(stmdev_ctx_t* ctx, uint8_t reg, uint8_t* data,
 5 ./build/zephyr/zephyr.lst:55953:int32_t iis2dh_write_reg(stmdev_ctx_t* ctx, uint8_t reg, uint8_t* data,
 6 ./build/zephyr/zephyr.lst:55973:int32_t iis2dh_operating_mode_set(stmdev_ctx_t *ctx, iis2dh_op_md_t val)
 7 ./build/zephyr/zephyr.lst:56065:int32_t iis2dh_data_rate_set(stmdev_ctx_t *ctx, iis2dh_odr_t val)
 8 ./build/zephyr/zephyr.lst:56107:int32_t iis2dh_full_scale_set(stmdev_ctx_t *ctx, iis2dh_fs_t val)
 9 ./build/zephyr/zephyr.lst:56149:int32_t iis2dh_block_data_update_set(stmdev_ctx_t *ctx, uint8_t val)
10 ./build/zephyr/zephyr.lst:56191:int32_t iis2dh_acceleration_raw_get(stmdev_ctx_t *ctx, int16_t *val)
11 ./build/zephyr/zephyr.lst:56231:int32_t iis2dh_device_id_get(stmdev_ctx_t *ctx, uint8_t *buff)
12 Binary file ./build/zephyr/CMakeFiles/zephyr.dir/home/ted/projects/zephyr-based/modules/hal/st/sensor/stmemsc/iis2dh_STdC/driver/iis2dh_reg.c.obj matches
13 Binary file ./build/zephyr/libzephyr.a matches
14 Binary file ./build/zephyr/drivers/sensor/iis2dh/CMakeFiles/drivers__sensor__iis2dh.dir/iis2dh_trigger.c.obj matches
15 Binary file ./build/zephyr/drivers/sensor/iis2dh/CMakeFiles/drivers__sensor__iis2dh.dir/iis2dh_i2c.c.obj matches
16 Binary file ./build/zephyr/drivers/sensor/iis2dh/CMakeFiles/drivers__sensor__iis2dh.dir/iis2dh.c.obj matches
17 Binary file ./build/zephyr/drivers/sensor/iis2dh/libdrivers__sensor__iis2dh.a matches
18 guest@vm:~/projects/zephyr-based/project-stage-1$

Looks like there are actually many more IIS2DH API routines available in the modules/hal source file from STMicro:

ted@localhost:~/projects/zephyr-based/z4-sandbox-kionix-work/modules/hal/st/sensor/stmemsc/iis2dh_STdC/driver$ grep -nr stmdev_ctx_t ./*.c
49:int32_t iis2dh_read_reg(stmdev_ctx_t* ctx, uint8_t reg, uint8_t* data,
67:int32_t iis2dh_write_reg(stmdev_ctx_t* ctx, uint8_t reg, uint8_t* data,
182:int32_t iis2dh_temp_status_reg_get(stmdev_ctx_t *ctx, uint8_t *buff)
196:int32_t iis2dh_temp_data_ready_get(stmdev_ctx_t *ctx, uint8_t *val)
215:int32_t iis2dh_temp_data_ovr_get(stmdev_ctx_t *ctx, uint8_t *val)
234:int32_t iis2dh_temperature_raw_get(stmdev_ctx_t *ctx, int16_t *val)
253:int32_t iis2dh_temperature_meas_set(stmdev_ctx_t *ctx, iis2dh_temp_en_t val)
275:int32_t iis2dh_temperature_meas_get(stmdev_ctx_t *ctx, iis2dh_temp_en_t *val)
304:int32_t iis2dh_operating_mode_set(stmdev_ctx_t *ctx, iis2dh_op_md_t val)
343:int32_t iis2dh_operating_mode_get(stmdev_ctx_t *ctx, iis2dh_op_md_t *val)
371:int32_t iis2dh_data_rate_set(stmdev_ctx_t *ctx, iis2dh_odr_t val)
392:int32_t iis2dh_data_rate_get(stmdev_ctx_t *ctx, iis2dh_odr_t *val)
445:int32_t iis2dh_high_pass_on_outputs_set(stmdev_ctx_t *ctx, uint8_t val)
467:int32_t iis2dh_high_pass_on_outputs_get(stmdev_ctx_t *ctx, uint8_t *val)
492:int32_t iis2dh_high_pass_bandwidth_set(stmdev_ctx_t *ctx, iis2dh_hpcf_t val)
519:int32_t iis2dh_high_pass_bandwidth_get(stmdev_ctx_t *ctx, iis2dh_hpcf_t *val)
553:int32_t iis2dh_high_pass_mode_set(stmdev_ctx_t *ctx, iis2dh_hpm_t val)
574:int32_t iis2dh_high_pass_mode_get(stmdev_ctx_t *ctx, iis2dh_hpm_t *val)
608:int32_t iis2dh_full_scale_set(stmdev_ctx_t *ctx, iis2dh_fs_t val)
629:int32_t iis2dh_full_scale_get(stmdev_ctx_t *ctx, iis2dh_fs_t *val)
663:int32_t iis2dh_block_data_update_set(stmdev_ctx_t *ctx, uint8_t val)
684:int32_t iis2dh_block_data_update_get(stmdev_ctx_t *ctx, uint8_t *val)
704:int32_t iis2dh_filter_reference_set(stmdev_ctx_t *ctx, uint8_t *buff)
720:int32_t iis2dh_filter_reference_get(stmdev_ctx_t *ctx, uint8_t *buff)
734:int32_t iis2dh_xl_data_ready_get(stmdev_ctx_t *ctx, uint8_t *val)
752:int32_t iis2dh_xl_data_ovr_get(stmdev_ctx_t *ctx, uint8_t *val)
770:int32_t iis2dh_acceleration_raw_get(stmdev_ctx_t *ctx, int16_t *val)
804:int32_t iis2dh_device_id_get(stmdev_ctx_t *ctx, uint8_t *buff)
818:int32_t iis2dh_self_test_set(stmdev_ctx_t *ctx, iis2dh_st_t val)
839:int32_t iis2dh_self_test_get(stmdev_ctx_t *ctx, iis2dh_st_t *val)
870:int32_t iis2dh_data_format_set(stmdev_ctx_t *ctx, iis2dh_ble_t val)
891:int32_t iis2dh_data_format_get(stmdev_ctx_t *ctx, iis2dh_ble_t *val)
919:int32_t iis2dh_boot_set(stmdev_ctx_t *ctx, uint8_t val)
940:int32_t iis2dh_boot_get(stmdev_ctx_t *ctx, uint8_t *val)
959:int32_t iis2dh_int_occurrencies_get(stmdev_ctx_t *ctx, uint8_t *val)
974:int32_t iis2dh_status_get(stmdev_ctx_t *ctx, iis2dh_status_reg_t *val)
1001:int32_t iis2dh_int1_gen_conf_set(stmdev_ctx_t *ctx, iis2dh_int1_cfg_t *val)
1016:int32_t iis2dh_int1_gen_conf_get(stmdev_ctx_t *ctx, iis2dh_int1_cfg_t *val)
1031:int32_t iis2dh_int1_gen_source_get(stmdev_ctx_t *ctx, iis2dh_int1_src_t *val)
1047:int32_t iis2dh_int1_gen_threshold_set(stmdev_ctx_t *ctx, uint8_t val)
1070:int32_t iis2dh_int1_gen_threshold_get(stmdev_ctx_t *ctx, uint8_t *val)
1090:int32_t iis2dh_int1_gen_duration_set(stmdev_ctx_t *ctx, uint8_t val)
1114:int32_t iis2dh_int1_gen_duration_get(stmdev_ctx_t *ctx, uint8_t *val)
1147:int32_t iis2dh_int2_gen_conf_set(stmdev_ctx_t *ctx, iis2dh_int2_cfg_t *val)
1162:int32_t iis2dh_int2_gen_conf_get(stmdev_ctx_t *ctx, iis2dh_int2_cfg_t *val)
1176:int32_t iis2dh_int2_gen_source_get(stmdev_ctx_t *ctx, iis2dh_int2_src_t *val)
1192:int32_t iis2dh_int2_gen_threshold_set(stmdev_ctx_t *ctx, uint8_t val)
1215:int32_t iis2dh_int2_gen_threshold_get(stmdev_ctx_t *ctx, uint8_t *val)
1235:int32_t iis2dh_int2_gen_duration_set(stmdev_ctx_t *ctx, uint8_t val)
1259:int32_t iis2dh_int2_gen_duration_get(stmdev_ctx_t *ctx, uint8_t *val)
1291:int32_t iis2dh_high_pass_int_conf_set(stmdev_ctx_t *ctx, iis2dh_hp_t val)
1312:int32_t iis2dh_high_pass_int_conf_get(stmdev_ctx_t *ctx, iis2dh_hp_t *val)
1358:int32_t iis2dh_pin_int1_config_set(stmdev_ctx_t *ctx, iis2dh_ctrl_reg3_t *val)
1373:int32_t iis2dh_pin_int1_config_get(stmdev_ctx_t *ctx, iis2dh_ctrl_reg3_t *val)
1389:int32_t iis2dh_int2_pin_detect_4d_set(stmdev_ctx_t *ctx, uint8_t val)
1411:int32_t iis2dh_int2_pin_detect_4d_get(stmdev_ctx_t *ctx, uint8_t *val)
1432:int32_t iis2dh_int2_pin_notification_mode_set(stmdev_ctx_t *ctx,
1456:int32_t iis2dh_int2_pin_notification_mode_get(stmdev_ctx_t *ctx,
1486:int32_t iis2dh_int1_pin_detect_4d_set(stmdev_ctx_t *ctx, uint8_t val)
1508:int32_t iis2dh_int1_pin_detect_4d_get(stmdev_ctx_t *ctx, uint8_t *val)
1528:int32_t iis2dh_int1_pin_notification_mode_set(stmdev_ctx_t *ctx,
1551:int32_t iis2dh_int1_pin_notification_mode_get(stmdev_ctx_t *ctx,
1580:int32_t iis2dh_pin_int2_config_set(stmdev_ctx_t *ctx, iis2dh_ctrl_reg6_t *val)
1595:int32_t iis2dh_pin_int2_config_get(stmdev_ctx_t *ctx, iis2dh_ctrl_reg6_t *val)
1622:int32_t iis2dh_fifo_set(stmdev_ctx_t *ctx, uint8_t val)
1643:int32_t iis2dh_fifo_get(stmdev_ctx_t *ctx, uint8_t *val)
1662:int32_t iis2dh_fifo_watermark_set(stmdev_ctx_t *ctx, uint8_t val)
1685:int32_t iis2dh_fifo_watermark_get(stmdev_ctx_t *ctx, uint8_t *val)
1705:int32_t iis2dh_fifo_trigger_event_set(stmdev_ctx_t *ctx, iis2dh_tr_t val)
1728:int32_t iis2dh_fifo_trigger_event_get(stmdev_ctx_t *ctx, iis2dh_tr_t *val)
1757:int32_t iis2dh_fifo_mode_set(stmdev_ctx_t *ctx, iis2dh_fm_t val)
1780:int32_t iis2dh_fifo_mode_get(stmdev_ctx_t *ctx, iis2dh_fm_t *val)
1815:int32_t iis2dh_fifo_status_get(stmdev_ctx_t *ctx, iis2dh_fifo_src_reg_t *val)
1829:int32_t iis2dh_fifo_data_level_get(stmdev_ctx_t *ctx, uint8_t *val)
1847:int32_t iis2dh_fifo_empty_flag_get(stmdev_ctx_t *ctx, uint8_t *val)
1865:int32_t iis2dh_fifo_ovr_flag_get(stmdev_ctx_t *ctx, uint8_t *val)
1883:int32_t iis2dh_fifo_fth_flag_get(stmdev_ctx_t *ctx, uint8_t *val)
1914:int32_t iis2dh_tap_conf_set(stmdev_ctx_t *ctx, iis2dh_click_cfg_t *val)
1929:int32_t iis2dh_tap_conf_get(stmdev_ctx_t *ctx, iis2dh_click_cfg_t *val)
1943:int32_t iis2dh_tap_source_get(stmdev_ctx_t *ctx, iis2dh_click_src_t *val)
1958:int32_t iis2dh_tap_threshold_set(stmdev_ctx_t *ctx, uint8_t val)
1980:int32_t iis2dh_tap_threshold_get(stmdev_ctx_t *ctx, uint8_t *val)
2001:int32_t iis2dh_shock_dur_set(stmdev_ctx_t *ctx, uint8_t val)
2024:int32_t iis2dh_shock_dur_get(stmdev_ctx_t *ctx, uint8_t *val)
2046:int32_t iis2dh_quiet_dur_set(stmdev_ctx_t *ctx, uint8_t val)
2071:int32_t iis2dh_quiet_dur_get(stmdev_ctx_t *ctx, uint8_t *val)
2093:int32_t iis2dh_double_tap_timeout_set(stmdev_ctx_t *ctx, uint8_t val)
2117:int32_t iis2dh_double_tap_timeout_get(stmdev_ctx_t *ctx, uint8_t *val)
2151:int32_t iis2dh_act_threshold_set(stmdev_ctx_t *ctx, uint8_t val)
2174:int32_t iis2dh_act_threshold_get(stmdev_ctx_t *ctx, uint8_t *val)
2194:int32_t iis2dh_act_timeout_set(stmdev_ctx_t *ctx, uint8_t val)
2216:int32_t iis2dh_act_timeout_get(stmdev_ctx_t *ctx, uint8_t *val)
2248:int32_t iis2dh_spi_mode_set(stmdev_ctx_t *ctx, iis2dh_sim_t val)
2269:int32_t iis2dh_spi_mode_get(stmdev_ctx_t *ctx, iis2dh_sim_t *val)

ted@localhost:~/projects/zephyr-based/z4-sandbox-kionix-work/modules/hal/st/sensor/stmemsc/iis2dh_STdC/driver$ 

^ Zephyr RTOS Tie-In To STMicro IIS2DH Driver API

File `$ENV{ZEPHYR_BASE}/drivers/sensor/iis2dh/iis2dh.c` end with:ii2

312 struct iis2dh_data iis2dh_data;
313
314 DEVICE_DT_INST_DEFINE(0, iis2dh_init, NULL,
315              &iis2dh_data, &iis2dh_cfg, POST_KERNEL,
316              CONFIG_SENSOR_INIT_PRIORITY, &iis2dh_driver_api);

...Somewhere data member `&iis2dh_data` gets assigned a value. This data member in turn is referenced when the above driver API routines are called. For example in routine `iis2dh_sample_fetch()` there is reference to an stmdev_ctx_t structure that's assigned to the device handle's "data" member:

203 static int iis2dh_sample_fetch(const struct device *dev,
204                                enum sensor_channel chan)
205 {
206         struct iis2dh_data *iis2dh = dev->data;
207         int16_t buf[3];
208
209         /* fetch raw data sample */
210         if (iis2dh_acceleration_raw_get(iis2dh->ctx, buf) < 0) {
211                 LOG_DBG("Failed to fetch raw data sample");
212                 return -EIO;
213         }
214
215         iis2dh->acc[0] = sys_le16_to_cpu(buf[0]);
216         iis2dh->acc[1] = sys_le16_to_cpu(buf[1]);
217         iis2dh->acc[2] = sys_le16_to_cpu(buf[2]);
218
219         return 0;
220 }

The structure `iis2dh_data` is defined in corresponding header file `iis2dh.h` as:

 59 /* sensor data */
 60 struct iis2dh_data {
 61         const struct device *bus;
 62         int16_t acc[3];
 63         uint32_t gain;
 64
 65         stmdev_ctx_t *ctx;
 66 #ifdef CONFIG_IIS2DH_TRIGGER
 67         const struct device *dev;
 68         const struct device *gpio;
 69         uint8_t gpio_pin;
 70         struct gpio_callback gpio_cb;
 71         sensor_trigger_handler_t drdy_handler;
 72 #if defined(CONFIG_IIS2DH_TRIGGER_OWN_THREAD)
 73         K_KERNEL_STACK_MEMBER(thread_stack, CONFIG_IIS2DH_THREAD_STACK_SIZE);
 74         struct k_thread thread;
 75         struct k_sem gpio_sem;
 76 #elif defined(CONFIG_IIS2DH_TRIGGER_GLOBAL_THREAD)
 77         struct k_work work;
 78 #endif /* CONFIG_IIS2DH_TRIGGER_GLOBAL_THREAD */
 79 #endif /* CONFIG_IIS2DH_TRIGGER */
 80 #if DT_INST_SPI_DEV_HAS_CS_GPIOS(0)
 81         struct spi_cs_control cs_ctrl;
 82 #endif
 83 };

Structure stmdev_ctx_t is defined:

110 typedef int32_t (*stmdev_write_ptr)(void *, uint8_t, uint8_t*, uint16_t);
111 typedef int32_t (*stmdev_read_ptr) (void *, uint8_t, uint8_t*, uint16_t);
112 
113 typedef struct {
114   /** Component mandatory fields **/
115   stmdev_write_ptr  write_reg;
116   stmdev_read_ptr   read_reg;
117   /** Customizable optional pointer **/
118   void *handle;
119 } stmdev_ctx_t;

^ Assignment To ctx Structure

So question, where is *ctx assigned a value? Ah, *ctx is assigned a value in the zephyr/drivers/sensor/iis2dh/iis2dh_i2c.c file. This value is a data structure which entails two C function pointers. Code excerpt here:

 19 #if DT_ANY_INST_ON_BUS_STATUS_OKAY(i2c)
 20
 21 static uint16_t iis2dh_i2c_slave_addr = DT_INST_REG_ADDR(0);
 22
 23 LOG_MODULE_DECLARE(IIS2DH, CONFIG_SENSOR_LOG_LEVEL);
 24
 25 static int iis2dh_i2c_read(struct iis2dh_data *data, uint8_t reg_addr,
 26                            uint8_t *value, uint16_t len)
 27 {
 28         return i2c_burst_read(data->bus, iis2dh_i2c_slave_addr,
 29                               reg_addr | 0x80, value, len);
 30 }
 31
 32 static int iis2dh_i2c_write(struct iis2dh_data *data, uint8_t reg_addr,
 33                             uint8_t *value, uint16_t len)
 34 {
 35         return i2c_burst_write(data->bus, iis2dh_i2c_slave_addr,
 36                                reg_addr | 0x80, value, len);
 37 }
 38
 39 stmdev_ctx_t iis2dh_i2c_ctx = {
 40         .read_reg = (stmdev_read_ptr) iis2dh_i2c_read,
 41         .write_reg = (stmdev_write_ptr) iis2dh_i2c_write,
 42 };
 43
 44 int iis2dh_i2c_init(const struct device *dev)
 45 {
 46         struct iis2dh_data *data = dev->data;
 47
 48         data->ctx = &iis2dh_i2c_ctx;
 49         data->ctx->handle = data;
 50
 51         return 0;
 52 }
 53 #endif /* DT_ANY_INST_ON_BUS_STATUS_OKAY(i2c) */

^ edit point

Routine `int i2c_burst_read()` is a Zephyr in-tree driver routine. In possibly erroneous C syntax the assignment from the Zephyr device structure handle on down is: dev->data->ctx->.read_reg = (stmdev_read_ptr) iis2dh_i2c_read ^^^  : Valid when *data is typecast as `struct iis2dh_data`. Routine `iis2dh_i2c_read` calls `i2c_burst_read()`, which in turn calls `i2c_write_read()`, which in turn calls 'i2c_transfer()', which would seem to be the final routine call in this call stack but in fact is a pointer to a project's given processor specific I2C peripheral: 346 __syscall int i2c_transfer(const struct device *dev, 347 struct i2c_msg *msgs, uint8_t num_msgs, 348 uint16_t addr); 349 350 static inline int z_impl_i2c_transfer(const struct device *dev, 351 struct i2c_msg *msgs, uint8_t num_msgs, 352 uint16_t addr) 353 { 354 const struct i2c_driver_api *api = 355 (const struct i2c_driver_api *)dev->api; 356 357 return api->transfer(dev, msgs, num_msgs, addr); 358 }

Excerpt from zephyr/include/drivers/i2c.h: 607 static inline int i2c_burst_read(const struct device *dev, 608 uint16_t dev_addr, 609 uint8_t start_addr, 610 uint8_t *buf, 611 uint32_t num_bytes) 612 { 613 return i2c_write_read(dev, dev_addr, 614 &start_addr, sizeof(start_addr), 615 buf, num_bytes); 616 } 572 static inline int i2c_write_read(const struct device *dev, uint16_t addr, 573 const void *write_buf, size_t num_write, 574 void *read_buf, size_t num_read) 575 { 576 struct i2c_msg msg[2]; 577 578 msg[0].buf = (uint8_t *)write_buf; 579 msg[0].len = num_write; 580 msg[0].flags = I2C_MSG_WRITE; 581 582 msg[1].buf = (uint8_t *)read_buf; 583 msg[1].len = num_read; 584 msg[1].flags = I2C_MSG_RESTART | I2C_MSG_READ | I2C_MSG_STOP; 585 586 return i2c_transfer(dev, msg, 2, addr); 587 } 346 __syscall int i2c_transfer(const struct device *dev, 347 struct i2c_msg *msgs, uint8_t num_msgs, 348 uint16_t addr); 349 350 static inline int z_impl_i2c_transfer(const struct device *dev, 351 struct i2c_msg *msgs, uint8_t num_msgs, 352 uint16_t addr) 353 { 354 const struct i2c_driver_api *api = 355 (const struct i2c_driver_api *)dev->api; 356 357 return api->transfer(dev, msgs, num_msgs, addr); 358 }

^ Why Does iis2dh_device_id_get Return 3 When No Device Connected?

Following routine in STMicro's driver API code base returns ASCII "3", decimal 51 even when no device connected. This is the ID value spec'd in the IIS2DH datasheet. How is this value getting returned? The routine in question is here:

 796 /**
 797   * @brief  DeviceWhoamI .[get]
 798   *
 799   * @param  ctx      read / write interface definitions
 800   * @param  buff     buffer that stores data read
 801   * @retval          interface status (MANDATORY: return 0 -> no Error)
 802   *
 803   */
 804 int32_t iis2dh_device_id_get(stmdev_ctx_t *ctx, uint8_t *buff)
 805 {
 806   int32_t ret;
 807   ret = iis2dh_read_reg(ctx, IIS2DH_WHO_AM_I, buff, 1);
 808   return ret;
 809 }

From comment block it looks like the value 3 in our situation is an error value coming from routine `iis2dh_read_reg()`. This routine is defined:

  39 /**
  40   * @brief  Read generic device register
  41   *
  42   * @param  ctx   read / write interface definitions(ptr)
  43   * @param  reg   register to read
  44   * @param  data  pointer to buffer that store the data read(ptr)
  45   * @param  len   number of consecutive register to read
  46   * @retval          interface status (MANDATORY: return 0 -> no Error)
  47   *
  48   */
  49 int32_t iis2dh_read_reg(stmdev_ctx_t* ctx, uint8_t reg, uint8_t* data,
  50                         uint16_t len)
  51 {
  52   int32_t ret;
  53   ret = ctx->read_reg(ctx->handle, reg, data, len);
  54   return ret;
  55 }

Ok this begs the question then where and how are the ctx function pointers assigned to point to functions? We were working to answer this question yesterday, and it is something of a repeat of a key question we faced when building the out-of-tree driver for Kionix sensor . . .

^ Configuration Post from ST Micro Forum

Excerpt on accelerator configurations from this developer: mhackney (Community Member) Edited by ST Community July 21, 2018 at 5:26 PM Posted on January 02, 2017 at 16:21

Ok, I overlooked the data sheet that Low Power mode is 8-bit data output. But that still does not explain why the data is not left aligned?

Also, here is my complete configuration to sanity check:

// setup CTRL_REG1

accelerometer_write(CTRL_REG1, 0b10011100); // ODR 5.376kHz in LPMode [7-4] Low power enable [3] Z enable [2]

// setup CTRL_REG2

accelerometer_write(CTRL_REG2, 0b00110001); //

// setup CTRL_REG3

accelerometer_write(CTRL_REG3, 0b01000000); // AOI (And Or Interrupt) on INT1 en [6]

// setup CTRL_REG6

accelerometer_write(CTRL_REG6, 0b00000000); //

// setup CTRL_REG4

accelerometer_write(CTRL_REG4, 0b00110000); // Full-scale selection 16G [5-4]

// setup CTRL_REG5

accelerometer_write(CTRL_REG5, 0b01001010); // FIFO enable [6] Latch INT1 [3]

// setup INT1_CFG

accelerometer_write(INT1_CFG, 0b00100000); // ZHIE enabled [5]

// setup INT1_THS

accelerometer_write(INT1_THS, Z_PROBE_SENSITIVITY); // 40

// setup INT1_DURATION

accelerometer_write(INT1_DURATION, 0);

^ LIS2DH Sample Fetch Routine

What is going on in this LIS2DH API routine by STMicro, especially at line 107?

 81 static int lis2dh_sample_fetch(const struct device *dev,
 82                                enum sensor_channel chan)
 83 {
 84         struct lis2dh_data *lis2dh = dev->data;
 85         size_t i;
 86         int status;
 87 
 88         __ASSERT_NO_MSG(chan == SENSOR_CHAN_ALL ||
 89                         chan == SENSOR_CHAN_ACCEL_XYZ);
 90 
 91         /*
 92          * since status and all accel data register addresses are consecutive,
 93          * a burst read can be used to read all the samples
 94          */
 95         status = lis2dh->hw_tf->read_data(dev, LIS2DH_REG_STATUS,
 96                                           lis2dh->sample.raw,
 97                                           sizeof(lis2dh->sample.raw));
 98         if (status < 0) {
 99                 LOG_WRN("Could not read accel axis data");
100                 return status;
101         }
102 
103         for (i = 0; i < (3 * sizeof(int16_t)); i += sizeof(int16_t)) {
104                 int16_t *sample =
105                         (int16_t *)&lis2dh->sample.raw[1 + i];
106 
107                 *sample = sys_le16_to_cpu(*sample);
108         }
109 
110         if (lis2dh->sample.status & LIS2DH_STATUS_DRDY_MASK) {
111                 return 0;
112         }
113 
114         return -ENODATA;
115 }

^ LIS2DH Data Structure

LIS2DH data structure, comparable to IIS2DH data structure but no `ctx` element:

220 struct lis2dh_data { 221 const struct device *bus; 222 const struct lis2dh_transfer_function *hw_tf; 223 224 union lis2dh_sample sample; 225 /* current scaling factor, in micro m/s^2 / lsb */ 226 uint32_t scale; 227 228 #ifdef CONFIG_LIS2DH_TRIGGER 229 const struct device *dev; 230 const struct device *gpio_int1; 231 const struct device *gpio_int2; 232 struct gpio_callback gpio_int1_cb; 233 struct gpio_callback gpio_int2_cb; 234 235 sensor_trigger_handler_t handler_drdy; 236 sensor_trigger_handler_t handler_anymotion; 237 atomic_t trig_flags; 238 enum sensor_channel chan_drdy; 239 240 #if defined(CONFIG_LIS2DH_TRIGGER_OWN_THREAD) 241 K_KERNEL_STACK_MEMBER(thread_stack, CONFIG_LIS2DH_THREAD_STACK_SIZE); 242 struct k_thread thread; 243 struct k_sem gpio_sem; 244 #elif defined(CONFIG_LIS2DH_TRIGGER_GLOBAL_THREAD) 245 struct k_work work; 246 #endif 247 248 #endif /* CONFIG_LIS2DH_TRIGGER */ 249 250 #if DT_ANY_INST_ON_BUS_STATUS_OKAY(spi) 251 struct spi_cs_control cs_ctrl; 252 #endif /* DT_ANY_INST_ON_BUS_STATUS_OKAY(spi) */ 253 };

207 struct lis2dh_transfer_function { 208 int (*read_data)(const struct device *dev, uint8_t reg_addr, 209 uint8_t *value, uint8_t len); 210 int (*write_data)(const struct device *dev, uint8_t reg_addr, 211 uint8_t *value, uint8_t len); 212 int (*read_reg)(const struct device *dev, uint8_t reg_addr, 213 uint8_t *value); 214 int (*write_reg)(const struct device *dev, uint8_t reg_addr, 215 uint8_t value); 216 int (*update_reg)(const struct device *dev, uint8_t reg_addr, 217 uint8_t mask, uint8_t value); 218 };