How to Bobble the Bits in the Registers

The Vogan poetry in the datasheet for the LSM9DS1 can be found here:
http://www.st.com/content/ccc/resource/t­echnical/document/datasheet/1e/3f/2a/d6/­25/eb/48/46/DM00103319.pdf/files/DM00103­319.pdf/jcr:content/translations/en.DM00­103319.pdf
In section six the register mapping is described. This lets us write a table to reference the registers in the code. For example the gyro and accelerometer registers are defined:

var Regs={
ACT_THS: 04, ACT_DUR: 05, INT_GEN_CFG_XL: 06, INT_GEN_THS_X_XL: 07, INT_GEN_THS_Y_XL: 08,
INT_GEN_THS_Z_XL: 09, INT_GEN_DUR_XL: 0x0A, REFERENCE_G: 0x0B, INT1_CTRL: 0x0C,
INT2_CTRL: 0x0D, //Reserved -- 0E -- -- Reserved
WHO_AM_I: 0x0F, CTRL_REG1_G: 0x10, CTRL_REG2_G: 0x11, CTRL_REG3_G: 0x12,
ORIENT_CFG_G: 0x13, INT_GEN_SRC_G: 0x14, OUT_TEMP_L: 0x15, OUT_TEMP_H: 0x16,
STATUS_REG1: 0x17, OUT_X_L_G: 0x18, OUT_X_H_G: 0x19, OUT_Y_L_G: 0x1A,
OUT_Y_H_G: 0x1B, OUT_Z_L_G: 0x1C, OUT_Z_H_G: 0x1D, 
CTRL_REG4: 0x1E, CTRL_REG5_XL: 0x1F, CTRL_REG6_XL: 0x20, CTRL_REG7_XL: 0x21,
CTRL_REG8: 0x22, CTRL_REG9: 0x23, CTRL_REG10:0x24, //Reserved -- 25 -- -- Reserved
INT_GEN_SRC_XL: 0x26, STATUS_REG2: 0x27,
OUT_X_L_XL: 0x28, OUT_X_H_XL: 0x29, OUT_Y_L_XL: 0x2A, 
OUT_Y_H_XL: 0x2B,  OUT_Z_L_XL: 0x2C, OUT_Z_H_XL: 0x2D,
FIFO_CTRL: 0x2E, FIFO_SRC: 0x2F,
INT_GEN_CFG_G: 0x30, 
INT_GEN_THS_XH_G: 0x31, INT_GEN_THS_XL_G: 0x32, INT_GEN_THS_YH_G: 0x33,
INT_GEN_THS_YL_G: 0x34, INT_GEN_THS_ZH_G: 0x35, INT_GEN_THS_ZL_G: 0x36,
INT_GEN_DUR_G: 0x37,
//Reserved r 38-7F
};

In Section7 of the datasheet the bits in the Accelerometer and gyroscope registers are described.
For example:
7.12 CTRL_REG1_G (10h) Angular rate sensor Control Register 1.
| Bit7 | Bit6| Bit5| Bit4| Bit3| Bit2| Bit1| Bit0|
| --- | --- | --- | --- | --- | --- | --- | --- |
|ODR_G2 |ODR_G1 |ODR_G0 |FS_G1 |FS_G0 |0(1)| BW_G1 |BW_G0 |

1. This bit must be set to ‘0’ for the correct operation of the device. BW_G1 BW_G0
   Bits 5, 6, and 7 control the output data rate of the gyro.
   Bits 3, and 4 select the full scale of the gyro.
   Bit 2 is always 0, and
   Bits 0 and 1 select the gyro bandwidth.
   
   

Setting up a data structure to bobble the bits

var REGval={
/*
CTRL_REG1_G (10h)
Angular rate sensor Control Register
ODR_G2, ODR_G1, ODR_G0, FS_G1, FS_G0, 0,BW_G1, BW_G0
*/
  ODR_G:{reg:Regs.CTRL_REG1_G,shift:5,mask­:7},
  FS_G:{reg:Regs.CTRL_REG1_G,shift:3,mask:­3},
  BW_G:{reg:Regs.CTRL_REG1_G,shift:0,mask:­3},
//more stuff

And setup functions to read or write the bits

/** Use the datastructure to write bits to AG register */
LSM9DS1.prototype.AGwrite=function(R,val­ue){
var A=this.xgReadByte(R.reg);
//console.log(A,value,R,R.mask,R.shift);­
var v=value&R.mask;
//  console.log("v= "+v);
 A=A&(~(R.mask<<R.shift));
 A=A|(v<<R.shift);
// console.log("A= "+A.toString(2));
 this.xgWriteByte(R.reg,A);
};//end AGwrite

/** Use the data structure to read bit settings from AG register*/
LSM9DS1.prototype.AGread=function(R){
 var A=this.xgReadByte(R.reg);
 A=A>>R.shift;
 A=A&R.mask;
// console.log("A= "+A.toString(2));
 return A;
};//end AGread

The following tests to see if the communication is working, performs a reset, writes and then reads a value to the ODR bits and then iterates thru the data structure to read and display all the bits.

/** 'run() initializes the LSM9DS1' */
LSM9DS1.prototype.run=function(){
 var i;
var xgTest = this.xgReadByte(Regs.WHO_AM_I_XG);
 console.log("XG replied "+xgTest);

console.log("do a reset");
this.AGwrite(REGval.SW_RESET,1);
console.log("SWreset= "+this.AGread(REGval.SW_RESET));
//
console.log("try writing to the ODR_G bits");
this.AGwrite(REGval.ODR_G,7);
  console.log("ODR_G= "+this.AGread(REGval.ODR_G));
console.log("iterate thru all the AG settings");
for (var x in REGval)
  console.log(x,this.AGread(REGval[x]));

  return 1;
};//end run

The output looks like this:

1v92 Copyright 2016 G.Williams
>
=undefined
XG replied 104
do a reset
SWreset= 0
try writing to the ODR_G bits
ODR_G= 7
iterate thru all the AG settings
ODR_G 7
FS_G 0
BW_G 0
G_INT_SEL 0
G_OUT_SEL 0
G_LP_mode 0
G_HP_EN 0
HPCF_G 0
SignX_G 0
SignY_G 0
SignZ_G 0
Orient_G 0
Dec_XL 0
Zen_XL 1
Yen_XL 1
Xen_XL 1
ODR_XL 0
FS_XL 0
BW_SCAL_ODR_XL 0
BW_XL 0
HR_XL 0
DCF_XL 0
FDS_XL 0
HPIS1_XL 0
BOOT 0
BDU 0
H_LACTIVE 0
PP_OD 0
SIM 0
IF_ADD_INC 1
BLE 0
SW_RESET 0
SLEEPG 0
FIFO_TEMP_EN 0
DRDY_mask_bit 0
I2C_DISABLE 0
FIFO_EN 0
STOP_ON_FTH 0
ST_G 0
ST_XL 0
FMODE 0
FTH 0
>

1 Attachment

• AGcode1.js