change spec

Makefile

@@ -1,5 +1,5 @@
 CC=gcc
-CFLAGS=-O2 -std=gnu99 -W -Werror -Wall -Wextra -I. 
+CFLAGS=-O2 -std=c99 -W -Werror -Wall -Wextra -I. 
 all:
 	$(CC) $(CFLAGS) main.c i2c.c lis3dh.c -o lis3dh -lm
 

lis3dh.c

@@ -58,6 +58,12 @@ int lis3dh_init(lis3dh_t *lis3dh) {
     lis3dh->cfg.fifo.mode = 0xFF; /* in use if neq 0xFF */
     lis3dh->cfg.fifo.trig = 0;
     lis3dh->cfg.fifo.fth = 0;
+    lis3dh->cfg.filter.mode = 0xFF; /* in use if neq 0xFF */
+    lis3dh->cfg.filter.cutoff = 0;
+    lis3dh->cfg.filter.fds = 0;
+    lis3dh->cfg.filter.hpclick = 0;
+    lis3dh->cfg.filter.ia1 = 0;
+    lis3dh->cfg.filter.ia2 = 0;
 
     err |= lis3dh_reset(lis3dh);
 
@@ -66,13 +72,14 @@ int lis3dh_init(lis3dh_t *lis3dh) {
 
 int lis3dh_configure(lis3dh_t *lis3dh) {
 
-    uint8_t ctrl_reg1, ctrl_reg4, ctrl_reg5;
+    uint8_t ctrl_reg1, ctrl_reg2, ctrl_reg4, ctrl_reg5;
     uint8_t fifo_ctrl_reg;
     uint8_t ref;
     int err = 0;
 
     /* last 0b111 enables Z, Y and X axis */
     ctrl_reg1 = 0 | (lis3dh->cfg.rate << 4) | 0b111;
+    ctrl_reg2 = 0;
     ctrl_reg4 = 0 | (lis3dh->cfg.range << 4);
     ctrl_reg5 = 0;
     fifo_ctrl_reg = 0;
@@ -85,6 +92,16 @@ int lis3dh_configure(lis3dh_t *lis3dh) {
         fifo_ctrl_reg |= ((lis3dh->cfg.fifo.trig & 1) << 5);
     }
 
+    /* set enable filter */
+    if (lis3dh->cfg.filter.mode != 0xFF) {
+        ctrl_reg2 |= ((lis3dh->cfg.filter.mode & 0b11) << 6);
+        ctrl_reg2 |= ((lis3dh->cfg.filter.cutoff & 0b11) << 4);
+        ctrl_reg2 |= ((lis3dh->cfg.filter.fds & 1) << 3);
+        ctrl_reg2 |= ((lis3dh->cfg.filter.hpclick & 1) << 2);
+        ctrl_reg2 |= ((lis3dh->cfg.filter.ia1 & 1) << 1);
+        ctrl_reg2 |= (lis3dh->cfg.filter.ia2 & 1);
+    }
+
     /* always set block update */
     ctrl_reg4 |= 0x80;
 
@@ -99,6 +116,7 @@ int lis3dh_configure(lis3dh_t *lis3dh) {
     }
 
     err |= lis3dh->dev.write(REG_CTRL_REG1, ctrl_reg1);
+    err |= lis3dh->dev.write(REG_CTRL_REG2, ctrl_reg2);
     err |= lis3dh->dev.write(REG_CTRL_REG4, ctrl_reg4);
     err |= lis3dh->dev.write(REG_CTRL_REG5, ctrl_reg5);
     err |= lis3dh->dev.write(REG_FIFO_CTRL_REG, fifo_ctrl_reg);

lis3dh.h

@@ -37,6 +37,24 @@
 #define LIS3DH_FIFO_TRIG_INT1 0b0
 #define LIS3DH_FIFO_TRIG_INT2 0b1
 
+/* filter modes */
+/* this one is reset by reading REFERENCE (0x26) */
+#define LIS3DH_FILTER_MODE_NORMAL 0b00
+#define LIS3DH_FILTER_MODE_REFERENCE 0b01
+#define LIS3DH_FILTER_MODE_NORMAL2 0b10 /* same as 00? */
+#define LIS3DH_FILTER_MODE_AUTORESET 0b11
+
+/* filter cutoff */
+/* unfortunately, there is only a table for low-power mode,
+   and the actual cutoff-frequency depends on the ODR.
+   Naming scheme after ODR@400Hz
+   AN3308 > section 4.3.1.1 */
+#define LIS3DH_FILTER_CUTOFF_8 0b00 /* highest freq */
+#define LIS3DH_FILTER_CUTOFF_4 0b01
+#define LIS3DH_FILTER_CUTOFF_2 0b10
+#define LIS3DH_FILTER_CUTOFF_1 0b11 /* lowest freq */
+
+
 struct lis3dh_device {
 	int (*init)(void);
 	int (*read)(uint8_t reg, uint8_t *dst, uint32_t size);
@@ -45,6 +63,15 @@ struct lis3dh_device {
 	int (*deinit)(void);
 };
 
+struct lis3dh_filter_config {
+    uint8_t mode;
+    uint8_t cutoff;
+    uint8_t fds; /* 1 -> use this filter */
+    uint8_t hpclick; /* 1 -> use for "CLICK" function */
+    uint8_t ia2; /* 1 -> use for AOI func on INT 2 */
+    uint8_t ia1; /* 1 -> use for AOI func on INT 1 */
+};
+
 struct lis3dh_fifo_config {
     uint8_t fth;
     uint8_t trig;
@@ -56,6 +83,7 @@ struct lis3dh_config {
     uint8_t range; /* FS */
     uint8_t mode; /* LPen and HR */
     struct lis3dh_fifo_config fifo;
+    struct lis3dh_filter_config filter;
 };
 
 struct lis3dh_acceleration {

main.c

@@ -32,6 +32,9 @@ int main() {
     lis.cfg.range = LIS3DH_FS_2G;
     lis.cfg.rate = LIS3DH_ODR_100_HZ;
     lis.cfg.fifo.mode = LIS3DH_FIFO_MODE_NORMAL;
+    lis.cfg.filter.mode = LIS3DH_FILTER_MODE_AUTORESET;
+    lis.cfg.filter.cutoff = LIS3DH_FILTER_CUTOFF_2;
+    lis.cfg.filter.fds = 1;
 
     if (lis3dh_configure(&lis)) {
         puts("configure ERR");