altos/lpc: Filter ADC inputs

[fw/altos] / src / lpc / ao_adc_lpc.c

diff --git a/src/lpc/ao_adc_lpc.c b/src/lpc/ao_adc_lpc.c
index 25a121b53ca6eb4391991fd645323927db101859..40173aa451315e371044a5c30e5d868b0369df3f 100644 (file)
--- a/src/lpc/ao_adc_lpc.c
+++ b/src/lpc/ao_adc_lpc.c
@@ -91,47 +91,58 @@
                         (AO_ADC_6 << 6) |      \
                         (AO_ADC_7 << 7))
 
-#define AO_ADC_CLKDIV  (AO_LPC_SYSCLK / 4500000 - 1)
+#define AO_ADC_CLKDIV  (AO_LPC_SYSCLK / 4500000)
 
-static uint8_t                 ao_adc_ready;
+static uint8_t         ao_adc_ready;
+
+static uint16_t                ao_adc_prev[AO_NUM_ADC];
+
+#define sample(id)     do {                            \
+               uint16_t        p = *prev;              \
+               uint16_t        v = lpc_adc.dr[id];     \
+               p -= p >> 4;                            \
+               p += v >> 4;                            \
+               *prev++ = p;                            \
+               *out++ = p >> 1;                        \
+       } while (0)
 
 void  lpc_adc_isr(void)
 {
        uint32_t        stat = lpc_adc.stat;
        uint16_t        *out;
+       uint16_t        *prev;
 
-       lpc_adc.cr = ((AO_ADC_MASK << LPC_ADC_CR_SEL) |
-                     (AO_ADC_CLKDIV << LPC_ADC_CR_CLKDIV) |
-                     (0 << LPC_ADC_CR_BURST) |
-                     (LPC_ADC_CR_CLKS_11 << LPC_ADC_CR_CLKS));
+       /* Turn off burst mode */
+       lpc_adc.cr = 0;
        lpc_adc.stat = 0;
 
        /* Store converted values in packet */
 
        out = (uint16_t *) &ao_data_ring[ao_data_head].adc;
+       prev = ao_adc_prev;
 #if AO_ADC_0
-       *out++ = lpc_adc.dr[0] >> 1;
+       sample(0);
 #endif
 #if AO_ADC_1
-       *out++ = lpc_adc.dr[1] >> 1;
+       sample(1);
 #endif
 #if AO_ADC_2
-       *out++ = lpc_adc.dr[2] >> 1;
+       sample(2);
 #endif
 #if AO_ADC_3
-       *out++ = lpc_adc.dr[3] >> 1;
+       sample(3);
 #endif
 #if AO_ADC_4
-       *out++ = lpc_adc.dr[4] >> 1;
+       sample(4);
 #endif
 #if AO_ADC_5
-       *out++ = lpc_adc.dr[5] >> 1;
+       sample(5); 
 #endif
 #if AO_ADC_6
-       *out++ = lpc_adc.dr[6] >> 1;
+       sample(6);
 #endif
 #if AO_ADC_7
-       *out++ = lpc_adc.dr[7] >> 1;
+       sample(7);
 #endif
 
        AO_DATA_PRESENT(AO_DATA_ADC);