HAL_ChibiOS: fixed RCIN on revo-mini

this also adds an attempt at using 'N' (inverted) channels for
RCIN. This doesn't work yet, but would be better for the revo-mini, as
it would allow the normal RCIN pin to be used

libraries/AP_HAL_ChibiOS/SoftSigReader.cpp

@@ -68,6 +68,9 @@ bool SoftSigReader::attach_capture_timer(ICUDriver* icu_drv, icuchannel_t chan,
         icucfg.mode = ICU_INPUT_ACTIVE_LOW;
         icucfg.dier = STM32_TIM_DIER_CC2DE;
     }
+#ifdef HAL_RCIN_IS_INVERTED
+    icucfg.mode = (icucfg.mode==ICU_INPUT_ACTIVE_LOW)?ICU_INPUT_ACTIVE_HIGH:ICU_INPUT_ACTIVE_LOW;
+#endif
     icuStart(_icu_drv, &icucfg);
     //Extended Timer Setup to enable DMA transfer
     //selected offset for TIM_CCR1 and for two words

libraries/AP_HAL_ChibiOS/hwdef/revo-mini/hwdef.dat

@@ -28,10 +28,11 @@ STDOUT_BAUDRATE 57600
 I2C_ORDER I2C1
 
 # order of UARTs (and USB)
-UART_ORDER OTG1 USART1 USART6 USART3
+UART_ORDER OTG1 USART1 USART3
 
-# we need to add support for N channels for RCIN
-# PB14 TIM8_CH2 TIM8 RCIN PULLDOWN LOW DMA_CH0
+# rcinput is PC6, which is the 3rd "PWM IN" pin (the yellow wire on a
+# revolution board)
+PC6 TIM8_CH1 TIM8 RCIN FLOAT LOW DMA_CH0
 
 # analog pins
 PC3 VDD_5V_SENS ADC1
@@ -46,11 +47,11 @@ PB5 LED_BLUE OUTPUT LOW GPIO(0)
 PB6 LED_YELLOW OUTPUT LOW GPIO(1) # optional
 PB4 LED_RED OUTPUT LOW GPIO(2)
 
-# GPS port
-PC6 USART6_TX USART6
-PC7 USART6_RX USART6
+# GPS port disabled (PC6 used for RCIN)
+#PC6 USART6_TX USART6
+#PC7 USART6_RX USART6
 
-# flexi port, telem2 (can also be I2C2)
+# flexi port, setup as GPS
 PB10 USART3_TX USART3
 PB11 USART3_RX USART3
 

libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py

@@ -540,6 +540,10 @@ def write_PWM_config(f):
         a = rc_in.label.split('_')
         chan_str = a[1][2:]
         timer_str = a[0][3:]
+        if chan_str[-1] == 'N':
+            # it is an inverted channel
+            f.write('#define HAL_RCIN_IS_INVERTED\n')
+            chan_str = chan_str[:-1]
         if not is_int(chan_str) or not is_int(timer_str):
             error("Bad timer channel %s" % rc_in.label)
         if int(chan_str) not in [1, 2]:
@@ -873,7 +877,10 @@ def build_peripheral_list():
         if type.startswith('SDIO'):
             peripherals.append(type)
         if type.startswith('TIM') and p.has_extra('RCIN'):
-            peripherals.append(p.label)
+            label = p.label
+            if label[-1] == 'N':
+                label = label[:-1]
+            peripherals.append(label)
         done.add(type)
     return peripherals