uart: enable selecting polarity of UART input and output pins.

use flag-set or flag-unset:
    "uart0-tx-inv"
    "uart0-rx-inv"
    "uart1-tx-inv"

This comes in handy e.g. for driving led pixels without the need to add
a hardware inverter.

Author: eriksl

config.c

@@ -41,14 +41,15 @@ static const config_flag_name_t config_flag_names[] =
 	{	flag_bh_high_sens,		"bh-high-sens"		},
 	{	flag_cpu_high_speed,	"cpu-high-speed"	},
 	{	flag_wlan_power_save,	"wlan-power-save"	},
-	{	flag_unused_1,			"unused-1",			},
-	{	flag_unused_2,			"unused-2",			},
+	{	flag_uart0_tx_inv,		"uart0-tx-inv",		},
+	{	flag_uart0_rx_inv,		"uart0-rx-inv",		},
 	{	flag_log_to_buffer,		"log-to-buffer"		},
 	{	flag_auto_sequencer,	"auto-sequencer"	},
 	{	flag_pwm1_extend,		"pwm1-extend"		},
 	{	flag_tmd_high_sens,		"tmd-high-sens"		},
 	{	flag_apds3_high_sens,	"apds3-high-sens"	},
 	{	flag_apds6_high_sens,	"apds6-high-sens"	},
+	{	flag_uart1_tx_inv,		"uart1-tx-inv",		},
 	{	flag_none,				""					},
 };
 

config.h

@@ -21,14 +21,15 @@ enum
 	flag_bh_high_sens =		1 << 3,
 	flag_cpu_high_speed =	1 << 4,
 	flag_wlan_power_save =	1 << 5,
-	flag_unused_1 =			1 << 6,
-	flag_unused_2 =			1 << 7,
+	flag_uart0_tx_inv =		1 << 6,
+	flag_uart0_rx_inv =		1 << 7,
 	flag_log_to_buffer =	1 << 8,
 	flag_auto_sequencer =	1 << 9,
 	flag_pwm1_extend =		1 << 10,
 	flag_tmd_high_sens =	1 << 11,
 	flag_apds3_high_sens =	1 << 12,
 	flag_apds6_high_sens =	1 << 13,
+	flag_uart1_tx_inv =		1 << 14,
 };
 
 void			config_flags_to_string(_Bool nl, const char *, string_t *);

uart.c

@@ -307,6 +307,15 @@ irom void uart_init(void)
 	// If the fifo contains less than this numbers of bytes, raise an
 	// interrupt.
 
+	clear_set_peri_reg_mask(UART_CONF0(0),
+			(UART_RXD_INV | UART_TXD_INV),
+			((config_flags_match(flag_uart0_tx_inv)) ? UART_TXD_INV : 0) |
+			((config_flags_match(flag_uart0_rx_inv)) ? UART_RXD_INV : 0));
+
+	clear_set_peri_reg_mask(UART_CONF0(1),
+			(UART_RXD_INV | UART_TXD_INV),
+			((config_flags_match(flag_uart1_tx_inv)) ? UART_TXD_INV : 0));
+
 	write_peri_reg(UART_CONF1(0),
 			((2 & UART_RX_TOUT_THRHD) << UART_RX_TOUT_THRHD_S) |
 			UART_RX_TOUT_EN |