From 5e950e8c5ab8aac07cf68140c6e0bdb1552e9c6f Mon Sep 17 00:00:00 2001
From: Curtis Bangert <codecae@gmail.com>
Date: Fri, 2 Feb 2018 00:07:59 -0500
Subject: [PATCH] Updated soft serial implementation to better handle VTX
 half-duplex transport

---
 src/main/drivers/io.h                |  2 ++
 src/main/drivers/serial.h            |  5 +++--
 src/main/drivers/serial_softserial.c |  6 ++++--
 src/main/io/vtx_smartaudio.c         | 11 +++++++++--
 4 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/src/main/drivers/io.h b/src/main/drivers/io.h
index 55d863003..ed9e4ceae 100644
--- a/src/main/drivers/io.h
+++ b/src/main/drivers/io.h
@@ -52,6 +52,7 @@
 #define IO_CONFIG(mode, speed, pupd) ((mode) | ((speed) << 2) | ((pupd) << 5))
 
 #define IOCFG_OUT_PP         IO_CONFIG(GPIO_MODE_OUTPUT_PP, GPIO_SPEED_FREQ_LOW,  GPIO_NOPULL)
+#define IOCFG_OUT_PP_UP      IO_CONFIG(GPIO_MODE_OUTPUT_PP, GPIO_SPEED_FREQ_LOW,  GPIO_PULLUP)
 #define IOCFG_OUT_PP_25      IO_CONFIG(GPIO_MODE_OUTPUT_PP, GPIO_SPEED_FREQ_HIGH, GPIO_NOPULL)
 #define IOCFG_OUT_OD         IO_CONFIG(GPIO_MODE_OUTPUT_OD, GPIO_SPEED_FREQ_LOW,  GPIO_NOPULL)
 #define IOCFG_AF_PP          IO_CONFIG(GPIO_MODE_AF_PP,     GPIO_SPEED_FREQ_LOW,  GPIO_NOPULL)
@@ -68,6 +69,7 @@
 #define IO_CONFIG(mode, speed, otype, pupd) ((mode) | ((speed) << 2) | ((otype) << 4) | ((pupd) << 5))
 
 #define IOCFG_OUT_PP         IO_CONFIG(GPIO_Mode_OUT, 0, GPIO_OType_PP, GPIO_PuPd_NOPULL)  // TODO
+#define IOCFG_OUT_PP_UP      IO_CONFIG(GPIO_Mode_OUT, 0, GPIO_OType_PP, GPIO_PuPd_UP)
 #define IOCFG_OUT_PP_25      IO_CONFIG(GPIO_Mode_OUT, GPIO_Speed_25MHz, GPIO_OType_PP, GPIO_PuPd_NOPULL)
 #define IOCFG_OUT_OD         IO_CONFIG(GPIO_Mode_OUT, 0, GPIO_OType_OD, GPIO_PuPd_NOPULL)
 #define IOCFG_AF_PP          IO_CONFIG(GPIO_Mode_AF,  0, GPIO_OType_PP, GPIO_PuPd_NOPULL)
diff --git a/src/main/drivers/serial.h b/src/main/drivers/serial.h
index 38bfd8847..7380c4c2c 100644
--- a/src/main/drivers/serial.h
+++ b/src/main/drivers/serial.h
@@ -43,8 +43,9 @@ typedef enum {
      * To ensure the first start bit to be sent, prepend a zero byte (0x00)
      * to actual data bytes.
      */
-    SERIAL_BIDIR_OD      = 0 << 4,
-    SERIAL_BIDIR_PP      = 1 << 4
+    SERIAL_BIDIR_OD        = 0 << 4,
+    SERIAL_BIDIR_PP        = 1 << 4,
+    SERIAL_BIDIR_NOPULL    = 1 << 5, // disable pulls in BIDIR RX mode
 } portOptions_e;
 
 typedef void (*serialReceiveCallbackPtr)(uint16_t data, void *rxCallbackData);   // used by serial drivers to return frames to app
diff --git a/src/main/drivers/serial_softserial.c b/src/main/drivers/serial_softserial.c
index ecf61fd58..4978d16e0 100644
--- a/src/main/drivers/serial_softserial.c
+++ b/src/main/drivers/serial_softserial.c
@@ -132,13 +132,15 @@ static void serialInputPortActivate(softSerial_t *softSerial)
 #ifdef STM32F1
         IOConfigGPIO(softSerial->rxIO, IOCFG_IPD);
 #else
-        IOConfigGPIOAF(softSerial->rxIO, IOCFG_AF_PP_PD, softSerial->timerHardware->alternateFunction);
+        const uint8_t pinConfig = (softSerial->port.options & SERIAL_BIDIR_NOPULL) ? IOCFG_AF_PP : IOCFG_AF_PP_PD;
+        IOConfigGPIOAF(softSerial->rxIO, pinConfig, softSerial->timerHardware->alternateFunction);
 #endif
     } else {
 #ifdef STM32F1
         IOConfigGPIO(softSerial->rxIO, IOCFG_IPU);
 #else
-        IOConfigGPIOAF(softSerial->rxIO, IOCFG_AF_PP_UP, softSerial->timerHardware->alternateFunction);
+        const uint8_t pinConfig = (softSerial->port.options & SERIAL_BIDIR_NOPULL) ? IOCFG_AF_PP : IOCFG_AF_PP_UP;
+        IOConfigGPIOAF(softSerial->rxIO, pinConfig, softSerial->timerHardware->alternateFunction);
 #endif
     }
 
diff --git a/src/main/io/vtx_smartaudio.c b/src/main/io/vtx_smartaudio.c
index 3681b9fb8..343f87c34 100644
--- a/src/main/io/vtx_smartaudio.c
+++ b/src/main/io/vtx_smartaudio.c
@@ -434,7 +434,14 @@ static void saReceiveFramer(uint8_t c)
 
 static void saSendFrame(uint8_t *buf, int len)
 {
-    serialWrite(smartAudioSerialPort, 0x00); // Generate 1st start bit
+    switch (smartAudioSerialPort->identifier) {
+        case SERIAL_PORT_SOFTSERIAL1:
+        case SERIAL_PORT_SOFTSERIAL2:
+            break;
+        default:
+            serialWrite(smartAudioSerialPort, 0x00); // Generate 1st start bit
+            break;
+    }
 
     for (int i = 0 ; i < len ; i++) {
         serialWrite(smartAudioSerialPort, buf[i]);
@@ -669,7 +676,7 @@ bool vtxSmartAudioInit(void)
 
     serialPortConfig_t *portConfig = findSerialPortConfig(FUNCTION_VTX_SMARTAUDIO);
     if (portConfig) {
-        portOptions_e portOptions = SERIAL_STOPBITS_2;
+        portOptions_e portOptions = SERIAL_STOPBITS_2 | SERIAL_BIDIR_NOPULL;
 #if defined(USE_VTX_COMMON)
         portOptions = portOptions | (vtxConfig()->halfDuplex ? SERIAL_BIDIR | SERIAL_BIDIR_PP : SERIAL_UNIDIR);
 #else