From 9097013b3b5669f7f63500a1b34f362d7baeb2b2 Mon Sep 17 00:00:00 2001
From: Terry Moore <tmm@mcci.com>
Date: Mon, 23 Dec 2019 21:42:30 -0500
Subject: [PATCH] Fix #502: add os_radio(RADIO_TX_AT), version is 3.0.99.8

---
 doc/RadioDriver.md | 10 ++++++++--
 src/lmic/lmic.h    |  4 ++--
 src/lmic/radio.c   | 11 +++++++++++
 3 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/doc/RadioDriver.md b/doc/RadioDriver.md
index 60d8533c..1473e613 100644
--- a/doc/RadioDriver.md
+++ b/doc/RadioDriver.md
@@ -71,6 +71,10 @@ The radio is placed in continuous receive mode. If a frame is received, `LMIC.os
 
 This operation is not supported in FSK mode.
 
+### `os_radio(RADIO_TX_AT)`
+
+This is like `os_radio(RADIO_TX)`, but the transmission is scheduled at `LMIC.txend`.
+
 ## Common parameters
 
 ### `LMIC.rps` (IN)
@@ -109,9 +113,11 @@ The array of data to be sent.
 
 The length of the array to be sent.
 
-### `LMIC.txend` (OUT)
+### `LMIC.txend` (IN, OUT)
+
+For `RADIO_TX_AT`, an input parameter, for the scheduled TX time.
 
-The OS time at which the TX end interrupt was recognized.
+For all transmissions, updated to the OS time at which the TX end interrupt was recognized.
 
 ## Receive parameters
 
diff --git a/src/lmic/lmic.h b/src/lmic/lmic.h
index 564d9aff..f12ffcf1 100644
--- a/src/lmic/lmic.h
+++ b/src/lmic/lmic.h
@@ -105,7 +105,7 @@ extern "C"{
 #define ARDUINO_LMIC_VERSION_CALC(major, minor, patch, local)	\
 	(((major) << 24ul) | ((minor) << 16ul) | ((patch) << 8ul) | ((local) << 0ul))
 
-#define	ARDUINO_LMIC_VERSION	ARDUINO_LMIC_VERSION_CALC(3, 0, 99, 7)	/* v3.0.99.7 */
+#define	ARDUINO_LMIC_VERSION	ARDUINO_LMIC_VERSION_CALC(3, 0, 99, 8)	/* v3.0.99.8 */
 
 #define	ARDUINO_LMIC_VERSION_GET_MAJOR(v)	\
 	(((v) >> 24u) & 0xFFu)
@@ -219,7 +219,7 @@ struct bcninfo_t {
 #endif // !DISABLE_BEACONS
 
 // purpose of receive window - lmic_t.rxState
-enum { RADIO_RST=0, RADIO_TX=1, RADIO_RX=2, RADIO_RXON=3 };
+enum { RADIO_RST=0, RADIO_TX=1, RADIO_RX=2, RADIO_RXON=3, RADIO_TX_AT=4, };
 // Netid values /  lmic_t.netid
 enum { NETID_NONE=(int)~0U, NETID_MASK=(int)0xFFFFFF };
 // MAC operation modes (lmic_t.opmode).
diff --git a/src/lmic/radio.c b/src/lmic/radio.c
index b16a5b2e..de5c567d 100644
--- a/src/lmic/radio.c
+++ b/src/lmic/radio.c
@@ -781,6 +781,8 @@ static void txfsk () {
     hal_pin_rxtx(1);
 
     // now we actually start the transmission
+    if (LMIC.txend)
+        hal_waitUntil(LMIC.txend); // busy wait until exact rx time
     LMICOS_logEventUint32("+Tx FSK", LMIC.dataLen);
     opmode(OPMODE_TX);
 }
@@ -826,6 +828,8 @@ static void txlora () {
     hal_pin_rxtx(1);
 
     // now we actually start the transmission
+    if (LMIC.txend)
+        hal_waitUntil(LMIC.txend); // busy wait until exact rx time
     LMICOS_logEventUint32("+Tx LoRa", LMIC.dataLen);
     opmode(OPMODE_TX);
 
@@ -1350,9 +1354,16 @@ void os_radio (u1_t mode) {
 
       case RADIO_TX:
         // transmit frame now
+        LMIC.txend = 0;
         starttx(); // buf=LMIC.frame, len=LMIC.dataLen
         break;
 
+      case RADIO_TX_AT:
+        if (LMIC.txend == 0)
+            LMIC.txend = 1;
+        starttx();
+        break;
+
       case RADIO_RX:
         // receive frame now (exactly at rxtime)
         startrx(RXMODE_SINGLE); // buf=LMIC.frame, time=LMIC.rxtime, timeout=LMIC.rxsyms