From 7914f7bd8b3be9dfb118d2bc0d24e3ae8dff78a1 Mon Sep 17 00:00:00 2001
From: StanJ <53401742+Tech-TX@users.noreply.github.com>
Date: Mon, 9 Dec 2019 17:51:17 -0600
Subject: [PATCH 1/2] put inline helpers in IRAM for slave ISRs [issue 6875]

---
 cores/esp8266/core_esp8266_si2c.cpp | 41 +++++++++++++++--------------
 1 file changed, 21 insertions(+), 20 deletions(-)

diff --git a/cores/esp8266/core_esp8266_si2c.cpp b/cores/esp8266/core_esp8266_si2c.cpp
index 58442e4147..a8b732f791 100644
--- a/cores/esp8266/core_esp8266_si2c.cpp
+++ b/cores/esp8266/core_esp8266_si2c.cpp
@@ -95,31 +95,32 @@ class Twi
     unsigned char read_byte(bool nack);
     void ICACHE_RAM_ATTR onTwipEvent(uint8_t status);
 
-    // Inline helpers
-    inline void SDA_LOW()
+    // !Inline helpers (linker doesn't bring them inline)
+    ICACHE_RAM_ATTR void SDA_LOW()
     {
         GPES = (1 << twi_sda);
     }
-    inline void SDA_HIGH()
+    ICACHE_RAM_ATTR void SDA_HIGH()
     {
         GPEC = (1 << twi_sda);
     }
-    inline bool SDA_READ()
+    ICACHE_RAM_ATTR bool SDA_READ()
     {
         return (GPI & (1 << twi_sda)) != 0;
     }
-    inline void SCL_LOW()
+    ICACHE_RAM_ATTR void SCL_LOW()
     {
         GPES = (1 << twi_scl);
     }
-    inline void SCL_HIGH()
+    ICACHE_RAM_ATTR void SCL_HIGH()
     {
         GPEC = (1 << twi_scl);
     }
-    inline bool SCL_READ()
+    ICACHE_RAM_ATTR bool SCL_READ()
     {
         return (GPI & (1 << twi_scl)) != 0;
     }
+	
     // Handle the case where a slave needs to stretch the clock with a time-limited busy wait
     inline void WAIT_CLOCK_STRETCH()
     {
@@ -439,6 +440,14 @@ unsigned char Twi::readFrom(unsigned char address, unsigned char* buf, unsigned
     return 0;
 }
 
+void Twi::twi_scl_valley(void)
+{
+    SCL_LOW();
+    busywait(twi_dcount);
+    SCL_HIGH();
+    WAIT_CLOCK_STRETCH();
+}
+
 uint8_t Twi::status()
 {
     WAIT_CLOCK_STRETCH();  // wait for a slow slave to finish
@@ -650,14 +659,6 @@ void ICACHE_RAM_ATTR Twi::onTwipEvent(uint8_t status)
     }
 }
 
-void Twi::twi_scl_valley(void)
-{
-    SCL_LOW();
-    busywait(twi_dcount);
-    SCL_HIGH();
-    WAIT_CLOCK_STRETCH();
-}
-
 void ICACHE_RAM_ATTR Twi::onTimer(void *unused)
 {
     (void)unused;
@@ -714,8 +715,8 @@ void ICACHE_RAM_ATTR Twi::onSclChange(void)
     unsigned int scl;
 
     // Store bool return in int to reduce final code size.
-    sda = twi.SDA_READ();
-    scl = twi.SCL_READ();
+    sda = (GPI & (1 << twi.twi_sda)) != 0; // SDA_READ() fast, no time for a call
+    scl = (GPI & (1 << twi.twi_scl)) != 0; // SCL_READ()
 
     twi.twip_status = 0xF8;		// reset TWI status
 
@@ -911,8 +912,8 @@ void ICACHE_RAM_ATTR Twi::onSdaChange(void)
     unsigned int scl;
 
     // Store bool return in int to reduce final code size.
-    sda = twi.SDA_READ();
-    scl = twi.SCL_READ();
+    sda = (GPI & (1 << twi.twi_sda)) != 0; // SDA_READ()
+    scl = (GPI & (1 << twi.twi_scl)) != 0; // SCL_READ()
 
     int twip_state_mask = S2M(twi.twip_state);
     if (scl)   /* !DATA */
@@ -1073,4 +1074,4 @@ extern "C" {
         twi.enableSlave();
     }
 
-};
+};
\ No newline at end of file

From 6dac0a820cd1da20f74182d47454bf111a373a89 Mon Sep 17 00:00:00 2001
From: StanJ <53401742+Tech-TX@users.noreply.github.com>
Date: Mon, 9 Dec 2019 18:18:40 -0600
Subject: [PATCH 2/2] put inline helpers in IRAM for slave ISRs [issue 6875]

---
 cores/esp8266/core_esp8266_si2c.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cores/esp8266/core_esp8266_si2c.cpp b/cores/esp8266/core_esp8266_si2c.cpp
index a8b732f791..fd7e8cbd68 100644
--- a/cores/esp8266/core_esp8266_si2c.cpp
+++ b/cores/esp8266/core_esp8266_si2c.cpp
@@ -1074,4 +1074,4 @@ extern "C" {
         twi.enableSlave();
     }
 
-};
\ No newline at end of file
+};