From b6b306103c207df61cd752d825d54c03ef89ead8 Mon Sep 17 00:00:00 2001
From: Alexander Entinger <cto@lxrobotics.com>
Date: Mon, 3 Apr 2023 12:30:55 +0200
Subject: [PATCH] Fix: Extract SPI.beginTransaction from select/deselect
 callbacks as it breaks when called in ISR context from mbed-based boards.
 (#82)

---
 .../MCP2515-CAN-Sniffer/MCP2515-CAN-Sniffer.ino     | 13 +++----------
 examples/MCP2515-Filter/MCP2515-Filter.ino          | 13 +++----------
 examples/MCP2515-Loopback/MCP2515-Loopback.ino      | 13 +++----------
 3 files changed, 9 insertions(+), 30 deletions(-)

diff --git a/examples/MCP2515-CAN-Sniffer/MCP2515-CAN-Sniffer.ino b/examples/MCP2515-CAN-Sniffer/MCP2515-CAN-Sniffer.ino
index a89b0b8..f735a2d 100644
--- a/examples/MCP2515-CAN-Sniffer/MCP2515-CAN-Sniffer.ino
+++ b/examples/MCP2515-CAN-Sniffer/MCP2515-CAN-Sniffer.ino
@@ -33,16 +33,8 @@ void onReceiveBufferFull(uint32_t const, uint32_t const, uint8_t const *, uint8_
  * GLOBAL VARIABLES
  **************************************************************************************/
 
-ArduinoMCP2515 mcp2515([]()
-                       {
-                         SPI.beginTransaction(MCP2515x_SPI_SETTING);
-                         digitalWrite(MKRCAN_MCP2515_CS_PIN, LOW);
-                       },
-                       []()
-                       {
-                         digitalWrite(MKRCAN_MCP2515_CS_PIN, HIGH);
-                         SPI.endTransaction();
-                       },
+ArduinoMCP2515 mcp2515([]() { digitalWrite(MKRCAN_MCP2515_CS_PIN, LOW); },
+                       []() { digitalWrite(MKRCAN_MCP2515_CS_PIN, HIGH); },
                        [](uint8_t const d) { return SPI.transfer(d); },
                        micros,
                        onReceiveBufferFull,
@@ -59,6 +51,7 @@ void setup()
 
   /* Setup SPI access */
   SPI.begin();
+  SPI.beginTransaction(MCP2515x_SPI_SETTING);
   pinMode(MKRCAN_MCP2515_CS_PIN, OUTPUT);
   digitalWrite(MKRCAN_MCP2515_CS_PIN, HIGH);
 
diff --git a/examples/MCP2515-Filter/MCP2515-Filter.ino b/examples/MCP2515-Filter/MCP2515-Filter.ino
index f591cc4..23daab8 100644
--- a/examples/MCP2515-Filter/MCP2515-Filter.ino
+++ b/examples/MCP2515-Filter/MCP2515-Filter.ino
@@ -33,16 +33,8 @@ void onReceiveBufferFull(uint32_t const, uint32_t const, uint8_t const *, uint8_
  * GLOBAL VARIABLES
  **************************************************************************************/
 
-ArduinoMCP2515 mcp2515([]()
-                       {
-                         SPI.beginTransaction(MCP2515x_SPI_SETTING);
-                         digitalWrite(MKRCAN_MCP2515_CS_PIN, LOW);
-                       },
-                       []()
-                       {
-                         digitalWrite(MKRCAN_MCP2515_CS_PIN, HIGH);
-                         SPI.endTransaction();
-                       },
+ArduinoMCP2515 mcp2515([]() { digitalWrite(MKRCAN_MCP2515_CS_PIN, LOW); },
+                       []() { digitalWrite(MKRCAN_MCP2515_CS_PIN, HIGH); },
                        [](uint8_t const d) { return SPI.transfer(d); },
                        micros,
                        onReceiveBufferFull,
@@ -59,6 +51,7 @@ void setup()
 
   /* Setup SPI access */
   SPI.begin();
+  SPI.beginTransaction(MCP2515x_SPI_SETTING);
   pinMode(MKRCAN_MCP2515_CS_PIN, OUTPUT);
   digitalWrite(MKRCAN_MCP2515_CS_PIN, HIGH);
 
diff --git a/examples/MCP2515-Loopback/MCP2515-Loopback.ino b/examples/MCP2515-Loopback/MCP2515-Loopback.ino
index 3f8bc03..cf4c22f 100644
--- a/examples/MCP2515-Loopback/MCP2515-Loopback.ino
+++ b/examples/MCP2515-Loopback/MCP2515-Loopback.ino
@@ -67,16 +67,8 @@ static std::array<sCanTestFrame, 7> const CAN_TEST_FRAME_ARRAY =
  * GLOBAL VARIABLES
  **************************************************************************************/
 
-ArduinoMCP2515 mcp2515([]()
-                       {
-                         SPI.beginTransaction(MCP2515x_SPI_SETTING);
-                         digitalWrite(MKRCAN_MCP2515_CS_PIN, LOW);
-                       },
-                       []()
-                       {
-                         digitalWrite(MKRCAN_MCP2515_CS_PIN, HIGH);
-                         SPI.endTransaction();
-                       },
+ArduinoMCP2515 mcp2515([]() { digitalWrite(MKRCAN_MCP2515_CS_PIN, LOW); },
+                       []() { digitalWrite(MKRCAN_MCP2515_CS_PIN, HIGH); },
                        [](uint8_t const d) { return SPI.transfer(d); },
                        micros,
                        onReceiveBufferFull,
@@ -93,6 +85,7 @@ void setup()
 
   /* Setup SPI access */
   SPI.begin();
+  SPI.beginTransaction(MCP2515x_SPI_SETTING);
   pinMode(MKRCAN_MCP2515_CS_PIN, OUTPUT);
   digitalWrite(MKRCAN_MCP2515_CS_PIN, HIGH);