From dbc8d791c6e0231ff421668dca64efc08733069d Mon Sep 17 00:00:00 2001
From: Johny Mattsson <johny.mattsson+github@gmail.com>
Date: Thu, 2 Mar 2017 22:29:40 +1100
Subject: [PATCH] Added node.chipid() based on esptool's formula.

---
 components/modules/node.c | 25 +++++++++++++++++++++++--
 docs/en/modules/node.md   |  5 ++++-
 2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/components/modules/node.c b/components/modules/node.c
index e9d21a84..c01e3088 100644
--- a/components/modules/node.c
+++ b/components/modules/node.c
@@ -7,14 +7,33 @@
 #include "vfs.h"
 #include "esp_system.h"
 #include "esp_log.h"
+#include "soc/efuse_reg.h"
 #include "ldebug.h"
 
-// Lua: heap()
+// Lua: node.chipid()
+static int node_chipid( lua_State *L )
+{
+  // This matches the way esptool.py generates a chipid for the ESP32 as of
+  // esptool commit e9e9179f6fc3f2ecfc568987d3224b5e53a05f06
+  // Oddly, this drops the lowest byte what's effectively the MAC address, so
+  // it would seem plausible to encounter up to 256 chips with the same chipid
+  uint64_t word16 = REG_READ(EFUSE_BLK0_RDATA1_REG);
+  uint64_t word17 = REG_READ(EFUSE_BLK0_RDATA2_REG);
+  const uint64_t MAX_UINT24 = 0xffffff;
+  uint64_t cid = ((word17 & MAX_UINT24) << 24) | ((word16 >> 8) & MAX_UINT24);
+  char chipid[17] = { 0 };
+  sprintf(chipid, "0x%llx", cid);
+  lua_pushstring(L, chipid);
+  return 1;
+}
+
+
+// Lua: node.heap()
 static int node_heap( lua_State* L )
 {
   uint32_t sz = esp_get_free_heap_size();
   lua_pushinteger(L, sz);
-return 1;
+  return 1;
 }
 
 static int node_restart (lua_State *L)
@@ -147,6 +166,7 @@ static int writer(lua_State* L, const void* p, size_t size, void* u)
   return 0;
 }
 
+
 #define toproto(L,i) (clvalue(L->top+(i))->l.p)
 // Lua: compile(filename) -- compile lua file into lua bytecode, and save to .lc
 static int node_compile( lua_State* L )
@@ -280,6 +300,7 @@ static const LUA_REG_TYPE node_task_map[] = {
 
 static const LUA_REG_TYPE node_map[] =
 {
+  { LSTRKEY( "chipid" ),	LFUNCVAL( node_chipid )	},
   { LSTRKEY( "compile" ),	LFUNCVAL( node_compile )	},
   { LSTRKEY( "dsleep" ),    LFUNCVAL( node_dsleep ) 	},
   { LSTRKEY( "egc" ),		LROVAL( node_egc_map )  	},
diff --git a/docs/en/modules/node.md b/docs/en/modules/node.md
index d2e8e725..8b0dc0a6 100644
--- a/docs/en/modules/node.md
+++ b/docs/en/modules/node.md
@@ -56,7 +56,10 @@ Returns the ESP chip ID.
 none
 
 #### Returns
-chip ID (number)
+chip ID (string)
+
+Note that due to the chip id being a much larger value on the ESP32, it is
+reported as a string now. E.g. `"0x1818fe346a88"`.
 
 ## node.compile()