Update to v086r07 release.

byuu says:

USART improvements. The clock pulse from reading data() drives both
reading and writing.
Also added a usart_init() to bind the initializer functions, so all you
need now is:
extern "C" usartproc void usart_main() { ... }
And inside, you use usart_read(), usart_write(), etc.
So we can add all the new functions we want (eg I'd like to have
usart_readable() to check if data is available) without changing the
entry point signature.

blargg enhanced his Teensy driver to ignore frame error reads, as well.

bsnes/base/base.hpp

@@ -1,7 +1,7 @@
 #ifndef BASE_HPP
 #define BASE_HPP
 
-const char Version[] = "086.06";
+const char Version[] = "086.07";
 
 #include <nall/platform.hpp>
 #include <nall/algorithm.hpp>

bsnes/snes/controller/usart/usart.cpp

@@ -17,7 +17,8 @@
 // GND     GND
 
 void USART::enter() {
-  main({ &USART::usleep, this }, { &USART::read, this }, { &USART::write, this });
+  init({ &USART::usleep, this }, { &USART::read, this }, { &USART::write, this });
+  main();
   while(true) step(1000000);  //fallback; main should never return
 }
 
@@ -38,8 +39,20 @@ void USART::write(uint8 data) {
   rxbuffer.append(data ^ 0xff);
 }
 
-//USART -> SNES
+//clock
 uint2 USART::data() {
+  //SNES -> USART
+  if(txlength == 0 && latched == 0) {
+    txlength++;
+  } else if(txlength <= 8) {
+    txdata = (latched << 7) | (txdata >> 1);
+    txlength++;
+  } else {
+    if(latched == 1) txbuffer.append(txdata);
+    txlength = 0;
+  }
+
+  //USART -> SNES
   if(rxlength == 0 && rxbuffer.size()) {
     data1 = 1;
     rxdata = rxbuffer[0];
@@ -57,18 +70,8 @@ uint2 USART::data() {
   return (data2 << 1) | (data1 << 0);
 }
 
-//SNES -> USART
+//latch
 void USART::latch(bool data) {
-  if(txlength == 0 && latched == 1 && data == 0) {
-    txlength++;
-  } else if(txlength <= 8) {
-    txdata = (data << 7) | (txdata >> 1);
-    txlength++;
-  } else {
-    if(data == 1) txbuffer.append(txdata);
-    txlength = 0;
-  }
-
   latched = data;
 }
 
@@ -85,8 +88,9 @@ USART::USART(bool port) : Controller(port) {
 
   string filename = interface->path(Cartridge::Slot::Base, "usart.so");
   if(open_absolute(filename)) {
+    init = sym("usart_init");
     main = sym("usart_main");
-    if(main) create(Controller::Enter, 1000000);
+    if(init && main) create(Controller::Enter, 1000000);
   }
 }
 

bsnes/snes/controller/usart/usart.hpp

@@ -23,5 +23,6 @@ private:
   uint8 txdata;
   vector<uint8> txbuffer;
 
-  function<void (function<void (unsigned)>, function<uint8 ()>, function<void (uint8)>)> main;
+  function<void (function<void (unsigned)>, function<uint8 ()>, function<void (uint8)>)> init;
+  function<void ()> main;
 };