Adds service requests. The microcontroller now appears to consume keyboard events.

Machines/Apple/ADB/Bus.cpp

@@ -50,6 +50,7 @@ void Bus::set_device_output(size_t device_id, bool output) {
 					device->adb_bus_did_observe_event(Event::Attention);
 				}
 				shift_register_ = 1;
+				start_target_ = 9;		// Consume the stop bit before posting the next byte.
 				phase_ = Phase::AttentionCapture;
 			} else if(low_microseconds < 50.0) {
 				shift(1);
@@ -73,15 +74,18 @@ void Bus::set_device_output(size_t device_id, bool output) {
 void Bus::shift(unsigned int value) {
 	shift_register_ = (shift_register_ << 1) | value;
 
-	// Trigger a byte whenever a start bit hits bit 8.
-	if(shift_register_ & 0x100) {
+	// Trigger a byte whenever either:
+	//	* a 'start bit' hits bit 8; or
+	//	* if this was a command byte, wait for the stop bit (i.e. the start bit hits 9).
+	if(shift_register_ & (1 << start_target_)) {
 		for(auto device: devices_) {
-			device->adb_bus_did_observe_event(Event::Byte, uint8_t(shift_register_));
+			device->adb_bus_did_observe_event(Event::Byte, uint8_t(shift_register_ >> (start_target_ - 8)));
 		}
 
 		// Expect a real start bit only if moving from attention capture to packet
 		// capture. Otherwise adopt an implied start bit.
 		shift_register_ = phase_ == Phase::PacketCapture;
+		start_target_ = 8;
 		phase_ = Phase::PacketCapture;
 	}
 }

Machines/Apple/ADB/Bus.hpp

@@ -151,6 +151,7 @@ class Bus {
 		double half_cycles_to_microseconds_ = 1.0;
 		std::vector<Device *> devices_;
 		unsigned int shift_register_ = 0;
+		unsigned int start_target_ = 8;
 		bool data_level_ = true;
 
 		// ADB addressing supports at most 16 devices but that doesn't include

Machines/Apple/ADB/Keyboard.cpp

@@ -132,6 +132,8 @@ bool Keyboard::set_key_pressed(Key key, bool is_pressed) {
 	}
 #undef SetModifierBit
 
+	// Ensure service occurs.
+	post_service_request();
 	return true;
 }
 
@@ -144,6 +146,7 @@ void Keyboard::clear_all_keys() {
 			pressed_keys_[key] = false;
 		}
 	}
+	if(!pending_events_.empty()) post_service_request();
 
 	// Mark all modifiers as released.
 	modifiers_ |= 0xfff8;

Machines/Apple/ADB/ReactiveDevice.cpp

@@ -27,6 +27,18 @@ void ReactiveDevice::post_response(const std::vector<uint8_t> &&response) {
 }
 
 void ReactiveDevice::advance_state(double microseconds, bool current_level) {
+	// First test: is a service request desired?
+	if(phase_ == Phase::ServiceRequestPending) {
+		microseconds_at_bit_ += microseconds;
+		if(microseconds_at_bit_ < 240.0) {
+			bus_.set_device_output(device_id_, false);
+		} else {
+			bus_.set_device_output(device_id_, true);
+			phase_ = Phase::AwaitingAttention;
+		}
+		return;
+	}
+
 	// Do nothing if not in the process of posting a response.
 	if(response_.empty()) return;
 
@@ -50,10 +62,10 @@ void ReactiveDevice::advance_state(double microseconds, bool current_level) {
 
 	// If this is the start of the packet, wait an appropriate stop-to-start time.
 	if(bit_offset_ == -2) {
-		if(microseconds_at_bit_ < 250.0) {
+		if(microseconds_at_bit_ < 150.0) {
 			return;
 		}
-		microseconds_at_bit_ -= 250.0;
+		microseconds_at_bit_ -= 150.0;
 		++bit_offset_;
 	}
 
@@ -115,8 +127,15 @@ void ReactiveDevice::adb_bus_did_observe_event(Bus::Event event, uint8_t value)
 		command_ = decode_command(value);
 		LOG(command_);
 
-		// Don't do anything if this command isn't relevant here.
+		// If this command doesn't apply here, but a service request is requested,
+		// post a service request.
 		if(command_.device != Command::AllDevices && command_.device != ((register3_ >> 8) & 0xf)) {
+			if(service_desired_) {
+				service_desired_ = false;
+				stop_has_begin_ = false;
+				phase_ = Phase::ServiceRequestPending;
+				microseconds_at_bit_ = 0.0;
+			}
 			return;
 		}
 
@@ -138,6 +157,7 @@ void ReactiveDevice::adb_bus_did_observe_event(Bus::Event event, uint8_t value)
 						receive_bytes(2);
 					}
 				} else {
+					service_desired_ = false;
 					perform_command(command_);
 				}
 			break;
@@ -156,5 +176,5 @@ void ReactiveDevice::reset() {
 }
 
 void ReactiveDevice::post_service_request() {
-	// TODO.
+	service_desired_ = true;
 }

Machines/Apple/ADB/ReactiveDevice.hpp

@@ -11,6 +11,7 @@
 
 #include "Bus.hpp"
 
+#include <atomic>
 #include <cstddef>
 #include <vector>
 
@@ -44,14 +45,18 @@ class ReactiveDevice: public Bus::Device {
 			AwaitingAttention,
 			AwaitingCommand,
 			AwaitingContent,
+			ServiceRequestPending,
 		} phase_ = Phase::AwaitingAttention;
 		std::vector<uint8_t> content_;
 		size_t expected_content_size_ = 0;
 		Command command_;
+		bool stop_has_begin_ = false;
 
 		uint16_t register3_;
 		const uint8_t default_adb_device_id_;
 
+		std::atomic<bool> service_desired_ = false;
+
 		void reset();
 };