add serial interface and a few std library functions

changes in usart:
  - new functions to setup the serial comunication settings such as baudrate,
    parity and stop bits
  - init function with most common values
  - transmit and receive functions each with a wrapper to send data blocks

changes in libc:
  - new file stdio.c with basic implementation of putch, printf still a prototype
  - new file string.c with memcpy() function

4 files changed, 170 insertions, 88 deletions

diff --git a/sw/z80/kernel/include/devices.h b/sw/z80/kernel/include/devices.h
index ea29065..e8c183f 100644
--- a/sw/z80/kernel/include/devices.h
+++ b/sw/z80/kernel/include/devices.h
@@ -4,9 +4,9 @@
 #define ADDR_DEV_ROM_L      0x0000
 #define ADDR_DEV_ROM_H      0x2000
 
-#define ADDR_DEV_USART   0x4000
-#define ADDR_DEV_CTC     
-#define ADDR_DEV_PIO
+#define ADDR_DEV_USART      0x4000
+#define ADDR_DEV_CTC        0x4100
+#define ADDR_DEV_PIO        0x4200
 
 #define ADDR_DEV_RAM        0x8000
 
diff --git a/sw/z80/kernel/include/pio.h b/sw/z80/kernel/include/pio.h
new file mode 100644
index 0000000..8d72ab0
--- /dev/null
+++ b/sw/z80/kernel/include/pio.h
@@ -0,0 +1,18 @@
+#ifndef __PIO_H__
+#define __PIO_H__
+
+#define PIO_A   0
+#define PIO_B   1
+
+
+void pio_data(int port, uint8_t data);
+void pio_command(int port, uint8_t cmd);
+
+uint8_t pio_read_data(int port);
+
+inline int pio_read_pin(int port, uint8_t pin);
+inline void pio_write_pin(int port, uint8_t pin);
+
+// TODO: implement mode (in/out/both) and interrupt vector
+
+#endif // __PIO_H__
diff --git a/sw/z80/kernel/include/serial.h b/sw/z80/kernel/include/serial.h
deleted file mode 100644
index 03e2448..0000000
--- a/sw/z80/kernel/include/serial.h
+++ /dev/null
@@ -1,85 +0,0 @@
-#ifndef __SERIAL_H__
-#define __SERIAL_H__
-
-#include "types.h"
-#include "devices.h"
-
-/* this structure is only for internal usage */
-struct _usart_device
-{
-    register_t buffer;  // also used as LSB for divisor latch
-
-    struct IER 
-    {
-        volatile int received_data_interrupt :1;
-        volatile int transmitter_empty_interrupt :1;
-        volatile int receiver_line_status_interrupt :1;
-        volatile int modem_status_interrupt :1;
-            volatile int reserved :4;
-    } IER;
-
-    struct IIR
-    {
-        volatile int interrupt_pending :1;
-        volatile int interrupt_id :3;
-        volatile int reserved :2;
-        volatile int fifos :2;
-    } IIR;
-
-    struct FCR
-    {
-        volatile int fifo_enable :1;
-        volatile int receiver_fifo_rst :1;
-    }
-
-    struct LCR
-    {
-        volatile int word_length :2;
-        volatile int stop_bits :1;
-        volatile int parity :1;
-        volatile int even_parity :1;
-        volatile int stick_parity :1;
-        volatile int break_control :1;
-        volatile int divisor_latch_access :1;
-    } LCR;
-
-    struct MCR
-    {
-        volatile int data_terminal_ready :1;
-        volatile int request_to_send :1;
-        volatile int out1;
-        volatile int out2;
-        volatile int loop;
-        volatile int autoflow :1;
-        volatile int reserved :2;
-    } MCR;
-
-    struct LSR 
-    {
-        volatile int data_ready :1;
-        volatile int overrun_error :1;
-        volatile int parity_error :1;
-        volatile int framing_error :1;
-        volatile int break_interrupt :1;
-        volatile int transmitter_register :1;
-        volatile int transmitter_emtpy :1;
-        volatile int fifo_recv_error :1;
-    } LSR;
-
-    struct MSR
-    {
-        volatile int delta_cts :1;
-        volatile int delta_data_set_ready :1;
-        volatile int trailing_edge_ring_indicator :1;
-        volatile int delta_data_carrier_detect :1;
-        volatile int clear_to_send :1;
-        volatile int data_set_ready :1;
-        volatile int ring_indicator :1;
-        volatile int data_carrier_detect :1;
-    } MSR;
-
-    register_t scratch;
-} *_usart = (_usart_device *) ADDR_DEV_USART;
-
-
-#endif // __SERIAL__H__
diff --git a/sw/z80/kernel/include/usart.h b/sw/z80/kernel/include/usart.h
new file mode 100644
index 0000000..f1f428e
--- /dev/null
+++ b/sw/z80/kernel/include/usart.h
@@ -0,0 +1,149 @@
+#ifndef __USART_H__
+#define __USART_H__
+
+#include "types.h"
+#include "devices.h"
+
+#include "string.h"
+
+// baudrate clock divisors 
+// values from TL16C550C datasheet (table 9 for 1.8432 MHz crystal)
+#define USART_BAUDRATE_50       2304
+#define USART_BAUDRATE_75       1536
+#define USART_BAUDRATE_110      1047
+#define USART_BAUDRATE_134_5    857
+#define USART_BAUDRATE_150      768
+#define USART_BAUDRATE_300      384
+#define USART_BAUDRATE_600      192
+#define USART_BAUDRATE_1200     96
+#define USART_BAUDRATE_1800     64
+#define USART_BAUDRATE_2000     58
+#define USART_BAUDRATE_2400     48
+#define USART_BAUDRATE_3600     32
+#define USART_BAUDRATE_4800     24
+#define USART_BAUDRATE_7200     16
+#define USART_BAUDRATE_9600     12
+#define USART_BAUDRATE_19200    6
+#define USART_BAUDRATE_38400    3
+#define USART_BAUDRATE_56000    3
+
+// parity
+#define USART_PARITY_NONE       0
+#define USART_PARITY_EVEN       1
+#define USART_PARITY_ODD        2
+
+// stop bits
+#define USART_STOP_BITS_1       10
+#define USART_STOP_BITS_15      15
+#define USART_STOP_BITS_2       20
+
+// word lenght
+#define USART_WORD_LENGTH_5     0
+#define USART_WORD_LENGTH_6     1
+#define USART_WORD_LENGTH_7     2
+#define USART_WORD_LENGTH_8     3
+
+// autoflow
+#define USART_AUTOFLOW_ALL      3
+#define USART_AUTOFLOW_CTS      2
+#define USART_AUTOFLOW_OFF      0
+
+
+/* this structure is only for internal usage */
+struct _usart_device
+{
+    register_t buffer;  // also used as LSB for divisor latch
+
+    struct IER 
+    {
+        volatile int received_data_interrupt :1;
+        volatile int transmitter_empty_interrupt :1;
+        volatile int receiver_line_status_interrupt :1;
+        volatile int modem_status_interrupt :1;
+        volatile int reserved :4;
+    } IER;
+
+    struct IIR
+    {
+        volatile int interrupt_pending :1;
+        volatile int interrupt_id :3;
+        volatile int reserved :2;
+        volatile int fifos :2;
+    } IIR;
+
+    struct FCR
+    {
+        volatile int fifo_enable :1;
+        volatile int receiver_fifo_rst :1;
+        volatile int trasmitter_fifo_rst :1;
+        volatile int dma_mode_select :1;
+        volatile int reserved :1;
+        volatile int receiver_trigger :2;
+    } FCR;
+
+    struct LCR
+    {
+        volatile int word_length :2;
+        volatile int stop_bits :1;
+        volatile int parity :1;
+        volatile int even_parity :1;
+        volatile int stick_parity :1;
+        volatile int break_control :1;
+        volatile int divisor_latch_access :1;
+    } LCR;
+
+    struct MCR
+    {
+        volatile int data_terminal_ready :1;
+        volatile int request_to_send :1;
+        volatile int out1;
+        volatile int out2;
+        volatile int loop;
+        volatile int autoflow :1;
+        volatile int reserved :2;
+    } MCR;
+
+    struct LSR 
+    {
+        volatile int data_ready :1;
+        volatile int overrun_error :1;
+        volatile int parity_error :1;
+        volatile int framing_error :1;
+        volatile int break_interrupt :1;
+        volatile int transmitter_holder_empty :1;
+        volatile int transmitter_empty :1;
+        volatile int fifo_recv_error :1;
+    } LSR;
+
+    struct MSR
+    {
+        volatile int delta_cts :1;
+        volatile int delta_data_set_ready :1;
+        volatile int trailing_edge_ring_indicator :1;
+        volatile int delta_data_carrier_detect :1;
+        volatile int clear_to_send :1;
+        volatile int data_set_ready :1;
+        volatile int ring_indicator :1;
+        volatile int data_carrier_detect :1;
+    } MSR;
+
+    register_t scratch;
+};
+
+
+// setup functions (wrappers)
+void usart_set_baudrate(uint16_t baudrate);
+void usart_set_parity(int mode);
+void usart_set_stob_bits(int count);
+void usart_set_word_length(int length);
+void usart_set_autoflow(int mode);
+
+inline void usart_init(uint16_t baudrate, int parity, int stop_bits); 
+
+void usart_transmit(uint8_t data);
+uint8_t usart_receive();
+
+int usart_write(uint8_t *data, size_t size);
+int usart_read(uint8_t *buffer, size_t count);
+
+#endif // __USART__H__