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

7 files changed, 292 insertions, 90 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__
diff --git a/sw/z80/kernel/kernel.c b/sw/z80/kernel/kernel.c
index 3db6579..3d5aeb6 100644
--- a/sw/z80/kernel/kernel.c
+++ b/sw/z80/kernel/kernel.c
@@ -1,7 +1,7 @@
 #include "types.h"
-
+#include "usart.h"
 
 void kmain(void)
 {
-    
+    usart_init(USART_BAUDRATE_9600, USART_PARITY_EVEN, USART_STOP_BITS_1);
 }
diff --git a/sw/z80/kernel/pio.c b/sw/z80/kernel/pio.c
new file mode 100644
index 0000000..e8c7e24
--- /dev/null
+++ b/sw/z80/kernel/pio.c
@@ -0,0 +1,29 @@
+#include "pio.h"
+
+static uint8_t *pio_port_a = (uint8_t *) ADDR_DEV_PIO;
+static uint8_t *pio_port_b = (uint8_t *) ADDR_DEV_PIO + 1;
+static uint8_t *pio_ctrl_a = (uint8_t *) ADDR_DEV_PIO + 2;
+static uint8_t *pio_ctrl_b = (uint8_t *) ADDR_DEV_PIO + 3;
+
+void pio_data(int port, uint8_t data)
+{
+    if (port == PIO_A)
+        *pio_port_a = cmd;
+    else
+        *pio_port_b = cmd;
+}
+
+void pio_command(int port, uint8_t cmd)
+{
+    if (port == PIO_A)
+        *pio_ctrl_a = cmd;
+    else
+        *pio_ctrl_b = cmd;
+}
+
+
+
+inline int pio_read_pin(int port, uint8_t pin)
+{
+
+}
diff --git a/sw/z80/kernel/usart.c b/sw/z80/kernel/usart.c
new file mode 100644
index 0000000..4c2fdaf
--- /dev/null
+++ b/sw/z80/kernel/usart.c
@@ -0,0 +1,91 @@
+#include "usart.h"
+
+static struct _usart_device *_usart = (struct _usart_device *) ADDR_DEV_USART;
+
+void usart_set_baudrate(uint16_t baudrate)
+{
+    // enable latch access
+    _usart->LCR.divisor_latch_access = 1;
+    _usart->buffer = 0x00FF & baudrate; // LSBs
+    memcpy(&_usart->IER, &(baudrate >>8), 1);
+    // _usart->IER    = 0x00FF & (baudrate >> 8); // MSBs
+    _usart->LCR.divisor_latch_access = 0;
+}
+
+void usart_set_parity(int mode)
+{
+    if (mode == USART_PARITY_EVEN) {
+        _usart->LCR.even_parity = 1;
+    }
+    else if (mode == USART_PARITY_ODD) {
+        _usart->LCR.even_parity = 0;
+    }
+
+     _usart->LCR.parity = (mode == USART_PARITY_NONE) ? 0 : 1;
+}
+
+void usart_set_stop_bits(int count)
+{
+    _usart->LCR.stop_bits = (count == USART_STOP_BITS_1) ? 0 : 1;
+}
+
+void usart_word_length(int length)
+{
+    _usart->LCR.word_length = length;
+}
+
+void usart_set_autoflow(int mode)
+{
+    _usart->MCR.autoflow = (mode == USART_AUTOFLOW_OFF) ? 0 : 1;
+    _usart->MCR.data_terminal_ready = (mode == USART_AUTOFLOW_ALL);
+}
+
+inline void usart_init(uint16_t baudrate, int parity, int stop_bits)
+{
+    usart_set_baudrate(baudrate);
+    usart_set_parity(parity);
+    usart_set_stop_bits(stop_bits);
+    usart_set_autoflow(USART_AUTOFLOW_OFF);
+}
+
+void usart_transmit(uint8_t data)
+{
+    _usart->buffer = data;
+    while (_usart->LSR.transmitter_holder_empty == 0); // wait
+}
+
+uint8_t usart_receive()
+{
+    return _usart->buffer;
+}
+
+int usart_write(uint8_t *data, size_t size)
+{
+    uint8_t *dp = data;
+
+    while (size--) {
+        _usart->buffer = *(dp++);
+    }
+    while (_usart->LSR.transmitter_empty);
+
+    // TODO: do something that actually counts for sent bytes 
+    return size;
+}
+
+int usart_read(uint8_t *buffer, size_t count)
+{
+    uint8_t *bp = buffer;
+    size_t read_count = 0;
+
+    while (count--) {
+        *(bp++) = _usart->buffer;
+        // check for errors
+        if (_usart->LSR.framing_error || _usart->LSR.parity_error) {
+            bp--; // delete last byte (?)
+        } else {
+           read_count++;
+        }
+    }
+
+    return read_count;
+}