1 files changed, 91 insertions, 0 deletions
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;
+}