uart: Added logic to regulate data rate

Now uses a data rate thst is proportional to speed.
Could be made a bit better by using the cycle clock count directly,
but this method is a bit clearer

Signed-off-by: Michel Pollet <buserror@gmail.com>

diff --git a/simavr/sim/avr_uart.c b/simavr/sim/avr_uart.c
index f6000e6..7cb019a 100644 (file)
--- a/simavr/sim/avr_uart.c
+++ b/simavr/sim/avr_uart.c
@@ -97,8 +97,9 @@ static uint8_t avr_uart_read(struct avr_t * avr, avr_io_addr_t addr, void * para
        // made to trigger potential watchpoints
        v = avr_core_watch_read(avr, addr);
 
-       if (!uart_fifo_isempty(&p->input))
-               avr_cycle_timer_register_usec(avr, 100, avr_uart_rxc_raise, p); // should be uart speed dependent
+       // should always trigger that timer
+//     if (!uart_fifo_isempty(&p->input))
+       avr_cycle_timer_register_usec(avr, p->usec_per_byte, avr_uart_rxc_raise, p);
 
        return v;
 }
@@ -113,7 +114,17 @@ static void avr_uart_baud_write(struct avr_t * avr, avr_io_addr_t addr, uint8_t
                baud /= 8;
        else
                baud /= 16;
-       printf("UART-%c configured to %04x = %d baud\n", p->name, val, baud);
+
+       const int databits[] = { 5,6,7,8,  /* 'reserved', assume 8 */8,8,8, 9 };
+       int db = databits[avr_regbit_get(avr, p->ucsz) | (avr_regbit_get(avr, p->ucsz2) << 2)];
+       int sb = 1 + avr_regbit_get(avr, p->usbs);
+       int word_size = 1 /* start */ + db /* data bits */ + 1 /* parity */ + sb /* stops */;
+
+       printf("UART-%c configured to %04x = %d bps, %d data %d stop\n",
+                       p->name, val, baud, db, sb);
+       // TODO: Use the divider value and calculate the straight number of cycles
+       p->usec_per_byte = 1000000 / (baud / word_size);
+       printf("Roughtly %d usec per bytes\n", (int)p->usec_per_byte);
 }
 
 static void avr_uart_write(struct avr_t * avr, avr_io_addr_t addr, uint8_t v, void * param)
@@ -124,7 +135,8 @@ static void avr_uart_write(struct avr_t * avr, avr_io_addr_t addr, uint8_t v, vo
                avr_core_watch_write(avr, addr, v);
 
                avr_regbit_clear(avr, p->udrc.raised);
-               avr_cycle_timer_register_usec(avr, 100, avr_uart_txc_raise, p); // should be uart speed dependent
+               avr_cycle_timer_register_usec(avr,
+                               p->usec_per_byte, avr_uart_txc_raise, p); // should be uart speed dependent
 
                if (p->flags & AVR_UART_FLAG_STDIO) {
                        static char buf[128];
@@ -180,7 +192,7 @@ static void avr_uart_irq_input(struct avr_irq_t * irq, uint32_t value, void * pa
                return;
 
        if (uart_fifo_isempty(&p->input))
-               avr_cycle_timer_register_usec(avr, 100, avr_uart_rxc_raise, p); // should be uart speed dependent
+               avr_cycle_timer_register_usec(avr, p->usec_per_byte, avr_uart_rxc_raise, p); // should be uart speed dependent
        uart_fifo_write(&p->input, value); // add to fifo
 
 //     printf("UART IRQ in %02x (%d/%d) %s\n", value, p->input.read, p->input.write, uart_fifo_isfull(&p->input) ? "FULL!!" : "");
@@ -201,7 +213,7 @@ void avr_uart_reset(struct avr_io_t *io)
 
        // DEBUG allow printf without fidding with enabling the uart
        avr_regbit_set(avr, p->txen);
-
+       p->usec_per_byte = 100;
 }
 
 static int avr_uart_ioctl(struct avr_io_t * port, uint32_t ctl, void * io_param)

diff --git a/simavr/sim/avr_uart.h b/simavr/sim/avr_uart.h
index 4764e72..dc9e805 100644 (file)
--- a/simavr/sim/avr_uart.h
+++ b/simavr/sim/avr_uart.h
@@ -92,6 +92,9 @@ typedef struct avr_uart_t {
        avr_regbit_t    rxen;           // receive enabled
        avr_regbit_t    txen;           // transmit enable
        avr_regbit_t    u2x;            // double UART speed
+       avr_regbit_t    usbs;           // stop bits
+       avr_regbit_t    ucsz;           // data bits
+       avr_regbit_t    ucsz2;          // data bits, continued
 
        avr_io_addr_t r_ubrrl,r_ubrrh;
 
@@ -102,6 +105,7 @@ typedef struct avr_uart_t {
        uart_fifo_t     input;
 
        uint32_t                flags;
+       avr_cycle_count_t usec_per_byte;
 } avr_uart_t;
 
 /* takes a uint32_t* as parameter */