stm32/uart: Always show the flow setting when printing a UART object.

Also change the order of printing of flow so it is after stop (so bits,
parity, stop are one after the other), and reduce code size by using
mp_print_str instead of mp_printf where possible.

See issue #1981.

ports/stm32/uart.c

@@ -587,20 +587,27 @@ STATIC void pyb_uart_print(const mp_print_t *print, mp_obj_t self_in, mp_print_k
             self->uart_id, self->uart.Init.BaudRate, bits);
         if (self->uart.Init.Parity == UART_PARITY_NONE) {
             mp_print_str(print, "None");
+        } else if (self->uart.Init.Parity == UART_PARITY_EVEN) {
+            mp_print_str(print, "0");
         } else {
-            mp_printf(print, "%u", self->uart.Init.Parity == UART_PARITY_EVEN ? 0 : 1);
+            mp_print_str(print, "1");
         }
-        if (self->uart.Init.HwFlowCtl) {
-            mp_printf(print, ", flow=");
+        mp_printf(print, ", stop=%u, flow=",
+            self->uart.Init.StopBits == UART_STOPBITS_1 ? 1 : 2);
+        if (self->uart.Init.HwFlowCtl == UART_HWCONTROL_NONE) {
+            mp_print_str(print, "0");
+        } else {
             if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_RTS) {
-                mp_printf(print, "RTS%s", self->uart.Init.HwFlowCtl & UART_HWCONTROL_CTS ? "|" : "");
+                mp_print_str(print, "RTS");
+                if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_CTS) {
+                   mp_print_str(print, "|");
+                }
             }
             if (self->uart.Init.HwFlowCtl & UART_HWCONTROL_CTS) {
-                mp_printf(print, "CTS");
+                mp_print_str(print, "CTS");
             }
         }
-        mp_printf(print, ", stop=%u, timeout=%u, timeout_char=%u, read_buf_len=%u)",
-            self->uart.Init.StopBits == UART_STOPBITS_1 ? 1 : 2,
+        mp_printf(print, ", timeout=%u, timeout_char=%u, read_buf_len=%u)",
             self->timeout, self->timeout_char,
             self->read_buf_len == 0 ? 0 : self->read_buf_len - 1); // -1 to adjust for usable length of buffer
     }

tests/pyb/uart.py.exp

@@ -12,8 +12,8 @@ UART XB
 UART YA
 UART YB
 ValueError Z
-UART(1, baudrate=9600, bits=8, parity=None, stop=1, timeout=1000, timeout_char=3, read_buf_len=64)
-UART(1, baudrate=2400, bits=8, parity=None, stop=1, timeout=1000, timeout_char=7, read_buf_len=64)
+UART(1, baudrate=9600, bits=8, parity=None, stop=1, flow=0, timeout=1000, timeout_char=3, read_buf_len=64)
+UART(1, baudrate=2400, bits=8, parity=None, stop=1, flow=0, timeout=1000, timeout_char=7, read_buf_len=64)
 0
 3
 4