boards/olimex-msp430-h1611: uart_stdio @ 9600 Bd

maribu · maribu · commit 407deabc0fdb · 2024-01-22T16:59:23.000+01:00
diff --git a/boards/olimex-msp430-h1611/Makefile.include b/boards/olimex-msp430-h1611/Makefile.include
@@ -1,3 +1,9 @@
+# UART @ 115200 Bd is not reliable with a CPU clock of ~ 5 MHz, occasionally
+# chars get lost. Adding an 8 MHz crystal or an external resistor so that the
+# DCO can reach 8 MHz does yield the speed bump needed for a more reliable
+# UART connection @ 115200 Bd
+BAUD                    ?= 9600
+
 # When freshly plugged in the Olimex MSP430-JTAG-Tiny debugger provides a
 # ttyACM interface, which is only available until the first flashing. A
 # `make term` or even a `make flash term` may pick the JTAG debugger instead
@@ -16,3 +22,4 @@ TTY_SELECT_CMD := $(RIOTTOOLS)/usb-serial/ttys.py \
                   --format path serial
 
 include $(RIOTBOARD)/common/msp430/Makefile.include
+CFLAGS += -DSTDIO_UART_BAUDRATE=$(BAUD)
diff --git a/boards/olimex-msp430-h1611/include/periph_conf.h b/boards/olimex-msp430-h1611/include/periph_conf.h
@@ -35,6 +35,10 @@ extern "C" {
  * @brief   Clock configuration
  */
 static const msp430_clock_params_t clock_params = {
+    /* Without an external resistor, the DCO frequency typically tops out
+     * at something like 5 MHz. However, the DCO calibration just picks the
+     * closet possible value, in this case it will go for the highest frequency
+     * the silicon at hand can run at. */
     .target_dco_frequency = MHZ(8),
     .lfxt1_frequency = 32768,
     .main_clock_source = MAIN_CLOCK_SOURCE_DCOCLK,
