Sleep until USB port becomes writable before running avrdude (#5393)

* sleep until usb port becomes writable before running avrdude

* only wait for a writable USB port when not on MSYS

using MINGW or MSYS: sleep for one second, as before.

otherwise: wait for the port to become writable.

* typo

* typo

1 files changed, 5 insertions, 2 deletions

diff --git a/tmk_core/avr.mk b/tmk_core/avr.mk
index d22c3bbca..79fdf4de5 100644
--- a/tmk_core/avr.mk
+++ b/tmk_core/avr.mk
@@ -214,12 +214,15 @@ define EXEC_AVRDUDE
                         mv /tmp/2 /tmp/1; \
                 done; \
                 echo ""; \
-                echo "Detected controller on USB port at $$USB"; \
+                echo "Device $$USB has appeared; assuming it is the controller."; \
                 if $(GREP) -q -s 'MINGW\|MSYS' /proc/version; then \
                         USB=`echo "$$USB" | perl -pne 's/\/dev\/ttyS(\d+)/COM.($$1+1)/e'`; \
                         echo "Remapped MSYS2 USB port to $$USB"; \
+                        sleep 1; \
+                else \
+                        printf "Waiting for $$USB to become writable."; \
+                        while [ ! -w "$$USB" ]; do sleep 0.5; printf "."; done; echo ""; \
                 fi; \
-                sleep 1; \
                 avrdude -p $(MCU) -c avr109 -P $$USB -U flash:w:$(BUILD_DIR)/$(TARGET).hex; \
         fi
 endef