I have been testing USB to TTL converters based on different chips, coming from ebay.
I have found a different response in 1.5.8 with respect to 1.5.6 or 1.5.4 for the SiLabs CP2102 board.
I have three of these boards (B1,B2,B3), all of them with RTS pin.
I make the test with two macbook pro.
setting : macbookpro I7 LIon 10.7.5 and retina Mavericks 10.9.5 both with cu.SLAB_USBtoUART
Only one of them (say B3 is able to upload auomatically on a
arduino pro mini (Atmega328 5V 16Mhz).
But I can upload with B1 and B2 with manual reset.
B3 can upload again automatically,
but B1 and B2 can no longer upload, even in manual mode.
Is this issue known ?