First, thank you very much for developing this tool. It works great most of the time, and is orders of magnitude faster than OpenOCD for programming STM32 microcontrollers.

One issue I ran across is that st-flash does not seem to work when my CPU (stm32l031k6) is in stop mode. A workaround that I found is to press and release the reset button at exactly the same time as running the st-flash command; this doesn't work every time though.

I am on Linux (Ubuntu Trusty), have fresh st-flash (compiled from the latest snapshot in git), and am using a Nucleo STM32L031 board. I can attach a simple bin file that demonstrates the problem if it's helpful.

The command that I use is

st-flash --reset write bin/test.bin 0x8000000

The output that I get is

2016-06-06T12:39:08 INFO src/common.c: Loading device parameters....
2016-06-06T12:39:08 WARN src/common.c: unknown chip id! 0

but only if the CPU is in stop mode. Otherwise everything works as expected.

Apologies if this is a known issue and I haven't done enough searching to find it.