Esptool RTS signal polarity
Posted: Wed Oct 26, 2016 9:43 amThe connect() function in esptool is as follows:
It obviously works, but I'm at a loss trying to understand why.
It sets RTS, waits a bit, then clears RTS line, thus putting ESP to reset. At least it should do so, based on the source of esptool and the fact that ESP is held in reset by low level on that line.
Can anyone please explain why does this code work?
Code: Select all
""" Try connecting repeatedly until successful, or giving up """
def connect(self):
print 'Connecting...'
for _ in xrange(4):
# issue reset-to-bootloader:
# RTS = either CH_PD or nRESET (both active low = chip in reset)
# DTR = GPIO0 (active low = boot to flasher)
self._port.setDTR(False)
self._port.setRTS(True)
time.sleep(0.05)
self._port.setDTR(True)
self._port.setRTS(False)
time.sleep(0.05)
self._port.setDTR(False)
# worst-case latency timer should be 255ms (probably <20ms)
self._port.timeout = 0.3
for _ in xrange(4):
try:
self._port.flushInput()
self._slip_reader = slip_reader(self._port)
self._port.flushOutput()
self.sync()
self._port.timeout = 5
return
except:
time.sleep(0.05)
raise FatalError('Failed to connect to ESP8266')
It obviously works, but I'm at a loss trying to understand why.
It sets RTS, waits a bit, then clears RTS line, thus putting ESP to reset. At least it should do so, based on the source of esptool and the fact that ESP is held in reset by low level on that line.
Can anyone please explain why does this code work?