Sparkfun OLED breakout I2C comm needs advice please

[vibnwis]

HI there,

I am working on Sparkfun OLED breakout through I2C. I setup the jumpers as recommended (see pic), and I always failed on
espRc = i2c_master_cmd_begin(I2C_NUM_1, cmd, 100/portTICK_PERIOD_MS);

Yes, I used I2C_NUM_1. HOwever, I had also tried on I2C_NUM_0 as well, it failed with the same error. The device addresss is 0x3C, however, I had also tried on 0x3D just in case it jumper does not. NOthing seems to be working on this breakout. I measured it Vcc is 3.0V. I am going to try using external power supply. Other than that, I am running out of idea. Any advise, please?

From the waveforms, it looks like, the device is not responding. Any idea how to check it is dead?

Thank you
Lim

[vibnwis]

I did not connect nRST line as suggested. My bad. Having connected to a GPIO, and set it Low-then-HIgh, it works now.

Cheers!