Getting I2C on ESP8266 to work

Tried i2cdetect code with a OLED attached at address 0x3c and limit scan to 0x30-0x3f

Get fussy read results for adr <> 0x3c and lots of ERROR: No ACK

o no error for 0x3c - read value 65
o no catch was triggered

>echo(0);
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:
10:
20:
ERROR: No ACK
30:136
ERROR: No ACK
31:168
ERROR: No ACK
32:248
ERROR: No ACK
33:24
ERROR: No ACK
34:184
ERROR: No ACK
35:56
ERROR: No ACK
36:72
ERROR: No ACK
37:56
ERROR: No ACK
38:248
ERROR: No ACK
39:72
ERROR: No ACK
3a:40
ERROR: No ACK
3b:200
3c:65
ERROR: No ACK
3d:88
ERROR: No ACK
3e:136
ERROR: No ACK
3f:24
30: 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f
40:
50:
60:
70:
=undefined