# Send a single pulse low/high pulse then stay high

I have a small OLED display that I'd like to drive with an ATtiny85 micro controller. The OLED is the 4 wire SPI type, with no CS. It has a Reset pin that is required to be pulsed low-high at power on and then kept high for normal operation.

This seems like a waste of a pin - I want to be able to do other things with the MC.

simulate this circuit – Schematic created using CircuitLab

Is there a way I can generate the required pulse without using a MC pin?

Power On sequence, as stated in the data sheet:

with RES# being the one I want to avoid using a pin for.

Thanks

• You'd need to post a schematic of your layout and thinking. There's a schematic button on the editor toolbar. – Transistor Apr 7 '18 at 21:18
• Can you manipulate MOSI output state or transition to trigger a 1 shot to replace SS enable for desired interval? – Sunnyskyguy EE75 Apr 7 '18 at 21:55
• Welcome to the site. Please can you edit your question to show a schematic (not a block diagram or wiring diagram). The schematic editor here is a breeze to use. The better the quality of question, the better the quality of the answers you will attract. Again, a warm welcome to the site. – TonyM Apr 7 '18 at 21:56
• I don't think I can use MOSI because I'll need that to transmit display information later and if RES# is pulsed again it'll re-reset the display controller. – MalphasWats Apr 8 '18 at 0:12

1. connect directly RES# pin to VDD (although this is not recommended, I see this in some applications and it is working)
• 100nF between RES# and GND
• 10kOhm between RES# and VDD
• one diode from RES# to VDD
• I have tried connecting RES# and Vcc, however, this doesn't work, the screen sometimes displays garbage and sometimes just stays blank. If I connect RES# to Reset on the ATtiny it works perfectly if I ground Reset momentarily, however, it doesn't work properly on first power up (power up then reset works ok, but is sub-optimal). I will try option 3 when I get a chance! – MalphasWats Apr 8 '18 at 13:40
• Option 3 does indeed appear to work for first power on, however, it produced the same behaviour if connected to Reset on the ATtiny - it displays garbage on power on but works after a reset pulse to both. A diode between RES# and Reset appears to have done the trick! Thank you. – MalphasWats Apr 8 '18 at 13:59