All,
If this is not in the correct forum, please excuse my ignorance. If not, then please read further.
I have purchased a few NewHaven Display 4 x 20 LCD's that are I2C, SPI & TTL serial capable.
I will eventually use a Teensy 3.2 to communicate using the Serial method to the LCD.
My problem... I found out after the fact that the TTL levels do not meet the 3.3v output levels. In the electrical specifications for the LCD below, you can see the voltage levels are NG (0.70 * VDD of 5.0v) = 3.5v
So, the only option is to make a logic level up shifter, but, there are so many options to choose from. Note that my limitation is that I have is that I do NOT have a 3.3v source, only 5 Volts from the external LM7805. Why no 3.3v? The Teensy 3.2 onboard regulator is being used to power an Nrf wireless module. This is where I need help.
From a hardware aspect, I can use a simple schematic below...
with 5v tolerant pins on the Teensy 3.2 being a benefit, but I don't think that the circuit will work when pulling logic low. Will it get me close to Vss or 0.6v?
Another alternative is to use a SN7407...
and last is using FETs which will require 2, 3.3v + 5v and inverse the logic which will require two. This option I do not care for because there's allot of traces and thru hole mounting.
So, I would like to ask the group... could schematic 1 work? opinions of schematic 2, and trying my best to stay away from the FET option. What other simple schematics, transistors options could I use that would give me ...
1. The non inverse logic problem
2. will work with 5v only
3. has less 9 holes to mount.
Can you please share schematics that can work other than what I have given.
Thanks
BLMinTenn
If this is not in the correct forum, please excuse my ignorance. If not, then please read further.
I have purchased a few NewHaven Display 4 x 20 LCD's that are I2C, SPI & TTL serial capable.
I will eventually use a Teensy 3.2 to communicate using the Serial method to the LCD.
My problem... I found out after the fact that the TTL levels do not meet the 3.3v output levels. In the electrical specifications for the LCD below, you can see the voltage levels are NG (0.70 * VDD of 5.0v) = 3.5v
So, the only option is to make a logic level up shifter, but, there are so many options to choose from. Note that my limitation is that I have is that I do NOT have a 3.3v source, only 5 Volts from the external LM7805. Why no 3.3v? The Teensy 3.2 onboard regulator is being used to power an Nrf wireless module. This is where I need help.
From a hardware aspect, I can use a simple schematic below...
with 5v tolerant pins on the Teensy 3.2 being a benefit, but I don't think that the circuit will work when pulling logic low. Will it get me close to Vss or 0.6v?
Another alternative is to use a SN7407...
and last is using FETs which will require 2, 3.3v + 5v and inverse the logic which will require two. This option I do not care for because there's allot of traces and thru hole mounting.
So, I would like to ask the group... could schematic 1 work? opinions of schematic 2, and trying my best to stay away from the FET option. What other simple schematics, transistors options could I use that would give me ...
1. The non inverse logic problem
2. will work with 5v only
3. has less 9 holes to mount.
Can you please share schematics that can work other than what I have given.
Thanks
BLMinTenn