In an attempt to clarify the above partial schematic, I have created this minimum working solution in SimulIDE. Hopefully it shows the essential connections a little more clearly.
Cheers
Chris
EDIT: Fixed error Q6 now connects to D7
Last edit: Chris Roper 2020-09-15
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Well done Chris, I'm sure this would be a great benefit to many. I tried to find an updated version of lcd.h which might have the software so I could check it out, but without luck - are you able to help ?
One thing that intrigued me was the choice of 74LS574 as opposed to a 74HC595. The extra wiring ( 8 outputs to 8 inputs) and cost (74HC595 are very popular and consequently cheap!) . To achieve the same thing on a 595 all you have to do is tie the two clocks (input & latch) together and
supply 9 clock pulses. The Data output pin is shared between the 595 datain and RS pin on the LCD. After the 9 clock pulses + a short delay the RS state is set, the Enable Pin is made High - which latches in the RS status on the rising edge and on the falling edge of the clock latches in the lcd data.
Regards, Geoff
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
The Files are in the Build queue awaiting release when documentation is complete.
Anobium is on the Road at the moment but is planning to release in a few days.
The choice of 74LS574 was not mine, I just needed a driver for it as it was used in a Brazilian made training board and is simulated in PICSimLab as Board 2.
I was, still am, considering using PICSimLab as a tutorial platform for GCBASIC and as such needed to be able to drive that LCD, hence the new driver.
For the reasons you give I doubt that this configuration will be used in any new designs, but it is an interesting exercise. Note that in terms of a PCB layout the majority of the connections are pin to pin under the actual device, so a very simple, neat and compact footprint.
Cheers
Chris
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Just added LCD_IO 3. A new method to connect an LCD. See http://gcbasic.sourceforge.net/help/_lcd_io_3.html
But, essentially a three port connection with Data, Clock and Enable lines connected to LS74574.
Chris Roper is using this new method in his PICSim demonstrations.
Enjoy.
In an attempt to clarify the above partial schematic, I have created this minimum working solution in SimulIDE. Hopefully it shows the essential connections a little more clearly.
Cheers
Chris
EDIT: Fixed error Q6 now connects to D7
Last edit: Chris Roper 2020-09-15
Well done Chris, I'm sure this would be a great benefit to many. I tried to find an updated version of lcd.h which might have the software so I could check it out, but without luck - are you able to help ?
One thing that intrigued me was the choice of 74LS574 as opposed to a 74HC595. The extra wiring ( 8 outputs to 8 inputs) and cost (74HC595 are very popular and consequently cheap!) . To achieve the same thing on a 595 all you have to do is tie the two clocks (input & latch) together and
supply 9 clock pulses. The Data output pin is shared between the 595 datain and RS pin on the LCD. After the 9 clock pulses + a short delay the RS state is set, the Enable Pin is made High - which latches in the RS status on the rising edge and on the falling edge of the clock latches in the lcd data.
Regards, Geoff
Hi Geoff,
The Files are in the Build queue awaiting release when documentation is complete.
Anobium is on the Road at the moment but is planning to release in a few days.
The choice of 74LS574 was not mine, I just needed a driver for it as it was used in a Brazilian made training board and is simulated in PICSimLab as Board 2.
I was, still am, considering using PICSimLab as a tutorial platform for GCBASIC and as such needed to be able to drive that LCD, hence the new driver.
For the reasons you give I doubt that this configuration will be used in any new designs, but it is an interesting exercise. Note that in terms of a PCB layout the majority of the connections are pin to pin under the actual device, so a very simple, neat and compact footprint.
Cheers
Chris