Hack a datalogger into existing design

M

mpm

Guest
Pretty sure the answer is "Yes", but let me ask it anyway....

Situation:
Need to add a datalogger to an existing design, but there are no free ports left on the microcontroller.

The microcontroller is an AT89LP51ED2. (An 8-bit, 8051 variant)
Port-0 outputs data ONLY to (3) D-Type transparent octal latches (74ACT573N), which are individually latched via some pins on Port-2 of the microcontroller.

The latches are written infrequently, and are never left un-latched in normal operation (i.e., we don't use the "transparent" feature of this part).

So....

Can I use a couple of Port-0 port pins for I2C SDA & SCL lines to connect up some parts to make a datalogger? (I'm thinking a 24C32 for the memory, and DS3231 for the RTC.)

It seems to me that as long as the 573 latches are latched with the intended data, I can then do whatever I want with the Port-0 pins (such as service a RTC & Memory datalogger).

All the voltages are OK (+5 VDC is used everywhere in this particular product).

So other than adjusting the code, is there anything I'm missing?

Thanks for looking / confirming this will work. (?)
 
On 4/11/20 9:22 AM, mpm wrote:
Pretty sure the answer is "Yes", but let me ask it anyway....

Situation:
Need to add a datalogger to an existing design, but there are no free ports left on the microcontroller.

The microcontroller is an AT89LP51ED2. (An 8-bit, 8051 variant)
Port-0 outputs data ONLY to (3) D-Type transparent octal latches (74ACT573N), which are individually latched via some pins on Port-2 of the microcontroller.

The latches are written infrequently, and are never left un-latched in normal operation (i.e., we don't use the "transparent" feature of this part).

So....

Can I use a couple of Port-0 port pins for I2C SDA & SCL lines to connect up some parts to make a datalogger? (I'm thinking a 24C32 for the memory, and DS3231 for the RTC.)

It seems to me that as long as the 573 latches are latched with the intended data, I can then do whatever I want with the Port-0 pins (such as service a RTC & Memory datalogger).

All the voltages are OK (+5 VDC is used everywhere in this particular product).

So other than adjusting the code, is there anything I'm missing?

Thanks for looking / confirming this will work. (?)
Click to expand...
You need some way to make sure writing data to the latches doesn't mess
up your SDA & SCL lines.
 
On 2020-04-11 10:22, mpm wrote:
Pretty sure the answer is "Yes", but let me ask it anyway....

Situation:
Need to add a datalogger to an existing design, but there are no free ports left on the microcontroller.

The microcontroller is an AT89LP51ED2. (An 8-bit, 8051 variant)
Port-0 outputs data ONLY to (3) D-Type transparent octal latches (74ACT573N), which are individually latched via some pins on Port-2 of the microcontroller.

The latches are written infrequently, and are never left un-latched in normal operation (i.e., we don't use the "transparent" feature of this part).

So....

Can I use a couple of Port-0 port pins for I2C SDA & SCL lines to connect up some parts to make a datalogger? (I'm thinking a 24C32 for the memory, and DS3231 for the RTC.)

It seems to me that as long as the 573 latches are latched with the intended data, I can then do whatever I want with the Port-0 pins (such as service a RTC & Memory datalogger).

All the voltages are OK (+5 VDC is used everywhere in this particular product).

So other than adjusting the code, is there anything I'm missing?

Thanks for looking / confirming this will work. (?)
Click to expand...

Another approach would be to replace the 573 with a 595, which would
free up 5 pins.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
On 2020-04-11 11:52, Lasse Langwadt Christensen wrote:
lørdag den 11. april 2020 kl. 17.39.31 UTC+2 skrev Phil Hobbs:
On 2020-04-11 10:22, mpm wrote:
Pretty sure the answer is "Yes", but let me ask it anyway....

Situation: Need to add a datalogger to an existing design, but
there are no free ports left on the microcontroller.

The microcontroller is an AT89LP51ED2. (An 8-bit, 8051 variant)
Port-0 outputs data ONLY to (3) D-Type transparent octal latches
(74ACT573N), which are individually latched via some pins on
Port-2 of the microcontroller.

The latches are written infrequently, and are never left
un-latched in normal operation (i.e., we don't use the
"transparent" feature of this part).

So....

Can I use a couple of Port-0 port pins for I2C SDA & SCL lines to
connect up some parts to make a datalogger? (I'm thinking a
24C32 for the memory, and DS3231 for the RTC.)

It seems to me that as long as the 573 latches are latched with
the intended data, I can then do whatever I want with the Port-0
pins (such as service a RTC & Memory datalogger).

All the voltages are OK (+5 VDC is used everywhere in this
particular product).

So other than adjusting the code, is there anything I'm missing?

Thanks for looking / confirming this will work. (?)


Another approach would be to replace the 573 with a 595, which
would free up 5 pins.


it would free even more, only three pins needed to drive a string of
shift registers, instead of the 8data + 3latch
Click to expand...

Five pins, for large values of five. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
lørdag den 11. april 2020 kl. 17.39.31 UTC+2 skrev Phil Hobbs:
On 2020-04-11 10:22, mpm wrote:
Pretty sure the answer is "Yes", but let me ask it anyway....

Situation:
Need to add a datalogger to an existing design, but there are no free ports left on the microcontroller.

The microcontroller is an AT89LP51ED2. (An 8-bit, 8051 variant)
Port-0 outputs data ONLY to (3) D-Type transparent octal latches (74ACT573N), which are individually latched via some pins on Port-2 of the microcontroller.

The latches are written infrequently, and are never left un-latched in normal operation (i.e., we don't use the "transparent" feature of this part).

So....

Can I use a couple of Port-0 port pins for I2C SDA & SCL lines to connect up some parts to make a datalogger? (I'm thinking a 24C32 for the memory, and DS3231 for the RTC.)

It seems to me that as long as the 573 latches are latched with the intended data, I can then do whatever I want with the Port-0 pins (such as service a RTC & Memory datalogger).

All the voltages are OK (+5 VDC is used everywhere in this particular product).

So other than adjusting the code, is there anything I'm missing?

Thanks for looking / confirming this will work. (?)


Another approach would be to replace the 573 with a 595, which would
free up 5 pins.
Click to expand...

it would free even more, only three pins needed to drive a string of shift registers, instead of the 8data + 3latch
 
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