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TMS320F28386D-Q1: Controlling LCD at 1 meter distance

Danilo A.
Mastermind 26450 points
Part Number: TMS320F28386D-Q1

Hi Team,

Can you please help us with our customer's inquiry below?

I would like to manage an LCD display (128 x 64 Pixels module) and to contain the costs of my application I would like to choose one with parallel communication. The LCD screen should be about one meter from the PCB that controls it and I would like to ask you, since I do not find documentation on ti.com, if there are techniques to manage parallel communication protecting it from any disturbances.

The device I would like to use is the tms320f28386d-q1. I know that it has tms320f28386d-q1 CM-I2C as its peripheral, I would change my mind about the choice of the LCD screen if I find any schematics on ti.com that implement the CM-I2C peripheral. I did not understand if it is the same as a simple I2C peripheral and if it is possible, with a transmitter (eg RS485 ..), to keep the LCD screen at one meter of the tms320f28386d-q1 board.

Regards,

Danilo

  • 0
    TI__Mastermind 27021 points
    Danilo A. said:
    I know that it has tms320f28386d-q1 CM-I2C as its peripheral, I would change my mind about the choice of the LCD screen if I find any schematics on ti.com that implement the CM-I2C peripheral. I did not understand if it is the same as a simple I2C peripheral

    There are actually 3x I2C peripherals on the F28386D device. One is the CM-I2C and the other two are C28x I2Cs. The CM-I2C register interface does differ from the C28x version, but the I2C electrical/protocol functionality itself is the same. 

    Regarding your main question of driving an LCD from 1m, have you considered using a simple buffer IC? 

    https://www.ti.com/logic-voltage-translation/overview.html

  • 0 in reply to Gus Martinez
    TI__Mastermind 26450 points

    Hi Gus,

    Thank you for your response. Please see the feedback of our customer blow.

    so for what i understand i should use config:
    microcontroller >> digital isolator >> buffer >> 1 or 2 meters of cable >> expander port >> LCD
    Is a buffer sufficient in this configuration, even in a noisy environment full of synchronous / asynchronous motors? the I2C so extended is not severely affected? Would digital isolators help prevent ground loops (always taking the capacitance of them into account) or would they be better than TVS diodes (maybe they have lower capacitance, I have to check) and use various ground paths in PCB layers?
    that 1 or two meters of cable must be twisted pair? must the SDA and SCL signals be on two different pairs or must they intertwine on the same pair? or do I have to use non-twisted pairs?

    I know I am obsessed with the CM-I2C, but I don't understand, if the registers are different from a simple I2C peripheral, are they also physically different? given that in the technical sheet it is stated that the CM-I2C is used to manage serial memory (RAMs and ROMs),networking devices, LCDs, tone generators ... while I have always read around that I2C is used purely on the PCB, and to extend it you have to count exactly the total capacity of the network (I have read many documents on ti.com about it)
    Also, using a protocol that uses addressing is useful to me as it makes the network extensible for future uses, unlike what you can do with a UART protocol (CM-UART, this too I don't understand what it does different) or SCI together with an RS485 or RS422 differential bus in a configuration such as:
    microcontroller >> digital isolator >> RS485 / RS422 transceiver >> 1 or 2 meters of twisted pair >> expander port >> LCD

    Regards,

    Danilo

  • +1 in reply to Danilo A.
    TI__Mastermind 27021 points

    Danilo,

    Danilo A. said:
    so for what i understand i should use config:
    microcontroller >> digital isolator >> buffer >> 1 or 2 meters of cable >> expander port >> LCD
    Is a buffer sufficient in this configuration, even in a noisy environment full of synchronous / asynchronous motors? the I2C so extended is not severely affected? Would digital isolators help prevent ground loops (always taking the capacitance of them into account) or would they be better than TVS diodes (maybe they have lower capacitance, I have to check) and use various ground paths in PCB layers?
    that 1 or two meters of cable must be twisted pair? must the SDA and SCL signals be on two different pairs or must they intertwine on the same pair? or do I have to use non-twisted pairs?

    I suggest you post to the Interface forum to get some better recommendations for your customer. 

    Danilo A. said:
    I know I am obsessed with the CM-I2C, but I don't understand, if the registers are different from a simple I2C peripheral, are they also physically different? given that in the technical sheet it is stated that the CM-I2C is used to manage serial memory (RAMs and ROMs),networking devices, LCDs, tone generators ... while I have always read around that I2C is used purely on the PCB, and to extend it you have to count exactly the total capacity of the network (I have read many documents on ti.com about it)

    The CM-I2C and C28x-I2C are different peripheral designs that support the same I2C standard. All feature and electrical specs for the CM-I2C and C28x-I2C are given in the datasheet. The customer can refer to these specs to deep dive in to the differences between the two modules if needed. One important difference is that the CM-I2C is only accessible from the ARM Cortex-M4 & uDMA on the device and the C28x-I2C is accessible only from the C28x core on the device, see Figure 3-1. Functional Block Diagram in the datasheet. 

    Danilo A. said:
    Also, using a protocol that uses addressing is useful to me as it makes the network extensible for future uses, unlike what you can do with a UART protocol (CM-UART, this too I don't understand what it does different) or SCI together with an RS485 or RS422 differential bus in a configuration such as:
    microcontroller >> digital isolator >> RS485 / RS422 transceiver >> 1 or 2 meters of twisted pair >> expander port >> LCD

    The CM-UART is another peripheral designed to work with the ARM Cortex-M4. The feature and electrical specs for the CM-UART are given in the device datasheet. The CM peripherals are only accessible from the ARM Cortex-M4 & uDMA.