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UART in Mimas v1 Spartan-6 FPGA Board

Discussion in 'FPGA Boards' started by Jay Mangaonkar, Dec 29, 2015.

  1. Jay Mangaonkar

    Jay Mangaonkar New Member

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    I recently purchased a Mimas FPGA board and it is amazing.
    But, I wanted to know how to perform UART serial communication using this board.
    I found an example on UART for Mimas v2 board here (https://github.com/cyrozap/Mimas-V2-UART-Demo) but cannot figure out how to use it in the context of v1 board.
    The datasheet for Mimas v1 doesn't mention about this where as it is mentioned in Mimas v2.
    Since both the boards have same FPGA and PIC controller, I hope UART can also be done from Mimas v1 board.
    Can someone help me in this regard.


    Thanks,
    Jay Mangaonkar.
     
  2. Regelink

    Regelink New Member

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    I am looking into this too. Section 2.8 of the Mimas v2 user manual specifically describes the possibility of UART communication between an FPGA implementation and a PC application over the USB link. It looks like https://github.com/cyrozap/Mimas-V2-UART-Demo is configured to use that (since RX and TX are mapped to A8 and B8 respectively in the user constraint file, which are mentioned in section 2.8 of the Mimas v2 user manual). One can always use other digital pins to do UART communication, but that would require one to connect a USB to serial (TTL) converter cable to those pins on the Mimas header.

    It would be nice if someone can elaborate on whether the USB-UART feature available in the Mimas v2 board is also available on the Mimas v1. I think it is a matter of PIC firmware.
     
  3. rohith

    rohith Moderator Staff Member

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    Hello Jay,

    While MimasV1 does have a PIC as in MimasV2, its firmware doesn't have feature for USB-UART bridge and also, there is no connection from PIC to FPGA for UART interfacing. You would need an external USB-Serial Module for UART interfacing on MimasV1.

    Regards,
    Rohit
     
  4. srmeister2

    srmeister2 New Member

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    Hello,
    has Mimas V1 got an update? Because i can see a connection between PIC Pins 5-8 (Bus D[0...3]) to the FPGA. Is it maybe possible to connect from FPGA to PIC to PC ?
    I am interested if its possible to use UART from FPGA to PC?
     
  5. analog_digital

    analog_digital New Member

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    To give you an "hacking reply": IN THEROY something could be possible. But it will take really long time.

    In Mimas v2, as u can see in the schematic, Tx and Rx Pins of pic are hardwired to Fgpa GPIO, in mimas v1 they are not. The D[3..0] bus you are referencing, are GPIOs for Pic, so one should implement a Soft Uart (or even soft I2c or soft SPI) in PIC Firmware.

    So if u want proceed in this way, you should write a new pic firmware for mimas v1 board from zero (AFAIK doesn't exists an open firmware for Mimas v1, unlike the Mimas v2). But numato didn't provided original mimas v1 firmware to bring the board back to original state so you will risk to transform your mimas v1 in a fantastic bricked decorative object for your desk....
     
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  6. rohith

    rohith Moderator Staff Member

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    @srmeister2 In addition to the excellent reply by @analog_digital, allow me to mention that MimasV1 always had those connections to FPGA. It was only that its firmware didn't support UART bridge capability.

    As @analog_digital said, it is possible theoretically and even practically, but you would need to implement the soft-uart firmware and we are not sure the best baudrate which you can get out of that.

    The programming protocol for MimasV1 can be found from the MimasV1 programming script in our Github repo. You are welcome to hack things around!
     
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  7. srmeister2

    srmeister2 New Member

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    OK Thank you guys i understand what you are saying, unfortunately im not a PIC expert. But i remembered that i have a 3.3V FT232 to USB cable laying around and i will use this now.
     
  8. srmeister2

    srmeister2 New Member

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    omg i cant believe this.
    In schematics, on header P1, Pin1 is GND and Pin2 VCC but on the manual it says its the other way around.
    Nice work you did there, i almost fried the on board voltage regulators by believing the schematics
     

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