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Experimenting with Gesture Sensors
Forum Establishing serial communication over UART instead of USB in MAX25405 EVKIT
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  • MAX25405
  • gesture sensors
  • maxim integrated
  • uart
  • max32620fthr
Related

Establishing serial communication over UART instead of USB in MAX25405 EVKIT

rsjawale24
rsjawale24 over 2 years ago

The MAX25405EVKIT comes with a MAX32620FTHR board which is preprogrammed with custom binary file for the gesture recognition. The application note at Maxim Gesture Sensor EVKit Serial API (maximintegrated.com)

mentions "The serial interface can be implemented over the Universal Serial Bus (USB) virtual serial port or over a Universal Asynchronous Receiver-Transmitter (UART). The EV kit is shipped configured to use the USB serial port to work with the EV kit PC Graphical user Interface (GUI). If a UART serial interface is desired, custom firmware in binary format is available."

Upon researching more, I found the firmware_framework code that contains the code for gesture recognition compiled using mbed compiler.

The readme file says that a file called interface.h and interface.c define the communication protocol. When I open the interface.c file, I can see a comment in the code that says Option to implement serial API over UART instead of USB but there is only a MACRO set as #define macro_name 0 

I tried to change the 0 to 1 and compile the code, however, it does not compile successfully. The USBDevice library shows some error while compiling. 

Did anyone try to change the serial API over UART instead of USB? Was it successful?  

EDIT: I have successfully compiled the code for UART. However, I'll do some experiments and write introductory blogs before I re-program the MAX32620FTHR board with my firmware. 

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Top Replies

  • misaz
    misaz over 2 years ago in reply to misaz +4
    Today I found root cause of the issue. Issue is caused by invalid assembly code generated by modern ARM compiler. With older GCC compiler it works because it handle undefined behaviour used in code differently…
  • misaz
    misaz over 2 years ago +3
    I am curious how did you successfully compiled non-changed code? I started working with latest mbed-os but I was unable to compile it (missing toolchain) no matter of USE_UART_INTERFACE setting. Later…
  • BigG
    BigG over 2 years ago in reply to rsjawale24 +3
    I've create a very basic stripped down library based on the firmware framework using the latest MbedOS 6.16. github.com/.../Max25x05_MbedOS6 All it is doing is getting the raw pixel data. It is doing…
  • misaz
    misaz over 2 years ago in reply to BigG

    He want to do something different. By default firmware communicates with computer over virtual UART over USB. But he do not want this virtual UART. Rather he want real UART. He do not want to comunicate with board from computer but he want use Arduino instead. He correctly found macro which can switch firmware to use real instead of virtual UART but his communication do not work. I am currently out of home so I cant try his firmware but I will do this this weekend.

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  • misaz
    misaz over 2 years ago in reply to rsjawale24

    Do you use any level shifter? What is your connection? Can you post some photo?

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  • rsjawale24
    rsjawale24 over 2 years ago in reply to BigG

    I'm using the same version as misaz has used in his mbed CLI. 
    I'm using the git commitID 0fdfcf7350896a9c0b57c4a18237677abfe25f1a 

    I'm not sure which version it belongs to. But it is the only one that gives no error in compiling the firmware framework provided by Maxim.

    My aim is to get the gesture results over UART so that it can be sent to any general MCU like Arduino. 
    With the above-mentioned release of mbed, the code works fine for USB so it should work for UART as well as the basic structure of code remains same, only the path where data is sent changes from USB to UART.

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  • rsjawale24
    rsjawale24 over 2 years ago in reply to misaz

    Hi! No, I'm not using any level shifter, I assumed that UART is using the standard logic levels. 

    Here's my connection diagram -

    image

    Baud rate for both the devices is 115200. 

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  • misaz
    misaz over 2 years ago in reply to rsjawale24

    Do you have voltmeter (multimeter)? If yes, try disconnect wires and measure voltage on MAX32620 TX pin. It would be one of 1.8V or 3.3V. What Arduino do you use? ATMega based or some newer ARM Arduino? In case of standard 5V Arduino UNO this connection is dangerous. In case of newer ARM based Arduinos which are usualy powered by 3.3V this connection may be sufficient in case if you measure 3.3V on TX pin.

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  • rsjawale24
    rsjawale24 over 2 years ago in reply to misaz

    Ah! I tried multiple arduinos. Uno, Micro and then MKR WAN 1300. Let me do the measurements on the pins. I had completely forgotten that MAX32620 has different voltages then the standard MCUs. I'm reading about 0.8V on the Tx pin of the MAX32620. I'll check the datasheet for the UART logic levels. 

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  • misaz
    misaz over 2 years ago in reply to rsjawale24

    0.8V means pin in High Impedance so this pin is not the output (which TX should be). 0.8V (or any other different than 0V, 1.8V and 3.3V) you should measure on RX pin. On what pin do you measure voltage?

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  • rsjawale24
    rsjawale24 over 2 years ago in reply to misaz

    I measured on Tx 0V and Rx 0.8V

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  • misaz
    misaz over 2 years ago in reply to rsjawale24

    Interesting. RX is OK but TX should be in logical 1 when indle but your pin is in logical 0 state for some reason. Does the 0V remains after reset?

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  • rsjawale24
    rsjawale24 over 2 years ago in reply to misaz

    Yes Tx remains 0V after reset as well. I'll try some example firmware for UART to check if it works. 

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