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Problem with ISP on micro:bit

balearicdynamics

I have a strange issue with the micro:bit that I have no idea by what it can depends. Maybe also a behavioural detail I have not considered and I am expecting something that it is normal does not happens.

 

The scenario

For more detail on how the project is designed take a look to the blog posts on Tempus fugit...

 

Tempus Fugit... Part 1: 1978 a.d.  project intro

Tempus Fugit... Part 2: 2018 a.d. the components and the logic of the project

Tempus Fugit... Part 3: micro:bit Interfacing 5V Logic the first issue: interfacing 3.3 logic signals from micro:bit to 5V logic on IC. Tested and solved

Tempus Fugit... Part 4: micro:bit 5V SPI adopting the solution discussed in the previous blog post to my use case: 7-segments LED controller via SPI protocol.

 

The problem

Hardware seems working properly; with simple programs to control the pins involved by the SPI protocol (13, 14, 15 on the micro:bit) and testing with the oscilloscope bon both sides 3.3 V (output connector from the micro:bit) and 5V (input connection to the IC) these works perfectly and there are no problems. Then, I tried to implement in Python using MU the SPI protocol and on the same pins controlling with the oscilloscope nothing happens. To do this I have used the Python library to control the specific IC but none at all. I am not interested in this moment to see the display working. What I just need to understand is what can be the issue that is blocking the SPI protocol to work correctly, also when the test program runs on on the micro:bit without the controlled circuit connected to avoid interferences. The same behaviour happens on a second micro:bit board, while the digital output setting of the pins with the test program continue working; I can suppose that there is not any hardware problem.

 

Any suggestion and idea is more than welcome image

 

Enrico

Parents

  • This code works with the Python Editor on their website

     

    # Add your Python code here. E.g.
from microbit import *

buf = bytearray(1)

spi.init()

while True:
    buf[0]=0xa4
    spi.write(buf)
    sleep(20)

     

    these are the output signals (yellow=clock,blue=data)

    image

     

     

    That's with the default init settings.

     

    But that's with the SPI in the microbit module. I don't know if working with MU is the same or whether you'd need to do something different.

Reply

  • This code works with the Python Editor on their website

     

    # Add your Python code here. E.g.
from microbit import *

buf = bytearray(1)

spi.init()

while True:
    buf[0]=0xa4
    spi.write(buf)
    sleep(20)

     

    these are the output signals (yellow=clock,blue=data)

    image

     

     

    That's with the default init settings.

     

    But that's with the SPI in the microbit module. I don't know if working with MU is the same or whether you'd need to do something different.

Children
  • in reply to jc2048

    Hi John,

     

    thank you for the experiment. I have done the same and got always the same result I got with MU. This is just an editor specific for micro:bit working on local files but includes all the libraries. Anyway, with the standard editor of microbit.org with your code, downloaded and sent to the board nothing happens. In both cases, using the micro:bit with the controller connected and with a different micro:bit board without any circuit. image

     

    As the pin themselves works fine when I use write_digital(), I suppose that there is something or some setting I am not making correctly but I have no idea what can it be done.

     

    Enrico