nichx
Posts: 2
Joined: Sun Jun 28, 2020 6:41 am

[Troubleshooting] - Sense Hat LED Matrix only lights in column

Sun Jun 28, 2020 6:53 am

There are a few variables in the mix here; I have an RPi Zero W I self-soldered headers to. I installed the Sense Hat on those headers. After going through the motions of adding 'dtoverlay=rpi-sense' to /boot/config.txt and a few other massaging steps, it's mostly working. However, the LED matrix only seems to display in columns at the moment. Addressing a couple pixel to be red and blue, like this this example:

Code: Select all

from sense_hat import SenseHat
sense = SenseHat()

blue = (0, 0, 255)
red = (255, 0, 0)

sense.set_pixel(0, 2, blue)
sense.set_pixel(7, 4, red)
the entire left column is red, and the entire right column is blue. I tried to fiash the EEPROM on the hat, but get:

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Writing...
dd: failed to open '/sys/class/i2c-adapter/i2c-0/0-0050/eeprom': Permission denied
Closing EEPROM Device.
Error doing I/O operation.
despite disabling write protection with:

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i2cset -y -f 1 0x46 0xf3 1
as suggested here https://www.raspberrypi.org/documentati ... sense-hat/.

Any help is greatly appreciated!

nichx
Posts: 2
Joined: Sun Jun 28, 2020 6:41 am

Re: [Troubleshooting] - Sense Hat LED Matrix only lights in column

Mon Jun 29, 2020 4:08 pm

FYI:
It would appear to have been a bad hat or EEPROM. A new hat works as expected.

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bensimmo
Posts: 4550
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: [Troubleshooting] - Sense Hat LED Matrix only lights in column

Mon Jun 29, 2020 4:37 pm

Bad luck I guess. Never seen one do that.
I've never seen anyone actually try to flash the AVR either.

I would have thought with the LED, matrix, unless the on board connection or LEDs are faulty, then it's either all works or noting work with the LED. (I had one led fail after a while)

trejan
Posts: 1834
Joined: Tue Jul 02, 2019 2:28 pm

Re: [Troubleshooting] - Sense Hat LED Matrix only lights in column

Mon Jun 29, 2020 4:47 pm

bensimmo wrote:
Mon Jun 29, 2020 4:37 pm
I've never seen anyone actually try to flash the AVR either.
They're rewriting the HAT EEPROM.

The source and the avrdude incantation is on the rpi-sense repo if anybody does want to reflash the AVR though. The documentation only has a blank section for reflashing the AVR for some reason.

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bensimmo
Posts: 4550
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: [Troubleshooting] - Sense Hat LED Matrix only lights in column

Mon Jun 29, 2020 5:02 pm

Ah, but the EEPROM only does the ID part to enable the right overlay? Which has been manually enabled.

Must laugh at myself, although it says EEPROM in the post, I assumed they meant the AVR for the above reason.
So still not out any AVR modding instructions up.


Anybody had a play yet?

alphanumeric
Posts: 2513
Joined: Tue Jan 19, 2016 2:17 pm
Location: Sydney, Nova Scotia, Canada

Re: [Troubleshooting] - Sense Hat LED Matrix only lights in column

Tue Jun 30, 2020 1:04 pm

The pinout is here, https://pinout.xyz/pinout/sense_hat
From the looks of it everything is done via i2c. I would if you can, plug that sense hat into a Pi that came with a pre soldered header.
Maybe one of the ground pins needed by the sense hat isn't making a good connection? They are all one common ground on the Pi but may not be all wired to one common connection on the Hat itself? Having one or more IC's missing their ground connection would I think cause some weird things to happen and or not work at all.

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