GPIO from the management core works fine for me but output f

Question

GPIO from the management core works fine for me but output from the user space doesn t seem to I basically have a scan chain 112 bits long with the scan in clk enable coming from GPIO and the output going to GPIO and I can t get anything to scan through it I ll have to check the reliability of the GIO configuration maybe

Matthew Guthaus · Answer

Is there a way to adjust the LDO from C firmware

gatecat · Answer

How fast are you running the IO Inputs are fine at any speed but with the default setup outputs will be in a weak pull down iirc mode that are fast to rise but slow to fall

gatecat · Answer

This can be changed given certain constraints <https open source silicon slack com archives C03UVJCTR8U p1675881326429439 thread ts=1675780488 497159 amp cid=C03UVJCTR8U|https open source silicon slack com archives C03UVJCTR8U p1675881326429439 thread ts=1675780488 497159 amp cid=C03UVJCTR8U>

gatecat · Answer

in general it s easiest to get fast outputs if they re surrounded by inputs

Tim Edwards · Answer

< Matthew Guthaus> If you re looking to set the voltage it needs to be done through the Nucleo by passing a voltage to the `powerup sequence ` routine For the configuration please post some code and I can check it to see if the configuration is valid As < gatecat> mentions if you are trying to run more than about 1MHz then the default output type which has a slow fall time may fail to reach a low logic value Otherwise it s probably a configuration issue

Matthew Guthaus · Answer

< gatecat> 100Hz

Matthew Guthaus · Answer

Can I run micropython to change these settings and then run my firware I thought I need the micropython firmware to do these things Maybe I m conceptually missing something

gatecat · Answer

The pin configuration itself is ultimately done by the C code running on the caravel The micropython code is responsible for programming that into the flash and in combination with the caravel working out what the hold failures in the IO chain are by testing various IO configurations

Matthew Guthaus · Answer

I m also not using the default pin setup I have my own setup

Matthew Guthaus · Answer

It s using the gpio config def py with my custom timing

Matthew Guthaus · Answer

The micropython is running on the nucleo board and not the caravel chip

Tim Edwards · Answer

Yes the micropython is running on Nucleo not caravel

jeffdi · Answer

< Matthew Guthaus> can we get on a call to quickly over what you are trying to do

Matthew Guthaus · Answer

< jeffdi> Yes

Matthew Guthaus · Answer

Ok but when I flash nucleo that overwrites the micropython firmware correct

jeffdi · Answer

Tim Edwards · Answer

< Matthew Guthaus> Check the post from yesterday from < Yatharth Agarwal> with the flowchart of how the system works It s a very nice illustration

Tim Edwards · Answer

< jeffdi> There are definitely some problematic issues with `gpio config builder py` for user configuration The key is to maximize the shortest run of zeros in the entire configuration You will only be able to get a run of zeros of length N past N 1 dependent hold violations Any more than that the number of extra 1s that have to be added collides with the neighboring configuration word The current definition for C USER bit configurations includes things like `0110000000010` for C USER OUT Put two of those in neighboring channels and your shortest run of zeros is two meaning that you can get that configuration only through one dependent hold violation before it stops working Fortunately since the user side interface is a three pin bidirectional inteface most of the configuration word doesn t even affect how the user project generates or accesses data The only exceptions are the management enable bit must be `0` for any user mode and the 3 bit output mode I would advise that `C USER IN NP` be set to `0010000000000` and `C USER OUT` be set to `0110000000000` User weak pull up and weak pull down input modes can be left as is but require that the user has understood that these modes require driving the output which they will need to have done appropriately in their design The abovementioned definitions will survive through a series of nine dependent hold violations The output mode will have a weak pull down and users who need a gt 1MHz output should get in touch with us on how to arrange the configuration to make that happen