Manipulating registers in STM, and data transfer idea

[Wells]

Hi,

Now that I'm up and running on my Blackice 2, I'd like to start using the STM's peripherals; I'm thinking about writing a PID controller into the FPGA and using the ADC and DAC on the STM to interface with whatever system I want to control.

First, I've done register access in Arduino to the micro that the UNO uses so I'm somewhat familiar with how that works, and I have the STM data sheet handy so I know where to find the relevant register names, as well as how to look for procedure requirements/restrictions etc.

My first question: is the process similar for the STM? My goals include setting up the ADC and DAC with specific bit-widths and finding settings that give fast conversions, among others.

------ Edit: I'm probably not going to pursue the approach below after looking into it, my apologies for writing down a brainstorm too soon after having it. Maybe it'll start some discussion anyway...------

Second question: I had assumed I would transfer data between the STM and FPGA using QSPI, which I have done in the past. However it occurred to me that it might be faster if I could port the ADC_DR register (ADC data reg.) and the relevant DAC input register to shared pins and R/W them directly from the FPGA, kind of like a parallel interface custom to my application. If I am working with 8 bit data it would use 16 pins for both directions and seems to me it would be nearly immediate.

(disclaimer: while I'm not a noob I'm also lacking any formal training in computer science, and as such my areas of knowledge tend to be fragmented, so if I'm WAY off because of something obvious to a more well-rounded person, that's why :))

Thoughts?

Thanks, Wells

[lawrie]

Are you planning to program the STM32 using Arduino or the STM HAL interface? Arduino is simpler, but I don't know what support there is for the DAC in myStorm Arduino.

I don't believe there are enough pins between the STM32 and the ice40 FPGA, for you to transfer data in parallel, so QSPI is probably your best bet.

[Wells]

Hi lawrie,

Arduino. I've done a bunch of register access stuff on the Uno's chip, and a little on the Zero, though I can't remember what that chip is offhand. I think I went well outside the Arduino language and may have been using a different uploader at some point, but it's been a while. As I'm working in OSX, programming my Blackice 2 board is done through the Arduino IDE, with a bitstream incl. in the Arduino "sketch". Most of my projects have at least an empty .ino file in a dir. of the same name, along with a folder called FPGA for the verilog, etc.

I'm ok implementing peripherals or changing their registers that aren't written into the Arduino or it's libraries, but haven't done it on this chip yet. I'm aware as well that this can involve going into some of the Arduino's resources and making changes, and am doing so at my own risk. I also know how to reload all the firmware to all the chips on the board, so if (when) I totally brick it up solid (again) I can just start over

I just finished editing/putting a note on my post saying I've moved on from the parallel idea, and yes after looking into it (which I should have done before hiccuping my thoughts of the moment onto my registers post) it would use almost all the digital pins. For some reason I thought there were more, but maybe I'm thinking of the Zero...

Anyway I'm starting to monkey with the registers shortly, starting with the ADC then the DAC. Will post anything interesting,

Wells