JustEnoughDucks

Hello,

I am making an open source privacy-first fitness band for myself and I am writing the firmware now as someone relatively inexperienced at firmware development (I am an electronics engineer by trade). I get it done but sometimes I run into concept issues, especially when I start overthinking, like now that I need help with.

I have a macronix SPI NOR flash on-board that I want to use as offline activity saving, backup at low battery, etc... I am dreaming up the data structure for it. Here is the values I need to save to not lose information and what will be required for my supported features in the Bluetooth Physical Activity Monitor Service:

struct memory_map_nor {
    time_t timestamp;
    uint16_t sub_sess_id;
    uint32_t steps: 24;
    uint8_t bpm;
    float16_t spo2;
    uint16_t pulse_inter_beat_interval;
    uint16_t cadence;
    uint16_t speed;
    uint16_t activity_level;
    uint16_t activity_type;
    uint16_t temp;
};

So from this datastructure, it has a total of 28 bytes of data. This has to fit on a 256 byte page, which means 9 "rows" of data can be written per page, 144 per sector, 2304 per 64 bit block, and 147456 in total for a 32Mbit NOR.

But, I am getting confused while reading about memory structures in "normal" processors that need to read everything in 4/8-byte words via the parallel interfaces. This means that conventionally, everything has to be padded to neat structures that are divisible by 4 (32-bit) for QSPI reading. In that case, I would either have to add another 32 bits of data or pad 32 bits to every "row", making a neat 8 data "rows" per page.

OR, because I am only using single lane SPI, would this not matter and I could shove an extra datapoint in each page. The difference is 147456 data rows vs 131072 data rows. At 3s polling rate, that is 5.12 days vs 4.55 days. For my application, the difference might be useless anyway, but the band goal battery life is 2 weeks or so.

Again, maybe I am overthinking this and can just pad the data to make everything neat and fit well. Anyone have any opinions? Thanks!

I have been getting beaten down between 24/7 job uncertainty with the bad engineering market right now, a full-strip house renovation, and not sleeping well.

Yesterday renovation with my girlfriend's family I hit a breakpoint of just going numb after the 3-4 hours of work I put into building the bath frame has to be shortened by 2cm to get the tiles flat that I wrongly calculated because my brain doesn't work anymore. Like 50% of the work has to be redone and half of the holes through the tiles carefully redrilled.

Today I actually took a day off just working on my personal electronics project. Just a nice, sunny day playing with our dog, doing a bit of gardening and actually enjoying the day instead of just going and going renovating or working or going to social events. I really needed it. Back to the grind tomorrow.

I played rimworld on and off casually for a few years. <100 hours in the game. I could never make it to the spaceship though I did have a pretty good colony or two.

Sorry here is the rant of my recent colony I tried playing for hours and hours:

I bought ideology and came back to rimworld because it sounded fun and wanted a simple tribal start. Everyone said arid shrublands is easy so sure. i picked pheobe on normal difficulty because I was looking for a relaxed time. Everyone says arid shrublands is the easiest.

Holy shit. 4 animals on the entire map + 1 herd of elephants. Almost no trees whatsoever, and researching is so damn slow that I have only had stonecutting and complex furniture done in 2 years. Electricity by itself would take 3-4 years of non-stop research...

Meanwhile, there is no way to heat or cool anything because campfires make a room boil (and there is no wood) and passive coolers don't work (and there is no wood). I have a giant cactus farm, but don't worry, somehow it takes 2 seasons to fully grow when it says 15 days on the card and it is 100% fert. So that doesn't help much. So there is no way to cool except to go into the mountains. Fine, except oh wait, when it is 60C outside, it is still 50C in the heart of the mountain when everything has doors...

I have half the map covered in agriculture and the heat is so intense (35-60C and never ever ever drops below that) means that I have to use every bit of spare wood for cooking and every single day is a fight to have enough food. I have to rotate out cooks because they will pass out in the kitchen.

Then I am hit with heatwave after >70C heatwave. Crippling and incapacitating all of my colonists for a week at a time until everyone is starving. Don't even think of cooking during a heatwave. Then it will get to over 80 in the room to cook one meal and the colonist will instantly go down. Not to mention the frequent heat storms during the heatwave to set everything on fire, but of course there I'd no technology like "a bucket of water" so my colonists have to let it all burn or die of heatstroke trying to pat it out lovingly with their bare hands.

2 raiders in 3 years, 0 chance to supplement my 5 colonists in any way at all. Each of those 2 raids had the people instantly killed, so no chance to recruit.

I can't hunt because my tech is so bad and my colonists are so slow that shooting an elephant once means they charge across the map and wipe out all 5 colonists in 30s

I can't raid because every single day is a fight for food for the day and the colonist tech is so bad they would get destroyed instantly.

I can't research armor because that would take years and years and I need to sink every minute in every day trying to get electricity so the next heatwave doesn't wipe me out.

Pretty much I am stuck in the most difficult fight for my colony every minute of every day and it simply isn't fun at all. Not eventful at all either. There is no story, just a slow grind of no technology and brutal, never ending heatwave conditions. This is what I assumed desert would be like, not arid shrublands...

That isn't even mentioning the weekly "mad hare"... some world that this is, 1 mad rabbit will beat 2 people, 1 with a spear and one with a revolver. What on earth. Then I am down to 3 people for at least 3 days while they recover. No way they will go down my completely open spike corridors either, they will just wait outside until I need someone to harvest agave outside of the walls where 1 single scratch takes your colonist down to 20% movement speed and it can just run them down...

/rant

Sorry, I hear people say that arid shrublands are the easiest biome, but holy hell would I disagree. If your farm isn't churning out rice within the first few days, you are simply completely dead.

In Belgium, we are forced by law to use Cca data cables because of "lower fire risk" while I hear literally everywhere that CCA data cables have a much higher fire risk.

Everything here has to comply with the euroclass chart level cca or higher which is confusing because they seem to be combustibility(ca) ABCDEF rating. Making the minimum required in Belgium (and the most prevalent) Cca.

I think for example that getting this for PoE (sorry, in Dutch) would be fine because it does say that it is pure copper, but it also says that it is CCA which is confusing.

Not really a question or anything, just very confusing considering Cca and Eca are the 2 cable types used for residential homes which happen to correspond also to Copper clad aluminum and Enhanced Circuit Integrity. Adds extra probably completely unnecessary stress.