STAR Firmware by JonnyC - Source Code and Explanation

A couple of members have recently sought a “1 mode” driver/firmware for various reasons.

Using STAR as a base, it’s easy enough for people with limited code skills such as myself to comment out all modes bar 255, but I found that this method doesn’t play nice with the low voltage warning/step down, as there is no lower mode to step down to.

If I keep a 2nd lower mode in there, the code works as it should, but there will be instances where the lower mode can be inadvertently changed to, even when set to come on in High mode every time.

I want to keep the low voltage step down routine, so “Mr. Muggles” sees the light has dimmed noticeably, & figures that it’s time to change the battery.

I’m thinking that the best solution would be to disable the part of the code that looks for the ‘quick-click’ for the mode change, or just shorten that time so as it’s not possible to click into the lower mode.

Could one of the code Guru’s help me out with what needs to be changed - I’ve tried to follow it through, but can’t put my finger on it.

Cheers :slight_smile:

I guess easiest would be to simply comment out the “next_mode()” call from the mode_idx&0x10 check (or comment out the entire mode_idx&0x10 check routine), disable mode memory and have mode direction high to low.

I assume we are talking about the clicky firmwares.

For the clicky firmwares I think the most straightforward way to handle it is to set the minimum stepdown brightness manually. This line determines the lowest PWM level the driver will stepdown to:

if ((PWM_LVL >> 1) < modes[0]) {

Note that it’s based on modes [0], the first mode, but in a single mode driver that’s the only mode we have! Instead we just set it like this:

if ((PWM_LVL >> 1) < 30) {

where “30” is the lowest level we want it to step down to in this case. Assuming the single-mode was set to 255, stepdown pattern would look like this:
255, 128, 64, 32, 30, 30, 30, etc, …, critical shutdown

If you’re building a lot of single mode drivers and plan to change the minimum stepdown level a lot you may use a define for that value, just add one at the top like:

#define STEPDOWN_MINIMUM 30

if ((PWM_LVL >> 1) < STEPDOWN_MINIMUM) {


EDIT: My kingdom for a [code] tag. The forum software is messing up the first code quote, the mistake is fairly visible though (modes with a superscript zero).

That's what I usually do: define a lower mode, but don't put it in the normal mode orders, then tell the program to step down to that level as the minimum. I also do the same thing when I want the turbo timer to step down to a "hidden" level.

Hi all,

I have a somewhat related question. Is there any way to use a pot to control a 7135 based driver?

See my posts a few pages ago where I started working on the code to do that with LVP integrated.

Alternatively you can use a VaraPower driver and hook up the PWM input on the 7135’s to the gate pin on the FET of the VaraPower (but do not route LED power through the VaraPower of course!).

Thanks for the help everyone, I’ll try defining the step-down level & adding it in there.

I’ll be flashing a couple this weekend if all goes well.

It should work to simply make the step-down reduce the PWM level without changing the mode index. Like, if the PWM_LVL is less than some minimum (10, maybe?) blink and shut off. Otherwise, tell it to cut the PWM level in half — “PWM_LVL = PWM_LVL >> 1;”.

If there’s only one level defined, any quick tap should return the light to its maximum level… and then it’ll step down when the voltage has been low for a while.

I’m assuming this is a clicky switch.

I think the clicky firmwares already behave in exactly this way (only the momentary firmware actually steps down through the modes IIRC). The issue is that with normal operation the “some minimum” is the lowest defined mode rather than an arbitrary value. After swapping in an arbitrary minimum (10, whatever) the behavior is almost exactly as you described, except that after we reach the (10) or whatever the firmware will maintain a constant output level until it hits the ADC_CRIT value, then it shuts down.

OK, I've defined the stepdown value in this section of the code;

=========================================================================
* Settings to modify per driver
*/

#define VOLTAGE_MON // Comment out to disable
#define STEPDOWN_MINIMUM 50 // Hidden mode level for low voltage step down
// #define MODE_MOON 6 // Can comment out to remove mode, but should be set through soldering stars
// #define MODE_LOW 12 // Can comment out to remove mode
// #define MODE_MED 39 // Can comment out to remove mode
// #define MODE_HIGH_W_TURBO 110 // MODE_HIGH value when turbo is enabled
#define MODE_HIGH 255 // Can comment out to remove mode
// #define MODE_TURBO 255 // Can comment out to remove mode
// #define TURBO_TIMEOUT 240 // How many WTD ticks before before dropping down (.5 sec each)

#define WDT_TIMEOUT 2 // Number of WTD ticks before mode is saved (.5 sec each)

#define ADC_LOW 130 // When do we start ramping
#define ADC_CRIT 120 // When do we shut the light off

/*
* =========================================================================

And altered the code at the end where the stepdown routine is;

// Flash 3 times before lowering
hold_pwm = PWM_LVL;
i = 0;
while (i++<3) {
PWM_LVL = 0;
_delay_ms(250);
PWM_LVL = hold_pwm;
_delay_ms(500);
}
// Lower the mode by half, but don't go below lowest level
if ((PWM_LVL >> 1) < STEPDOWN_MINIMUM) {
PWM_LVL = modes[0];
mode_idx = 0;
} else {
PWM_LVL = (PWM_LVL >> 1);
}
// See if we should change the current mode level if we've gone under the current mode.
if (PWM_LVL < modes[mode_idx]) {
// Lower our recorded mode
mode_idx--;

I'm bench testing this with a partially charged cell, starting around 3.2v, & letting it run down.

I don't get the three flashes + stepdown to the defined value (50.)

Instead, it goes straight to the 10 flashes for critical voltage, but does not power off.

At no point does it step down to the predefined value (50).

What have I done wrong?

I was thinking about that also a few weeks ago, It should be fairly easy to make a voltage divider with the pot, and put it to ADC.

In order to maintain use of the full physical throw of the pot and have the full desired range of PWM levels stay available a voltage divider is no good by itself - it’s not regulated so the maximum input will go down as battery voltage declines. Instead you need a regulated voltage source, probably either an LDO or on a Zener mod driver just add a divider off of the Zener. That way you have fixed target for both high and low voltages when looking at the ADC values.

Oops, my mistake. :zipper_mouth_face:

Also look here:

if (mode_idx == 0 && PWM_LVL <= modes[mode_idx]) {

Looks like it should be:

if (mode_idx == 0 && PWM_LVL <= STEPDOWN_MINIMUM) {

i see 3 options

1. use regulated voltage reference
2. design the circuit so that you are comparing voltage of the battery with the voltage drop of the divider. Did not think this one through thoroughly though.
3. not use the full physical range of the pot, so you have some headroom to make up for the voltage drop (i.e with full battery you need to turn the pot only to 60% of it’s range to get 100% light, and with low battery you need to turn it to 100% to get 100% of the output

also the pot solution might be used with constant DC power supply, so perhaps battery is not the power source in this one at all.

Yes, all correct. (Based on who’s asking, I assume it’s a flashlight. VoB is probably looking for something like a new Lambda VaraPower.)

The ATtiny can be set to use Vcc as the reference voltage, so your #2 option is a good one assuming that don’t need to do battery monitoring. If we do need to do battery monitoring then we have to switch the Vref back and forth. I’ve already written (and posted in this thread) simple/hacky code to do that - it didn’t work correctly. I think we probably need to take two readings every time we switch the Vref, but I haven’t tried that yet.

Thanks wight, I’ll try that out tonight. :beer:

Thanks - that worked, in so far as stepping down to the STEPDOWN_MINIMUM value.

However, it continues to give the 3 periodic warning flashes, until the voltage gets down to around the 2.6 mark, where it seems to eventually peter-out.

It does not appear to be getting to the Critical routine (10 flashes & power down).

As it is now, I'm happy with the operation. I ended up increasing the time between warning flashes, as they were annoyingly frequent.

For educational purposes, I'm still interested as to why it's not getting to the Critical/Shutdown routine.

#ifdef VOLTAGE_MON
if (low_voltage(ADC_LOW)) {
// We need to go to a lower level
if (mode_idx == 0 && PWM_LVL <= STEPDOWN_MINIMUM) {
// Can't go any lower than the lowest mode
// Wait until we hit the critical level before flashing 10 times and turning off
while (!low_voltage(ADC_CRIT));
i = 0;
while (i++<10) {
PWM_LVL = 0;
_delay_ms(250);
PWM_LVL = modes[0];
_delay_ms(500);
}
// Turn off the light
PWM_LVL = 0;
// Disable WDT so it doesn't wake us up
WDT_off();
// Power down as many components as possible
set_sleep_mode(SLEEP_MODE_PWR_DOWN);
sleep_mode();
} else {
// Flash 3 times before lowering
hold_pwm = PWM_LVL;
i = 0;
while (i++<3) {
PWM_LVL = 0;
_delay_ms(250);
PWM_LVL = hold_pwm;
_delay_ms(500);
}
// Lower the mode by half, but don't go below lowest level
if ((PWM_LVL >> 1) < STEPDOWN_MINIMUM) {
PWM_LVL = modes[0];
mode_idx = 0;
} else {
PWM_LVL = (PWM_LVL >> 1);
}
// See if we should change the current mode level if we've gone under the current mode.
if (PWM_LVL < modes[mode_idx]) {
// Lower our recorded mode
mode_idx--;
}
}
// Wait 10 seconds before lowering the level again
_delay_ms(10000);
}
#endif

Probably due to an additional oversight on my part. Let’s see where I went wrong.

Hmm. Are you _certain_ that it's stepping down? To me it [now] looks pretty clear that the stepdown process is broken by the changes I suggested. It seems that I missed was this line that will continue to reset the driver to modes[0] (100% duty cycle, 255/255):

// Lower the mode by half, but don't go below lowest level
if ((PWM_LVL >> 1) < STEPDOWN_MINIMUM) {
PWM_LVL = modes[0];
mode_idx = 0;
} else {
PWM_LVL = (PWM_LVL >> 1);
}

As you can see, the line highlighted in red above should continue to reset the mode to mode zero every time we get PWM_LVL down to the point where halving it will take it below STEPDOWN_MINIMUM. Instead we should set it to STEPDOWN_MINIMUM there! Otherwise this conditional never becomes true: "if (mode_idx == 0 && PWM_LVL <= STEPDOWN_MINIMUM)" because we keep stepping down from modes[0] towards STEPDOWN_MINIMUM over and over without ever actually reaching <= STEPDOWN_MINIMUM.

Depending on what you set STEPDOWN_MINIMUM to we should be stepping down several times and then going back up, then doing it again - over and over. At least that's what I see at the moment...

Thanks wight for taking the time to explain.

I've spent a few hours with this today, but I'm not quite there yet....

I was certain it was stepping down visually, but to be sure, I charged my test cell back up to about 3.4v & hooked up an ammeter in series;

Starts out at 0.6A, ---> 3*flash/stepdown to 0.3A, then ~6 mins later, at 0.12A, another 3*flash/stepdown to 0.05A, then a few seconds later, another 3*flashes, & back up to 0.14A, then 3*flash & down to 0.02A ......./end of test...

Yep, just like you described above.

-

I replaced PWM_LVL = modes[0]; with PWM_LVL = STEPDOWN_MINIMUM , but we still don't see the Critical routine.

It now steps down as before, but doesn't jump back up & start over, just continues with the 3 flashes, maintaining the lowest current, in a loop.

Without a Babel fish, I'm still unable to properly follow what's happening to some of the variables :(

I took a couple of wild stabs ; PWM_LVL = STEPDOWN_MINIMUM -1 which done nothing, & also tried removing the line under that mode_idx = 0; which again achieved nothing.


Hmm. Please go ahead and post up your full code in some unmolested way (upload a TXT file some where or use Pastbin or a similar website). Some sites like pastebin also have a highlighter, which is nice. :slight_smile: