I don't know if I have enough pins on my Xiao ESP32-C3 I have three DRV8255's, and SD Card Reader (SPI), 4x push buttons, 2x endstops, 1x mosfet pin to fire a connected dc fan

---

Probably not, at least not directly from GPIOs alone on a Seeed Studio XIAO ESP32-C3.

Here’s the rough pin budget.

Available GPIOs on the XIAO ESP32-C3

You realistically get about 11 usable GPIOs once you account for boot/USB considerations.

Your devices
3× DRV8255 motor drivers

A DRV8255 brushed DC driver usually needs:

2 pins per motor (IN1 + IN2) for direction/PWM
or
sometimes 1 PWM + 1 DIR

So:

Minimum realistic: 6 GPIOs
Could become 9 if using enable/fault/sleep separately
SD Card Reader (SPI)

SPI shares most lines:

MOSI
MISO
SCK
CS

That is:

4 GPIOs total
Push buttons
4 GPIOs

(Unless multiplexed)

Endstops
2 GPIOs
MOSFET for fan
1 GPIO
Total
Device	Pins
3× DRV8255	6
SD Card SPI	4
4 buttons	4
2 endstops	2
Fan MOSFET	1
Total	17 GPIOs

And that’s before considering:

UART debug
reserved boot pins
fault pins
LEDs
future expansion

So on a XIAO ESP32-C3, you are short by roughly 6 pins.

Best solutions
Option 1 — Add an I/O expander (recommended)

Use:

MCP23017
or PCF8574

This is the cleanest approach.

Move:

buttons
endstops
maybe fan control

onto the expander.

Then you only use:

SDA
SCL

from the ESP32.

Option 2 — Use resistor ladders for buttons

4 buttons can become:

1 analog pin

using different resistor values.

Good if you are desperate for pins.

Option 3 — Use fewer control pins per motor

If you only need:

forward/off
no braking
no reverse

then each DRV8255 could use:

1 PWM pin

But if you need full bidirectional control, assume 2 pins each.

Option 4 — Bigger ESP32 board

Honestly, depending on enclosure constraints, something like:

ESP32 DevKit V1
ESP32-S3 DevKitC

may save you a lot of pain.

The XIAO is excellent for compact builds, but you’re already beyond its comfortable GPIO budget.

My recommendation

For your setup:

Keep the XIAO ESP32-C3
Add an MCP23017
Put buttons + endstops on the expander
Keep motors and SPI directly on ESP32 pins

That should fit comfortably.

---

I have designed a resistor ladder for buttons and endstops. Should resistor values increase or does it matter? The remaining ESP32C3 pins?

---

For a resistor ladder used with a single ADC pin on the Seeed Studio XIAO ESP32-C3, the actual direction of resistor values does not fundamentally matter — what matters is:

each button/endstop produces a distinct, well-separated voltage
the voltages stay within ADC range
the impedance is not excessively high
The important part

You want ADC readings that are:

stable
far apart
monotonic/predictable

For example:

Button	ADC Voltage
None pressed	3.3V
Button 1	2.7V
Button 2	2.1V
Button 3	1.5V
Button 4	0.9V
Button 5	0.3V

The resistor ordering itself is irrelevant if those voltages are clean.

Recommended topology

The usual approach is:

pull-up resistor to 3.3V
each button switches a different resistor to GND

Like:

3.3V
 |
[10k]
 |
ADC ---- button1 ---[1k]--- GND
 |
 +---- button2 ---[2.2k]--- GND
 |
 +---- button3 ---[4.7k]--- GND
 |
 +---- button4 ---[10k]---- GND

This works well because:

“no press” = full 3.3V
each press lowers voltage differently
Important ESP32-C3 caveat

The ESP32 ADC is:

noisy
non-linear
not precision-grade

So:

do NOT make voltages too close together
avoid equal spacing assumptions
leave generous margins

Aim for:

at least ~300–400 ADC counts separation
maybe more
Resistor sizing guidance

Avoid:

extremely small resistors (<220Ω)
wastes power
extremely large values (>100kΩ effective impedance)
ADC becomes unstable

Good practical range:

pull-up: 4.7k–22k
ladder resistors: 1k–47k

A total impedance around:

5k–20k effective
is usually comfortable.
Important limitation

A resistor ladder only works reliably if:

ONE button/endstop is active at a time

If multiple switches can trigger simultaneously:

voltages combine
decoding becomes ambiguous

For endstops this may matter depending on mechanics.

About your remaining ESP32-C3 pins

Assuming:

Use	Pins
3 DRV8255s	6
SPI SD card	4
resistor ladder ADC	1
fan MOSFET	1

Total:

about 12 pins

That is very close to the practical limit on the XIAO ESP32-C3, but now potentially achievable depending on:

which pins are usable
whether SD card and boot pins overlap safely
whether you need UART/debugging

You are now in “careful pin assignment” territory rather than “impossible.”

---

redo diagram with button5 and button6 (endstops)

---

Here’s a corrected resistor ladder diagram including Button 1–4 + Button 5/6 (endstops).

I’ll assume:

1 ADC input pin on the Seeed Studio XIAO ESP32-C3
pull-up to 3.3V
each button pulls the ADC to GND through a unique resistor value
only one input active at a time (important assumption)
Updated resistor ladder (6 inputs)
3.3V
 |
[10k pull-up]
 |
 +-------------------- ADC (ESP32-C3)
 |
 |---- Button 1 ----[1k]----- GND
 |
 |---- Button 2 ----[2.2k]--- GND
 |
 |---- Button 3 ----[4.7k]--- GND
 |
 |---- Button 4 ----[10k]---- GND
 |
 |---- Button 5 ----[22k]---- GND   (Endstop A)
 |
 |---- Button 6 ----[47k]---- GND   (Endstop B)
How this behaves
Input	Approx voltage trend
none pressed	~3.3V
BTN1	highest drop
BTN2	slightly higher
BTN3	mid
BTN4	lower-mid
BTN5	low
BTN6	very low (closest to GND)
Why resistor spacing is OK here

Your ESP32-C3 ADC:

is noisy
has non-linear regions near extremes

So the key design choice is:

non-linear spacing is GOOD
bigger gaps at low voltages help stability

Your ladder is actually better than evenly spaced values.

Critical improvement (strong recommendation)

Add one of these:

Option A — capacitor smoothing (simple)

Place:

100nF from ADC pin to GND

This:

reduces jitter
stabilises endstop reads
Option B — software hysteresis (required)

Use thresholds like:

BTN1: 3000–3200
BTN2: 2500–2900
BTN3: 1900–2400
BTN4: 1200–1800
BTN5: 500–1100
BTN6: 0–400

Add:

debounce time (20–50 ms minimum)
One more subtle issue (important)

Endstops often trigger simultaneously (mechanical safety cases).

If both BTN5 + BTN6 can ever be pressed together:

the ladder becomes ambiguous (voltages combine)

If that is possible in your system, you should:

move endstops off the ladder
or isolate them digitally (preferred for safety-critical signals)
If you want next step

I can:

map this onto actual ESP32-C3 safe GPIO assignments
check your DRV8255 pin budget realistically
or
redesign the whole system so you don’t run out of pins again (you’re close but still salvageable)

---

but I doubt the values are distinct enough, how to make a permutation table for different combination presses?

---

You’ve hit the key limitation of resistor-ladder encoding: once multiple switches can be pressed, it stops being a “6-state system” and becomes a 2⁶ = 64-state analog system.

So yes — you can build a permutation table, but it only works if:

the ADC is stable enough
resistor tolerances are tight (1% or better strongly recommended)
you accept calibration complexity
1. The core idea: it becomes a parallel resistance problem

Each button adds a resistor to GND. The ADC sees:

a pull-up resistor to 3.3V
multiple possible resistors to GND in parallel

So the effective resistance is:

R
eq
	​

=(∑
i=1
n
	​

R
i
	​

1
	​

)
−1

Then voltage is:

Option B — GPIO expander

MCP23017
gives 16 clean digital inputs over 2 wires
Option C — keep ladder ONLY for buttons, not endstops

Endstops should be:

binary
deterministic
safety-critical

So they really should NOT share ADC encoding.

7. Bottom line

You can build a permutation table, but:

mathematically: works (64 states)
electrically: fragile
practically on ESP32-C3 ADC: unreliable at scale

If you want, I can:

compress your 6 inputs into a robust 3-pin matrix design
or
redesign the whole IO map so your DRV8255 + SD + inputs fit cleanly without analog decoding risk

---

Compress my 6 inputs into a robust 3-pin matrix design

---

assistant

Good direction—moving off the ADC ladder and into a digital scan will immediately make the system more deterministic on the Seeed Studio XIAO ESP32-C3.

You can compress 6 inputs into 3 GPIOs in two practical ways. One is a true matrix, the other is a hybrid scan that behaves better for endstops.

Option 1 (recommended): 3×2 button matrix (6 buttons exactly)
Wiring concept

You use:

3 GPIOs as columns (outputs)

2 GPIOs as rows (inputs with pull-ups)

That gives:

3 × 2 = 6 unique buttons

exactly your requirement

Wiring diagram
Columns (outputs)              Rows (inputs w/ pull-ups)

GPIO_A  ---- BTN1 ----+
GPIO_B  ---- BTN2 ----+------ GPIO_R1
GPIO_C  ---- BTN3 ----+

GPIO_A  ---- BTN4 ----+
GPIO_B  ---- BTN5 ----+------ GPIO_R2
GPIO_C  ---- BTN6 ----+

Each button connects:

one column line

one row line

So pressing a button shorts one row/column intersection.

Pin behaviour
Columns:

Set HIGH one at a time (scan)

Others LOW or Hi-Z

Rows:

Input with pull-up

Read LOW when button in active column is pressed

Scan logic

Pseudo:

C
for (col in columns):
    set_all_columns_low()
    set(col, HIGH)

    delay(2-5 microseconds)

    read rows:
        if row1 LOW → button (row1,col)
        if row2 LOW → button (row2,col)
Mapping
Row \ Col	A	B	C
R1	BTN1	BTN2	BTN3
R2	BTN4	BTN5	BTN6
Why this is robust

Compared to resistor ladder:

Advantages

immune to ADC noise

deterministic digital reads

no calibration needed

multiple presses are cleanly identifiable

ESP32-C3 friendly

uses only GPIO logic

no analog quirks

no voltage thresholds

Option 2: 3-wire “binary encoded ladder” (not recommended here)

You could encode 6 states in binary (3 pins → 8 states), but:

requires diode isolation per button

becomes complex fast

endstops + buttons mix poorly

So I would not use it for your case.

Where endstops go (important)

You mentioned endstops earlier.

Do NOT put endstops in the matrix.

Reason:

endstops are safety signals

matrix scanning introduces latency (~1–5 ms worst case)

ghosting risk if wiring ever changes

Best practice:

keep buttons in matrix

keep endstops as direct GPIO inputs (or GPIO expander)

Minimal clean architecture for your system

Given your full setup:

3× DRV8255 drivers

SD card (SPI)

fan MOSFET

2 endstops

6 buttons

Recommended split:
Matrix (3 GPIO)

6 buttons

Direct GPIO

2 endstops

fan MOSFET

DRV8255 control pins (as needed)

SPI

SD card (4 pins)

This keeps everything deterministic and avoids analog entirely.

Key improvement insight

What you originally tried (ADC ladder) is:

“compress signal space into voltage domain”

What matrix gives you is:

“expand combinatorial space using time multiplexing”

Much more suitable for microcontrollers like ESP32-C3.

If you want next step, I can:

map your entire ESP32-C3 pinout safely (avoiding boot strapping issues)

or
optimise DRV8255 pin usage so you don’t run out again

or
design a “no-conflict wiring plan” for the whole system

---

assistant
Assuming the standard ladder topology:

Pull-up: 10 kΩ to 3.3 V

One button pressed at a time → a single resistor to GND

ADC reads the divider node

So each case is:

V
ADC
	​

=3.3⋅
R
pullup
	​

+R
eq
	​

R
eq
	​

	​


Where R
eq
	​

 is just the pressed resistor (since only one is active).

Given values

R
pullup
	​

=10kΩ

V
CC
	​

=3.3V

Pressed resistors:

B1 = 1kΩ

B2 = 2.2kΩ

B3 = 4.7kΩ

B4 = 10kΩ

B5 = 22kΩ

B6 = 47kΩ

ADC voltages (single press only)
B1 = 1kΩ

V=3.3⋅
10000+1000
1000
	​

=3.3⋅0.0909≈0.30V

B2 = 2.2kΩ

V=3.3⋅
12200
2200
	​

=3.3⋅0.1803≈0.59V

B3 = 4.7kΩ

V=3.3⋅
14700
4700
	​

=3.3⋅0.3197≈1.06V

B4 = 10kΩ

V=3.3⋅
20000
10000
	​

=3.3⋅0.5=1.65V

B5 = 22kΩ

V=3.3⋅
32000
22000
	​

=3.3⋅0.6875≈2.27V

B6 = 47kΩ

V=3.3⋅
57000
47000
	​

=3.3⋅0.8246≈2.72V

Final table (clean view)
Button	Resistance	ADC Voltage
B1	1kΩ	~0.30 V
B2	2.2kΩ	~0.59 V
B3	4.7kΩ	~1.06 V
B4	10kΩ	~1.65 V
B5	22kΩ	~2.27 V
B6	47kΩ	~2.72 V
Important interpretation (this is the key part)

You now have:

Range: 0.30 V → 2.72 V

Spread: fairly good

BUT:

ESP32-C3 ADC reality:

non-linear curve (especially above ~2.5V)

noise ±20–50 mV typical without filtering

temperature drift

So the danger zones are:

B5 vs B6 (closest spacing in ADC “count space”)

high end compression near 3.3V

Practical recommendation

If you want this to be reliable:

1. Add hardware smoothing

100nF capacitor at ADC pin

2. Add software hysteresis

±100–200 ADC counts per button bucket

3. Increase spacing if unstable

If B5/B6 collide in testing:

change B6 → 68k or 100k

If you want next step, I can convert these voltages into ESP32-C3 ADC counts + recommended thresholds, which is usually where this design either becomes solid or breaks.

---

user
and if no buttons are pressed?

---

assistant
With your topology (10k pull-up to 3.3 V, and each button connects a resistor to GND), “no button pressed” means:

ADC node is only connected to 3.3 V through the pull-up

no path to ground

so essentially no current flows

No-button voltage

So the ADC node is simply:

V
ADC
	​

=V
CC
	​

=3.3V

Final state table (including idle)
State	Resistance to GND	ADC Voltage
No buttons pressed	open circuit	3.3 V
B1	1kΩ	~0.30 V
B2	2.2kΩ	~0.59 V
B3	4.7kΩ	~1.06 V
B4	10kΩ	~1.65 V
B5	22kΩ	~2.27 V
B6	47kΩ	~2.72 V
Important implication

This is actually very useful:

“no press” becomes a distinct top-level state

gives you 7 total states (including idle)

simplifies firmware classification

So your decoder becomes:

1 idle state + 6 button states

One caution (important on ESP32-C3 ADC)

On the Seeed Studio XIAO ESP32-C3:

3.3 V is near ADC full-scale

many ESP32 ADCs saturate or compress near the top end

So practically:

“no press” might read closer to ~3.0–3.3 V but not perfectly stable

👉 You should treat idle as a range, not a single value:

e.g. 2800–4095 ADC counts (depending on attenuation setting)

If you want, I can next:

convert all of these into actual ESP32-C3 ADC counts (0–4095 scale)

and
give you robust threshold bands so it never misfires in real firmware

---

user
Now calculate the voltage read at the adc pin if button 1 and button 2 are pressed. And also in the case that button 1 and button 3 are pressed.

---

assistant
Now you’re in the parallel-resistance regime, so the node voltage is no longer a simple divider — it depends on the equivalent resistance of the pressed resistors in parallel.

We’ll keep your circuit assumptions:

Pull-up: R
PU
	​

=10kΩ

V
CC
	​

=3.3V

Buttons connect resistors from ADC node → GND

Multiple presses = resistors in parallel

Core equations

Equivalent resistance:

R
eq
	​

=(
R
1
	​

1
	​

+
R
2
	​

1
	​

)
−1

ADC voltage:

V
ADC
	​

=3.3⋅
R
PU
	​

+R
eq
	​

R
eq
	​

	​


Case 1: B1 + B2 pressed
Step 1: parallel resistance

B1 = 1kΩ

B2 = 2.2kΩ

R
eq
	​

=(
1000
1
	​

+
2200
1
	​

)
−1
=(0.001+0.0004545)
−1
=687.5Ω

Step 2: ADC voltage

V
ADC
	​

=3.3⋅
10000+687.5
687.5
	​

=3.3⋅0.0643≈0.212V

Case 2: B1 + B3 pressed
Step 1: parallel resistance

B1 = 1kΩ

B3 = 4.7kΩ

R
eq
	​

=(
1000
1
	​

+
4700
1
	​

)
−1
=(0.001+0.0002128)
−1
≈822.8Ω

Step 2: ADC voltage

V
ADC
	​

=3.3⋅
10000+822.8
822.8
	​

=3.3⋅0.0761≈0.251V

Summary table
Combination	Req (Ω)	ADC Voltage
B1 + B2	~687 Ω	~0.212 V
B1 + B3	~823 Ω	~0.251 V
Critical insight (this is the key engineering point)

Notice what happens:

B1 alone: ~0.30 V

B1 + B2: ~0.21 V

B1 + B3: ~0.25 V

So combinations:

✔ collapse into lower voltage region
✔ cluster very tightly
❌ become hard to distinguish on ESP32 ADC
Why this matters on ESP32-C3

On the Seeed Studio XIAO ESP32-C3:

ADC noise ≈ ±20–80 mV typical

these differences (0.21 vs 0.25 V) are inside noise band

So:

multi-button detection with this ladder is not reliably separable in practice

Practical conclusion

Your design works well for:

single-button detection (6 states + idle)

But breaks for:

multi-button encoding (2⁶ permutation space)

If you want next step, I can:

compute the full 64-state voltage table (and show actual collision clusters)

or
redesign this so you can safely detect multi-presses without losing GPIOs (there is a clean hybrid solution for your setup)