Bench test C of 5 · microSD

microSD on its own SPI bus

2 pads to solder Power: 5 V 3 A on U6, not the laptop Have ready: FAT32 card, 32 GB or less

What you add The blue SPI microSD module

What passing proves The card mounts, reads, writes and keeps up with audio

Already working A: chip, PSRAM, amp at 0x2D · B: both speakers

TipThe module keeps driving MISO even when it isn’t selected, so it gets four pins of its own. Tests C and D can never get in each other’s way.

Wiring · test C · 6 wires · 2 pads to solder

Louder-ESP32-S3 · K1 nothing modified

test C

microSD module SPI · XC6206 · labels say SO and SI

Same board wired in test B

test B

Supply + 2 speakers already in place

 Test D · PN532 readerP1 and P2 sockets, no soldering 

 Test E · knob and buttonssockets + pads SD 39, RGB OUT 21, IR IN 07 

 power ground signal later steps pad = solder · pin = header pin · socket · screw = terminal 

 Pin budget · Louder-ESP32-S3 rev K1 4 of the build's 13 GPIO wired after test C 

Tap a pin to see why it’s free, used or off limits.

 this step earlier step later step free on the chip, pad not checked avoid 

0, 3, 45, 46 strapping pins: they decide how the chip boots
8, 9, 14–17 wired on the board to the TAS5805M amp
19, 20 USB: flashing and the serial console
26–37 flash and octal PSRAM inside the N8R8 module
7 usable, but it shares the IR receiver
43, 44 UART0: fine for the SD card, the console moves to USB

Wire it, then check before power

0 of 5

Header soldered flat into WS 40 and CLK 41 in the R mic circle. No bridge between the two.
SI to WS 40, SCK to CLK 41, SO to 43, CS to 44, GND to the UART GND. Each checked against the label at both ends.
VCC on the + screw of U6, together with the red supply wire. Not on 3V3.
⚠ Caution · no fuse on this board The barrel jack and U6 share the same two nets, and the M7 diode clamps across the rail. A reversed supply conducts straight through it. Meter first, plug second.
Supply metered at U6 before it goes in: + to +.
Card formatted FAT32, any file dropped in the root.

Flash and check

Power: 5 V 3 A supply on U6

pio run -e c_sd -t upload -t monitor

Or flash it from the browser, desktop Chrome or Edge, with the build note. Blank board? Do the first flash once.

What you should see

TEST C - microSD
card : SDHC, 30528 MB
root:
 4213 test.txt
write : ok
read back: written by test C
write rate: 480 kB/s over 1065 ms
TEST C done.

Pass: the card mounts, the file list matches, and the write reads back. A 128 kbps MP3 needs 16 kB/s; anything in the hundreds is fine.

On my bench

✓ PASSED ON THE PADS · SANDISK ULTRA 32 GB · 371 KB/S · MISO ON 43, CS ON 44 · VCC ON 5 V

It passed on the P1/P2 sockets first (c_sd_sockets, 376 kB/s), then on the pads. The UART header on my board already has pins; if yours is bare, that’s three more pads.

What went wrong on my bench

CS and MISO came out the reverse of the plan. the plan c_sd_scan tried both and found MISO on 43, CS on 44. Everything on this page already uses them.
The module holds MISO even when it isn’t selected. the module Its buffer’s output-enable is tied on. Rather than modify it, the card gets its own pins.
The card never answered its first command. me Every time it was wiring: pins in bare holes without solder, two wires swapped, one a position off. Run c_sd_sockets on P1/P2 first to rule the pads out.
An older sheet said 3.3 V would starve the card. the plan It assumed an AMS1117. This module has an XC6206, so 3.3 V works. 5 V from U6 still leaves more headroom.

If yours fails

GO_IDLE_STATE failed / cmd: 0x00: Wiring. Check each wire against the label at both ends, one at a time.
MOUNT FAILED: In order: module on 3.3 V instead of 5 V; MISO and MOSI swapped; a dry joint; an exFAT card. Cards above 32 GB usually arrive exFAT.
Mounts, then errors mid-file: Wire length or a poor ground. Shorten everything; give the module its own ground.
Works cold, fails after test B ran: Supply current. Use the 3 A adapter for this test too.

Next · test D The PN532 reader. Six jumpers into the sockets, no soldering on the board. Go to D →