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Comment by NortySpock | Hacker News Reader

RISC-V for $4.30 USD? Sounds like they'd sell like hotcakes...

NodeMCU ESP32-C3S_KIt

Specifications: Wireless module – AI Thinker ESP32-C3S (footprint compatible with ESP32-S / ESP32-WROOM-32D) with ESP32-C3 RISC-V processor @ 160 MHz, 2.4 GHz WiFi, Bluetooth 5.0 LE, 4MB flash, on-board PCB antenna, and IPEX connector (which may be soldered or not). USB – Micro USB port for power and programming via CH340C USB to TTL chip Expansion – 2x 15-pin headers with GPIO, SPI, UART, ADC, I2S, 3.3V, GND Misc – RGB LED, Reset key, user-programmable key Dimensions – 49 x 26 mm

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Look at the solder joints. How can they mass produce hand-soldered PCBs at that price?

X marks the spot.

Slave labor.

Or could be super low commodity prices.

Through-hole components like headers can be soldered by selective solder machines, for example: https://www.youtube.com/watch?v=2sm_qdeconI or https://www.youtube.com/watch?v=oaJ67KUOHiYhttps://www.youtu... They use a little 'fountain' of molten solder that's controlled by cnc to touch each component and solder it in place.

The solder joints pictured are all rough enough to have been hand soldered by a beginner, though.

Most of these cheap boards are sold with the headers not soldered on.

My comment was about all solder joints, not just the headers.

Easily, at 10 seconds per board, you get ~350 boards per hour at around ~$15 per hour.

I'd add 400kb SRAM to the spec list.

Full data sheet: https://www.espressif.com/sites/default/files/documentation/...

When did ESP 32 switch to RISC-V? Are there any comparisons on how the change impacts performance?

There’s no “switch” (yet), the C3 is their new MCU with a RISC-V core, but they will be continuing to manufacture their Xtensa-based designs for some time.

They didn't switch to RISC-V. The added RISC-V. Their recent releases have been a mix:

September 2019: ESP32-S2. Single core Xtensa LX7.

November 2020: ESP32-C3. Single core RISC-V.

December 2020: ESP32-S3. Dual core Xtensa LX7.

April 2021: ESP32-C6: Single core RISC-V.

Didn't know the differences between the original ESP32 and the ESP32-S3, so I looked it up. The ESP32-S3 is basically an updated version.

Major differences:

Xtensa® dual-core 32-bit LX6 vs LX7 (better FPU I think?)

BR/EDR + Bluetooth LE v4.2 vs Bluetooth LE v5.0

SRAM 520 vs 512

ROM 448 vs 384

USB OTG none vs 1

Plus some minor differences in the peripherals.

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