Why a Blank CH32V005 Won't Flash Over UART - and the Two Paths That Do Work

One of the most common first-day surprises with the sub-dollar WCH RISC-V parts: you wire up PD0/PD1 to a USB-TTL adapter, hammer the chip with a UART bootloader tool, and nothing comes back. A WCH community post this week got the official explanation for the CH32V005.

The Symptom

A developer reported that a brand-new, factory-blank CH32V005D6U6 showed no response at all on the TX line when attempting to flash over the PD0/PD1 UART, and asked the obvious question: doesn't a blank chip automatically enter ISP mode?

The Official Answer

WCH staff (TECH62) confirmed the expectation to flip: a factory-blank part does not carry the UART IAP, so there is no UART bootloader to talk to until you put one there. Two working routes:

Program the IAP first via the SDI interface, after which UART flashing works - the EVT package's PUB folder documents the evaluation-board procedure step by step
Skip UART entirely: use WCH-LinkE over SDI, which the staff explicitly recommend as the direct path for the V005-class parts

The EVT package covering this family is available from the WCH downloads page (the CH32V006 EVT ZIP; the V005/V006 generation shares the tooling and documentation set). WCH also offered direct email support for follow-ups.

Cheat Sheet

Blank chip, first flash -> WCH-LinkE on SDI (recommended) or SDI-program the IAP first Chip with IAP installed -> UART bootloader on PD0/PD1 works Production programming -> WCH-LinkE fixtures over SDI; keep UART as a field-recovery path

Why This Matters for Production

The CH32V005 joins the CH32V003 ($0.1) in the sub-dollar RISC-V tier, and the same rule applies across the family: budget for WCH-LinkE programming fixtures on your test jigs, and treat the UART path as a convenience for chips that already carry IAP firmware - not as the factory-entry path. Teams burned an afternoon on this in 2024 and 2025 with the V003; the V005 generation behaves the same way, and now you have the vendor's word on it.

Source: CH32V005空片不能通过UART烧录吗？ - WCH BBS thread 161658. Condensed and translated from the public WCH community discussion.