8-bit USB Device MCU - CH551


CH551 is an enhanced E8051 core MCU, compatible with MCS51 instruction set. 79% of its instructions are single-byte single-cycle instructions. The average instruction speed is 8~15 times faster than that of standard MCS51. CH551 supports up to 24MHz system clock frequency. CH551 has built-in capacitive touch-key detection, 3 timers and 2-channel signal capture and PWM, UART, SPI, USB device controller and full-speed transceiver and other functional modules. CH551 is a simplified MCU of CH552, with 10K program memory ROM and 512-byte internal xRAM. CH551 only has UART0. The package of CH551 is SOP16 only. CH551 does not provide ADC module or USB type-C module. Others of CH551 are the same as that of CH552, please refer to CH552 datasheet and technical resources directly.

System Block Diagram


  • Enhanced E8051 core CPU, the speed is 8-15 times faster than that of standard MCS51, with special XRAM data fast copy instruction.
  • Built-in 10KB Code Flash, 512B XRAM and internal 256B iRAM. 128B DataFlash. Support read/write by bytes.
  • Built-in 2KB BootLoader. ISP through USB or UART. ISP library is provided.
  • Built-in USB controller and USB transceiver, support USB Device mode. Support USB2.0 full-speed (12Mbps) and low-speed (1.5Mbps) transfer, support up to 64 bytes of data packet with built-in FIFO. DMA capability.
  • 3 timers/counters. 2-channel signal capture and 2-channel PWM output.
  • One full-duplex UART which is a standard MCS51 serial port supports high-baud-rate communication.
  • One SPI communication interface with built-in FIFO supports master/slave mode.
  • 6-channel capacitive detection, up to 15 touch-keys. Support independent timing interrupt.
  • 4 reset signal sources. Built-in power-on reset. Software and watchdog overflow reset, and external reset.
  • Built-in 24MHz clock source and PLL.
  • Built-in low voltage regulator from 5V to 3.3V, support 5V, 3.3V and even 2.8V supply voltage. Support low-power sleep, and support externally wake up USB, UART0, SPI0 and parts of GPIOs.
  • Unique ID.
  • Package: SOP-16.

Technical Resources

Downloading: USB interface / UART

  1. CH551DS1.PDF (CH551 datasheet)
  2. Tool: WCHISPTool_Setup.exe
  3. CH552EVT.ZIP,CH554EVT.ZIP contains:
    • CH551/2/4 reference routines (C programming language)
    • CH551/2/4 evaluation board introduction