OSHW clock kit with 22 cents Nuvoton enhanced 8051 microcontroller N76S003 - Page 1
Forum section: electronics / general

author: danchouzhou
author_rank: Contributor
timestamp: January 19, 2025, 11:59:44 am
content: This is an open-source project I've completed over the past few months - a clock kit based on the Nuvoton N76S003.https://github.com/danchouzhou/003ClockN76S003 is an enhanced MCS-51 microcontroller with a mechanical cycle of 1T, meaning the instruction with the unit of clock cycles, and instructions are fully compatible with the standard model. Thus, at the same clock rate, the processing speed is much faster than the standard model. The 18 KB program memory can also be partitioned as data flash for storing data or maintaining memory when powered off. Additionally, it includes two sets of UART, SPI, I2C, ADC, and PWM, which are all popular and commonly used hardware peripherals.Besides having clock and timer functions, this kit has all the IO pins designed on the circuit board, giving it excellent expansion capabilities. This allows for more functions based on the same hardware, such as a temperature and humidity meter, voltage and current power meter, engine tachometer, and more - these are functions I've thought of for now, and I might develop them in the future.The circuit board design refers to the approach in this article, which staggers the pin header footprints. This allows us to directly insert the pin headers without soldering pin sockets, maintaining the tidiness of the appearance.https://hackaday.com/2021/08/12/who-needs-pin-headers/Additionally, I've established a compilation environment using the open-source VS Code and SDCC (Small Device C Compiler). You only need to install SDCC and programming software, and open this project in VS Code as a folder to start writing programs and add your desired features. (Refer to the README.md on GitHub)I named this project 003Clock because it can use N76S003, is pin-to-pin compatible with the M2003 which is a 32-bit Cortex-M23 microcontroller, and the previously launched N76E003 by Nuvoton. Other 8051 series by Nuvoton, such as the MG51 and MS51 series, are also compatible. I believe Nuvoton named this microcontroller as 003 because it is pin-to-pin compatible with the STM8S003 and offers a better price advantage.In Taiwan, I sell complete kits online, including all parts. Please forgive me for not being able to sell the kits to other countries at the moment, but I consider this an open-source project, and all designs are on GitHub. If you're interested in this project, feel free to download and build it yourself.As far as I know, Nuvoton chips are available on the official eStore “Nuvoton Direct”, TECHDesign, and DigiKey, which should be accessible in all countries. The other parts should not be too difficult to obtain.https://direct.nuvoton.com/en/n76s003-series/https://www.techdesign.com/market/nuvoton/product-detail/ntc000715/n76s003at20https://www.digikey.com/short/7tz04djwLeave a comment below if you have any suggestions or questions about the project, I’m happy to share with each other.

author: I wanted a rude username
author_rank: Frequent Contributor
timestamp: January 19, 2025, 05:34:17 pm
content: Cool! Nice clean hardware design. I like those Nuvoton 8051s ... good value and sensible peripherals.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: April 28, 2025, 06:43:19 am
content: Quote from: danchouzhou on January 19, 2025, 11:59:44 amNifty, but looks to use a somewhat ordinary oscillator at 50ppmYou could look at a part like TG-3541CE-32-7680KXA3, which is 1.5-5V 32.768kHz with 1.9ppm over 0-50'C, that can drive as external count into T0 or T1 pin,with TH0 OR'd to give your 1 or 2 Hz interrupt rateOr for more general use, you could chase down 'lowest price TCXO' and adapt things. With LED display, you do not care about uA vs 2mA.At lcsc we findTCXO 26c/30+,https://www.lcsc.com/product-detail/Temperature-Compensated-Crystal-Oscillators-TCXO_Seiko-Epson-X1G0042110003_C3013793.html0.5ppm = -30 ºC to +85 ºC and 1ppm/Year aging. 3V and Clipped sine, so use a low cost xx2GU04 ac coupled buffer to drive the MCU.If 26MHz is marginal on a 24MHz MCU, you can use /2 CLKDIV choice for 13Mhz sysclk.Other choices:1XTV12800MDA 12.8MHz Clipped sine 0.5ppm KDS Daishinku SMD3225-4P VC-TCXO C3345189 60c/30+Or VC-TCXOTKD-TC20D026000GECC111 C20607966 VCTCXO 26MHz Clipped sine 2v8 0.5ppm 1ppmYr 138dB 2016 32c/30+1XTV16320JAA_C2788191 VCTCXO 16.32MHz Clipped sine 3v3 0.5ppm 1ppmYr 3225 82c/30+With a VC-TCXO, you can use a trimpot to trim the oscillator frequency post-soldering, for least error.Or if you want a simple CMOS out, better TC than the ±50ppm, and higher MHz version to match the MCU:XO32C024000GBHE003 TKD 1.8V~3.3V ±10ppm 24MHz CMOS SMD3225-4P C20617237 26c/100huaxindianzi-3Y024000VP C19725352 24MHz CMOS 1.8~3.3 ±10ppm 2ppmYr 3225 18c/50or better tempco, and wider Vcc, with Curves in the data sheet.SX3M16.000A10F20TNN Shenzhen SCTF Elec 1.8~5V ±10ppm ±20ppm 16MHz CMOS SMD3225-4P C41361431 31c/30SX3M20.000A10F20TNN Shenzhen SCTF Elec 1.8~5V ±10ppm ±20ppm 20MHz CMOS SMD3225-4P C41361433 35c/30Notice that these days, there is not much premium for a TCXO or even VC-TCXO, but they do need a 2GU04 SOT363 buffer.