COVID-19 is by far not over, and in Switzerland the infection rate is going up again (2nd wave?). During the spring 2020 semester university lock-down we moved pretty much everything to a ‘distance learning’ setup. With that experience and with the request to prepare for the fall semester, I have constructed a DIY conference and teaching device which should make things simpler and easier: a combination of video camera, speaker phone and a muting device
Yeah, the LCD is tiny at 2.4″, and the emulation runs about 15% slower than an NTSC C64. But it’s running on a small embedded board that’s available for under $30 US (DigiKey, Mouser, …) including mounted LCD display and USB OTG jack. Just add keyboard, OTG USB adapter, and power supply. This is a port of my portable C64/6502 emulator for terminal console, which was a port of my Commodore/6502 emulator for Windows Console. But this time, I dropped the console part, and went for real video (LCD) and USB keyboard support. Hello PETSCII!
The approach I took was a mixed signal one where a capable analog front end would be paired up with a beefy DSP processor to compute the Impedance. Most importantly, in this scheme, the DSP is responsible for discriminating the phase between the sampled voltage and current waveforms; this approach is preferred because it leads to good accuracy and calibration stability.
Murata produces LoRa module CMWX1ZZABZ-xxx based on SX1276 transceiver and STM32L072CZ microcontroller. The soldering of the LGA module is not very hobby-friendly. I constructed small breakout PCB for this module with additional buck/boost switcher and place for SMA connector. The transceiver features the LoRa®long-range modem, providing ultra-long-range spread spectrum communication and high interference immunity, minimizing current consumption. Since CMWX1ZZABZ-091 is an “open” module, it is possible to access all STM32L072 peripherals such as ADC, 16-bit timer, LP-UART, I2C, SPI and USB 2.0 FS (supporting BCD and LPM), which are not used internally by SX1276.
The defacto ‘hello world’ for microcontrollers is blink a LED at a steady rate. This is exactly what I’m going to do today. I made a small 5×5 development board, soldered it up and started programming. In this first example we not gonna use fancy IRQs or timers to blink at a steady rate, but we insert NOPsas delay. This would give an idea of the RAW performance of the chip. The used code is simple; set up the maximum available clock available and then toggle RA0 for ever.
Sjaak wrote about a Chinese ARM chip compared to a ST ARM chip:
Most of us do know the ST line of ARM chips called STM32. They come in multiple flavours and the STM32F103 is one of the most common entry level family of chips. They are called by ST as mainstream. They are a full featured 32 bit ARM Cortex M3 chip running at max. 72MHz with all the requisite peripherals like ADC, DAC, USB, CAN, I2C, I2S, SPI, SDIO, PWM, RTC, interrupts and various timers. Lets zoom into the STM32F103C8 chip (which seems the be the go-to choice of the Chinese el-cheapo development breakout boards)