Turn-key PCB assembly services in prototype quantities or low-volume to mid-volume production runs

AVR Fuse Reset with HVSP

If you have been working with AVR, you know about the concept of fuses. They are mainly responsible for deciding the clock source and also the JTAG feature. However, if you program them wrong, your chip would no longer be programmed using an ISP. As a solution to this, there exist a circuit which can rest your fuses just by a push of a button using high voltage serial programming. This method normally applies to the chip which lacks pins to use high voltage parallel programming. A 12V power supply, along with a transistor, a regulator and a ATtiny2313 is needed to control the circuit. 4 seven segment displays are also required for feedback and a normal push-button for control. Upon attaching power firmware reads target MCU device signature via AVR’s HVSP (High-Voltage Serial Programming) interface. It then look up the device name by matching the device signature and on a press of a button it simply write the factory default settings for the chip. This is a must have thing for all the AVR users particularly the beginners. You… Continue reading

Reset TinyAVR fuses with HVSP

AVR Tiny microcontrollers have a low pin count (8 or 14). Sometimes you want to all of them including Reset pin which can be turned in to normal I/O pin. But problem is that after this operation AVR becomes no longer programable bia SPI. The only trick is to use High Voltage (HV) programmer. In this case serial. So you can first program AVR via SPI, then change RESET fuse to be as I/O and revert again if reprogram is needed. And of course using HV programming mode it is convenient to reset fuses of bricked AVRs. Continue reading