NXP’s PN7120 is NFC controller for contactless communication at 13.56MHz. It interfaces with the host CPU via the I2C bus. The I2C slave address of  PN7120 is 0b010100Lx, where L is a configurable LSB of the address (by pin B2,...

Once upon a time, I decided it is a good time to upgrade the version of gcc compiler we use in our ARM926-based firmware project. Historically, this project uses gcc version 4.6, which is quite outdated nowadays (January 2018). In...

The X86 has always supported unaligned accesses. In the ARM world the first architecture that supported unaligned accesses in hardware was ARMv6. The architecture was implemented in the ARM11 core around the year 2002 and onward. There is an excellent...

This is Part 2 of a two-part series on Ethernet RMII. In Part 1 I described my hardware setup and basic Ethernet operation. In the second and final part I will describe the design of specialized MAC cores I implemented...

This is Part 1 of the two-part series on Ethernet RMII. Part 2 is also available. Imagine your application requires a non-standard periphery controlled by an embedded processor. What options do you have? The periphery can be implemented in an...

How to export PCB design from the free Altium Circuit Maker v1.0.4 so that it can be submitted to OSH Park fab. This took me an evening to figure out; OSH Park service was bitching about missing “outline” and/or drill...

  [half-way through; click a pic to see hi-res] [connections to bga] [finished “product”] And it (almost) worked! Though not at-speed, because of wire inductances.

During pre-Christmas sale on Seeed Studio Bazaar  they offered these digital radio modules with the nRF24L01+ chip for only US$0.81 each. So I bought 10 of them outright What would YOU  suggest to do with them? Build a wireless flower...

This issue bugged me a long time, finally I solved it this evening. Debugging code on my PIP-Watch using my ST-LINK-v2 JTAG debugger was very painful because the debugger software — OpenOCD and GDB — kept failing randomly during debug...

In previous post we discussed CPU power consumption in PIP-Watch. Today we look into Bluetooth power consumption because it is significant as much as the CPU power. Bluetooth Radio States Practically the only significant part that consumes a lot of...

Processor Power The PIP-Watch is a battery-powered device that will be continuously on, hence the average power consumption is one of the most important engineering aspects. In this post I will go through two simple steps of optimizing CPU power...

The printed circuit boards for PIP-Watch Zero came from Pragoboard fab on Friday 12 Sept. I ordered three pieces because the cost is practically identical as for two or one. On Saturday I assembled one board, and on Sunday I...