2017-07-18
So many failures, so little time More failures. Apparently the driver IC I chose to drive the digital outputs is an N-channel driver. Naturally I had it trying to switch +24V. I know what you’re saying: hey Vic, you stupid, you’ll need a charge pump in order to bring the gate voltage above the source voltage. I did not have nor am I willing to incorporate a charge pump. Another failure was failing to properly Read more…
2017-06-24
The turkey has landed The boards have arrived and the lost Digi-key order has been retrieved. The folks where the package was erroneously delivered were kind enough to reach out to me and I picked it up from them. Assembly wasn’t terrible. Almost everything fit perfectly. I must have double-dosed my stupid pills the day I laid out the pads for the fuse holders. Apparently they’re 9mm wide and I, for some reason, allocated 6mm Read more…
2017-06-18
Well the boards have been lost in shipment along with a Digi-Key order. Two orders in the span of two days. Not even properly lost. They were delivered to the wrong address. Through complete and total incompetence of the USPS I received junk mail destined for 1234 Street A. I live on 1234 Street B. According to Google maps that’s a neighborhood two streets over so it’s probably the same mail route. Put two and Read more…
2017-06-12
With all this extra time on my hands while waiting for the PCB to come back, instead of working on the house, playing with the dog, interacting with family, or doing a push-up I decided to test some of the circuitry I’ve already sent off for fabrication. The portion of the circuit under test this time was the the over-voltage crowbar circuit. The basic idea is that if the voltage goes above spec, 5.5V for Read more…
2017-06-08
The design of the power and serial cape is done. The components have been ordered. I will wait until the IO board comes back and the components come in before sending the cape off to fab. Juuuuust to make sure I didn’t screw up some minute detail that renders the design useless. Additionally, I found a high-resolution picture of the IO board PCB in ‘as made’ representation on the OSH Park’s website. Neato. Front: Back: Read more…
2017-06-06
While waiting for the I/O board PCB to come back from fabrication I started designing the BBB cape that will house the serial drivers, power supply to the I/O board, more LEDs, and etc. This of course is necessary because the BBB’s serial ports operate at TTL level and are not tolerant of “proper” RS232 voltages and its I/O pins must not have voltage applied until the chip boots (the reset line goes high). First Read more…
2017-06-03
The board has been ordered, panelized, and sent off to production. So far the process has been moving along at a much faster clip than I anticipated. The board was panelized the same day I placed the order even though I ordered fairly late in the afternoon; certainly after business hours. The next day I received an email that the board has been sent off to fabrication. I know the email says that they expect Read more…
2017-05-31
The board circuit design and schematic are done. This is pretty terrible picture export. I couldn’t figure out how (spent 15 seconds) to export an SVG of the board without the copper fills. And here is the 3D rendering. A lot of 3D representations of components are missing, but the general gist is conveyed. All of the design work was done using KiCad (http://kicad-pcb.org/) EDA. Which of course means that I had to learn KiCad. Read more…
2017-05-06
Finally real progress is being made. The I2C communication stuff is working on both chips. I’m taking the register-based approach and have tested the implementation of all of the basic registers. Did a bit of stress testing on the communications stuff – weird input, input overflowing buffer sizes, collisions, and etc. and everything seems to be working fairly well in a sense that there’s no corruption, the failures are predictable and graceful, all data gets Read more…
2017-04-30
It has been a while since the last update and for good reasons. So after screwing around with the DAC on the BeagleBone I decided that I really didn’t like it. What’s with this 1.8 volt max nonsense? Now I’m no EE, so please forgive the laymen’s terminology. The BeagleBone has a 12 bit ADC on-board which means that it can split the supplied 1.8V (max) into 4096 discrete steps. Which works out (if my Read more…