Author: jtamayo

This week we did not get that much done, we met on Monday and then Wednesday had our Ethics meeting.

I largely looked at possible revisions for our PCB and looked for potential boardhouses to order from, but it would be best to have a fully working breadboard prototype before we order the PCB. Our Diodes arrived on Friday so that should be done some time next week.

Besides that, Carlo’s wrote an email and we reached out to CLASS, the organization that could potentially put us in contact with someone with Cerebral Palsy, but they have not responded.

We should get back on track next week, but we shouldn’t imagine that we have too much time and get over-confident. In truth we only have a few weeks to integrate and it may be tight due to delays.

• Jorge’s Status Report for 3/18/22

This week we tested the software and made sure it worked well enough with a prototype of the board. We put in an order for the Diode’s we will need and with those we will know finally whether absolutely everything is working as intended. But as mentioned in the group report, the behavior is about what we expected. (The software works fine but once we do inputs from separate columns ghosting becomes an issue.)

Besides that it was my time to start work on the PCB layout. We ran into a slight delay which I made up by working on the layout on Friday. The Eagle license we had was only the free one and our Board dimensions were beyond the allowed limit. I had to submit some enrollment documentation, transcripts, and an ID but we ended up getting the Eagle education (through Fusion 360) license approved the next day.

 

Here below is the PCB:

Notes about the board:

• It has no ground plane, this is unnecessary because we would only need a ground plane for the LEDs in the switches, which we are not using
• I am slightly worried about the space the Diodes (not the LEDs) take up, but if they take up space for our switches we can just solder them on the back of the board so I don’t see that as being a big problem.
•  The pin headers that interface the Pi are organized as rows and columns, it keeps the board neat and orderly. Rows flow through the bottom of the board, columns through the top. Both eventually rout to the top to their respective Pi interfaces
• LED pins are left disconnected for now, if we decide to use them for some reason I can add some wires and resistors to make use of them, but it isn’t high priority.
• Spacing is made with 20mm keycaps in mind, and a key-guard. Hopefully the dimensions wont be too ridiculous but there is room to make changes next week before we order the board.

My main worry right now is the time frame, we may need to pay for express shipping so we can get the board on schedule.

 

• Jorge’s Status Report for 2/26/22

This week I worked on the design review Report with the team, I presented our design review slides on Monday, and made modifications to the schematic. The changes to the schematic are the following:

I added new header pins which we plan to solder some male connectors to, this is for the interface we are making from the keyboard to the pi

Included a Frame for the schematic, mainly aesthetic

Rerouted some wires in consideration of the software. By including four new rows for the specific combination keys, it will help make our software simpler to implement.

These are the final steps before getting started with the actual pcb layout. This part shouldn’t be too hard but I expect changes to be made based on the feedback from the professor in HCI. I am very familiar with the PCB layout portion of Eagle and don’t feel its necessary to layout an entire board ill probably have to change, so I will wait until after our meeting and then proceed making the PCB.

In the mean time, I can get started on designing a little layout for our planned de-activating toggle switches and make a schematic, but that part should be easier to do than the main Keyboard PCB.

• Jorge’s Status Report for 2/19/22

This week we worked on the design review presentation, while also working on our project so we had some more solid metrics for the presentation itself.

We created a preliminary Survey together, with two different texts, each with a different level of difficulty, which people who test our keyboard will be asked to type. From these texts we will measure the errors through either software or visible observation. Beyond that, the survey also has some questions regarding the comfort of the device and some other metrics. This will hopefully give us more solid ground for our testing process.

In terms of work outside of the design review. I started working on the Eagle Schematic for the layout of our board.  The PCB itself however, will likely change once we get feedback on the design review and after. This along with some of the other things my teammates have done means that we are actually somewhat ahead of schedule, but in truth this is necessary since some of our work is subject to revision once we get feedback from the Professor in HCI who specializes on accessibility.

 

Above is the circuit schematic. Generally the layout is solid, but the special characters like Alt, Ctrl and Shift are likely to change to allow us to make the software simpler. Besides that, all thats left is a component so that when we go to make the board layout we have some location for male connector pins.

As stated before, we are somewhat ahead of schedule when it comes to some concrete work, but that basically means we are on schedule, since our chance to speak with a professor in HCI was only available after the design review.

 

• Jorge’s Status Report for 2/12/22

I started by designing some preliminary layouts for our keyboard which is designed for right handed use for now, but can be easily flipped if necessary. I based it off of existing layouts but with a goal to make a much simpler to use and intuitive layout. Besides the design of the keyboard button layout we also looked at the components we will be using. Standard mechanical keyboard switches work well and can be laid out in Eagle relatively easily.  We decided on linear key switches because they are the most comfortable to use and Carlos will be designing some custom keycaps for them that will be slightly bigger than standard.

For the board itself we will use a matrix scanning design to get the most use out of our IO pins on the Pi. Currently with only 26 GPIO pins it may be difficult to get 40+ keys to work but that becomes a non-issue when using matrix scanning. With Matrix scanning for every ‘n’ pins we get ((n^2)/4) possible input combinations which means we have more than enough input.