{"id":2895,"date":"2024-10-22T16:57:52","date_gmt":"2024-10-22T15:57:52","guid":{"rendered":"https:\/\/www.robertprice.co.uk\/robblog\/?p=2895"},"modified":"2024-10-22T17:02:50","modified_gmt":"2024-10-22T16:02:50","slug":"rc2024-part-10-building-and-testing-the-updated-pcb","status":"publish","type":"post","link":"https:\/\/www.robertprice.co.uk\/robblog\/rc2024-part-10-building-and-testing-the-updated-pcb\/","title":{"rendered":"RC2024 \u2013 Part 11 \u2013 Building And Testing The Updated PCB"},"content":{"rendered":"\n

The new version of my Rotary Encoder Module PCB arrived yesterday. I couldn’t wait to solder it up.<\/p>\n\n\n\n

There were only a few small changes to the first PCB. I covered these when I wrote about building and testing the first PCB<\/a>.<\/p>\n\n\n\n

\"The<\/a><\/figure>\n\n\n\n

The biggest change I wanted to make was to introduce a sensible spoke size to the ground plane. Imagine my disappointment when I still struggled to solder to ground. I went back and looked at my design. The ground plane spoke sizes looked sensible at 0.25mm. Then I realised what I had done. I had placed a ground plane on both the front and back of the PCB. I never changed the spoke sizes on the back. This meant as I was soldering the heat was being wicked away in the large copper ground plane.<\/p>\n\n\n\n

I did eventually complete the PCB, and this time I used blue switches for the address port select and for the LEDs. This helps me tell the two different versions of the boards apart.<\/p>\n\n\n\n

Plugging it in and running my tests, I was happy to see everything still worked.<\/p>\n\n\n\n

Ports<\/h2>\n\n\n\n

Reading Shelia Dixon’s update on her RetroChallenge for the RC2014<\/a>, I saw she was using the same port as me.<\/p>\n\n\n\n

She mentioned she had spoken to Spencer Owen about the best port to use. I have followed her example and reached out to Spencer<\/a>. He has kindly reserved port D7 for rotary encoders on the RC2014. There is also A7 as a reserve port in case of clashes. This port can be used by other rotary encoder modules in the future, not just mine.<\/p>\n\n\n\n

One thing Spencer mentioned was about making it simpler to set an address port on the board. Rather than having 8 switches that allow any 8 bit port address to be used, a simple jumper to allow either D7 or A7 could be used.<\/p>\n\n\n\n

I have taken this on board and decided to design two more versions of the PCB.<\/p>\n\n\n\n

The first is essentially the same as my existing board, but with a single ground plane to the rear of the PCB. This also has smaller spoke sizes for ground so should be easier to solder.<\/p>\n\n\n\n

The second is a version without the full 8 bit port select switch. Instead I now have a single jumper to allow either D7 or A7 to be selected.<\/p>\n\n\n\n

This is what the binary forms of D7 and A7 look like. They are the same apart from bits A4, A5, and A6.<\/p>\n\n\n\n

D7 1101 0111
A7 1010 0111<\/p>\n\n\n\n

To allow the switching bits A6, A5, and A4 must be inverted when the jumper is swapped. I can just connect the jumper to either GND or +5V, that will allow A6 and A4 to swap, but A5 must always be the inverse of them. This will need to use an inverter.<\/p>\n\n\n\n

Rather than adding an extra chip to invert a single value, I decided I could swap the 74HCT32 OR chip to a 74HCT02 NOR gate. I was only using one of the existing OR gates, so swapping that over to a NOR, then running that through another joined NOR gate will give me the same result. I can also use one of the spare gates as an inverter for A5.<\/p>\n\n\n\n

When no rotary encoder is connected<\/h2>\n\n\n\n

At present, when no rotary encoder to port 1 or 2, the output for the Schmitt Trigger is high. When a rotary encoder is present it is low. This could cause a false reading as I check for high in my code.<\/p>\n\n\n\n

To solve this, I have added a pull up resistor array between the rotary encoder pins and the Schmitt Trigger. This is 100k resistor connected to +5v.<\/p>\n\n\n\n

To test this works I added a 100k resistor array to a breadboard and connected it between the PCB and Rotary Encoder. When the encoder was present it worked as expected. When I removed the encoder, it also worked.<\/p>\n\n\n\n

I have added this array to both of the new PCBs.<\/p>\n\n\n\n

The final change was to remove the ground hook from the top right of the board. This was only for testing and ground is available on the debug port anyway.<\/p>\n\n\n\n

Will the new PCBs arrive in time<\/h2>\n\n\n\n

There are only 9 days left before the official end of the 2024 RetroChallenge. I have ordered the new PCBs from JLCPCB, but I don’t know if they will arrive in time. I have also had to order some NOR gates from AliExpress, so that will also be over a week to arrive.<\/p>\n\n\n\n

Will they arrive before the end of the challenge? I hope so!<\/p>\n\n\n\n

The existing PCBs work, I just know they could be better.<\/p>\n","protected":false},"excerpt":{"rendered":"

The new version of my Rotary Encoder Module PCB arrived yesterday. I couldn’t wait to solder it up. There were only a few small changes to the first PCB. I covered these when I wrote about building and testing the first PCB. The biggest change I wanted to make was to introduce a sensible spoke … Continue reading “RC2024 \u2013 Part 11 \u2013 Building And Testing The Updated PCB”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":2897,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[113],"tags":[139,117,115,131],"class_list":["post-2895","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-rc2024","tag-pcb","tag-rc2014","tag-rc2024","tag-rotary-encoder"],"yoast_head":"\nRC2024 \u2013 Part 11 \u2013 Building And Testing The Updated PCB - Robert Price<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.robertprice.co.uk\/robblog\/rc2024-part-10-building-and-testing-the-updated-pcb\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"RC2024 \u2013 Part 11 \u2013 Building And Testing The Updated PCB - Robert Price\" \/>\n<meta property=\"og:description\" content=\"The new version of my Rotary Encoder Module PCB arrived yesterday. 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