My first Arduino shield - Page 1
Forum section: electronics / projects

author: mikeblankenship
author_rank: Newbie
timestamp: November 07, 2015, 08:45:20 pm
content: Hello EEVblogites!!Im about 1 week away from sending my first Arduino UNO based shield design to be manufactured.I wanted to get a little input from the group.As you can see from the attachments the main sensor is a 16x4 pixel thermal imager (MLX90620/21)I have tested it on breadbard and the results are "ballpark" except for the 90621 which is ~10F off from the 90620Im working with the coder who converted someone else's code from a different libraryI have also thrown in an I2C bus buffer and the pullups (for an external are set for a 20M cable. I have created a quick and dirty VB.netbased application to parse and display the data. There is also a 1wire local and remote bus with an extension connector.Its a 4 layer board and 1 SDA and 1 SCL line do cross at layer 1 and layer 4, Im thinking that should not be a problembecause of the low speed ... at least I think so ....When Im complete I want to send to Dave so he can rip the design to schreds in the way only Dave can do!!Let me know your first impressions!mikey

author: sleemanj
author_rank: Super Contributor
timestamp: November 08, 2015, 04:26:15 am
content: Couple of observations.First you are using the UNOR3 pin layout (8+10+6+8) which has the extra (simply duplicated) I2C pins - you could use original UNO layout (8+8+6+6) just as well and then your shield could fit onto an original UNO or an R3 UNO.Do you really need 4 layers?

author: mikeblankenship
author_rank: Newbie
timestamp: November 08, 2015, 04:51:59 am
content: sleemanj,Thanks for pointing out the differences between the R1 and the R3, this would definitely make it more compatible.I really don't need 4 layers, it just made the layout easier for me, the gnd gonnections would not be so hard I could just tiethem to the plane. Ill look at some of Daves videos on youtube, and see if they show examples of creating a power bus.Thanks for your input.mike

author: homebrew
author_rank: Frequent Contributor
timestamp: November 08, 2015, 02:28:44 pm
content: No, you won't need 4 layers for that board. At least not, if you don't have any EMC concerns. Just flood fill TOP and BOTTOM with an ground pour and you should be happy. Use lots of GND-vias to stitch the planes together. If you have "vias unlimited" go full tilt and place a row of vias along the entire outer dimension.I2C for a 20m connections doesn't seem a good idea either. I2C is not intended as a field bus ...I would use RS485 in between the boards to cross that distance.

author: mikeblankenship
author_rank: Newbie
timestamp: November 09, 2015, 09:23:38 am
content: Ok, I made the changes :Now its Arduino R1-R3 compatible (Thanks sleemanj)4 layer to 2 layerRemoved the detailed info about the parts and just put the locator info.Im using ExpressPCB ... one of these days I need to learn Eagle or Kicad

author: lovemb
author_rank: Contributor
timestamp: November 09, 2015, 06:47:19 pm
content: Why do you have vias on Analog in 4+5 pins?

author: mikeblankenship
author_rank: Newbie
timestamp: November 09, 2015, 06:49:37 pm
content: A4 and A5 are SDA and SCL for I2C. The vias are used to route to the second layer