{"action":"closed","issue":{"url":"https://api.github.com/repos/roybaer/sduino_uno/issues/1","repository_url":"https://api.github.com/repos/roybaer/sduino_uno","labels_url":"https://api.github.com/repos/roybaer/sduino_uno/issues/1/labels{/name}","comments_url":"https://api.github.com/repos/roybaer/sduino_uno/issues/1/comments","events_url":"https://api.github.com/repos/roybaer/sduino_uno/issues/1/events","html_url":"https://github.com/roybaer/sduino_uno/issues/1","id":263677823,"node_id":"MDU6SXNzdWUyNjM2Nzc4MjM=","number":1,"title":"comments on the schematic and PCB","user":{"login":"tenbaht","id":16648613,"node_id":"MDQ6VXNlcjE2NjQ4NjEz","avatar_url":"https://avatars1.githubusercontent.com/u/16648613?v=4","gravatar_id":"","url":"https://api.github.com/users/tenbaht","html_url":"https://github.com/tenbaht","followers_url":"https://api.github.com/users/tenbaht/followers","following_url":"https://api.github.com/users/tenbaht/following{/other_user}","gists_url":"https://api.github.com/users/tenbaht/gists{/gist_id}","starred_url":"https://api.github.com/users/tenbaht/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/tenbaht/subscriptions","organizations_url":"https://api.github.com/users/tenbaht/orgs","repos_url":"https://api.github.com/users/tenbaht/repos","events_url":"https://api.github.com/users/tenbaht/events{/privacy}","received_events_url":"https://api.github.com/users/tenbaht/received_events","type":"User","site_admin":false},"labels":[{"id":712630303,"node_id":"MDU6TGFiZWw3MTI2MzAzMDM=","url":"https://api.github.com/repos/roybaer/sduino_uno/labels/bug","name":"bug","color":"ee0701","default":true},{"id":712630305,"node_id":"MDU6TGFiZWw3MTI2MzAzMDU=","url":"https://api.github.com/repos/roybaer/sduino_uno/labels/enhancement","name":"enhancement","color":"84b6eb","default":true}],"state":"closed","locked":false,"assignee":{"login":"roybaer","id":7901580,"node_id":"MDQ6VXNlcjc5MDE1ODA=","avatar_url":"https://avatars2.githubusercontent.com/u/7901580?v=4","gravatar_id":"","url":"https://api.github.com/users/roybaer","html_url":"https://github.com/roybaer","followers_url":"https://api.github.com/users/roybaer/followers","following_url":"https://api.github.com/users/roybaer/following{/other_user}","gists_url":"https://api.github.com/users/roybaer/gists{/gist_id}","starred_url":"https://api.github.com/users/roybaer/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/roybaer/subscriptions","organizations_url":"https://api.github.com/users/roybaer/orgs","repos_url":"https://api.github.com/users/roybaer/repos","events_url":"https://api.github.com/users/roybaer/events{/privacy}","received_events_url":"https://api.github.com/users/roybaer/received_events","type":"User","site_admin":false},"assignees":[{"login":"roybaer","id":7901580,"node_id":"MDQ6VXNlcjc5MDE1ODA=","avatar_url":"https://avatars2.githubusercontent.com/u/7901580?v=4","gravatar_id":"","url":"https://api.github.com/users/roybaer","html_url":"https://github.com/roybaer","followers_url":"https://api.github.com/users/roybaer/followers","following_url":"https://api.github.com/users/roybaer/following{/other_user}","gists_url":"https://api.github.com/users/roybaer/gists{/gist_id}","starred_url":"https://api.github.com/users/roybaer/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/roybaer/subscriptions","organizations_url":"https://api.github.com/users/roybaer/orgs","repos_url":"https://api.github.com/users/roybaer/repos","events_url":"https://api.github.com/users/roybaer/events{/privacy}","received_events_url":"https://api.github.com/users/roybaer/received_events","type":"User","site_admin":false}],"milestone":null,"comments":3,"created_at":"2017-10-07T22:55:08Z","updated_at":"2018-08-04T10:36:24Z","closed_at":"2018-08-04T10:36:24Z","author_association":"NONE","body":"This looks amazing! I am looking forward to see the first prototypes!\r\n\r\nLooking at the schematic I would like to comment on the hardware:\r\n- to initially program a serial bootloader it would be very handy to have a ST-Link compatible 4-pin SWIM connector. I suggest using the same pinout as used for the stm8sblue PCB: RST, GND, SWIM, MCUVCC\r\n- The serial connection between the CH340 and the CPU looks weired to me. Really through the LEDs? Maybe the pins RN2-2 and RN2-3 are supposed to connect to MCUVCC and the IO0/RX and IO1/TX labels should be connected to RN3-7 and RN3-8?\r\n- it might be useful to be able to open the connection between CH340/TXD and STM8/RxD in case the pin is used as an output pin. Solderbridge? Jumper?\r\n- Does J2 really connects to RESET two times? Maybe RESET and GND?\r\n- I am not sure if Q1 is always guaranteed to connect USBVCC to +5V if UIN is not present. U5 is not powered before Q1 is active, but Q1 can't be active before U5A outputs a valid signal. Possible deadlock? Maybe use the unused resistor RN1/3-6 to pull Q1/G to GND?\r\n\r\nIf you are planning to develop this design further into a commercial product it might be worth to:\r\n- add decoupling filters to VBUS and DC to reduce EM emissions (ferrite beards 220r@100MHz and 1nF+100nF capacitors)\r\n- additional ESD protection on the USB port might be useful\r\n\r\ngeneral:\r\n\r\n- for people not familiar with kicad it might be convenient to add the schematic as pdf to the repository\r\n\r\nPCB:\r\n- a GND guard ring from pin 4 around Y2 and the clock signals would help **a lot** with the EM values.\r\n- the via for SCL under Y2 might connect to the crystal housing after assembly\r\n- SDA is a very sensible signal, but it is routed right under Y2, even on the top side. Might cause malfunctions in I2C communication later.\r\n- rearrage C1, C2 and Y1 is in [Atmel application note AVR186](http://www.atmel.com/Images/Atmel-8128-Best-Practices-for-the-PCB-Layout-of-Oscillators_ApplicationNote_AVR186.pdf)\r\n\r\nIMHO it would be worth the effort to move Y2 closer to the CPU and get the I2C signals out of the way. It might help to use a smaller cyrstal. E.g. the [FA-238 series in size 3225](https://www.digikey.com/product-detail/en/epson/FA-238-16.0000MB-C3/SER3686TR-ND/2403378). The price difference to a HC49-type is only a few cents. Resonators with integrated capacitors are another option, e.g. [AVX PRQC series](https://www.digikey.com/product-detail/en/avx-corp-kyocera-corp/PRQC16.00CR5010X000/1253-1675-1-ND/5870331) or [Abracon AWSCR series](https://www.digikey.com/product-detail/en/abracon-llc/AWSCR-16.00CV-T/535-10008-1-ND/2001631)\r\n"}}
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