{"action":"created","issue":{"url":"https://api.github.com/repos/icebreaker-fpga/icebreaker/issues/14","repository_url":"https://api.github.com/repos/icebreaker-fpga/icebreaker","labels_url":"https://api.github.com/repos/icebreaker-fpga/icebreaker/issues/14/labels{/name}","comments_url":"https://api.github.com/repos/icebreaker-fpga/icebreaker/issues/14/comments","events_url":"https://api.github.com/repos/icebreaker-fpga/icebreaker/issues/14/events","html_url":"https://github.com/icebreaker-fpga/icebreaker/issues/14","id":358731205,"node_id":"MDU6SXNzdWUzNTg3MzEyMDU=","number":14,"title":"Explore the possibility of using a low cost STM32 instead of FTDI","user":{"login":"esden","id":17334,"node_id":"MDQ6VXNlcjE3MzM0","avatar_url":"https://avatars3.githubusercontent.com/u/17334?v=4","gravatar_id":"","url":"https://api.github.com/users/esden","html_url":"https://github.com/esden","followers_url":"https://api.github.com/users/esden/followers","following_url":"https://api.github.com/users/esden/following{/other_user}","gists_url":"https://api.github.com/users/esden/gists{/gist_id}","starred_url":"https://api.github.com/users/esden/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/esden/subscriptions","organizations_url":"https://api.github.com/users/esden/orgs","repos_url":"https://api.github.com/users/esden/repos","events_url":"https://api.github.com/users/esden/events{/privacy}","received_events_url":"https://api.github.com/users/esden/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":{"url":"https://api.github.com/repos/icebreaker-fpga/icebreaker/milestones/3","html_url":"https://github.com/icebreaker-fpga/icebreaker/milestone/3","labels_url":"https://api.github.com/repos/icebreaker-fpga/icebreaker/milestones/3/labels","id":3797762,"node_id":"MDk6TWlsZXN0b25lMzc5Nzc2Mg==","number":3,"title":"V2.0a","description":null,"creator":{"login":"esden","id":17334,"node_id":"MDQ6VXNlcjE3MzM0","avatar_url":"https://avatars3.githubusercontent.com/u/17334?v=4","gravatar_id":"","url":"https://api.github.com/users/esden","html_url":"https://github.com/esden","followers_url":"https://api.github.com/users/esden/followers","following_url":"https://api.github.com/users/esden/following{/other_user}","gists_url":"https://api.github.com/users/esden/gists{/gist_id}","starred_url":"https://api.github.com/users/esden/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/esden/subscriptions","organizations_url":"https://api.github.com/users/esden/orgs","repos_url":"https://api.github.com/users/esden/repos","events_url":"https://api.github.com/users/esden/events{/privacy}","received_events_url":"https://api.github.com/users/esden/received_events","type":"User","site_admin":false},"open_issues":2,"closed_issues":0,"state":"open","created_at":"2018-11-05T18:54:39Z","updated_at":"2018-11-05T19:00:52Z","due_on":null,"closed_at":null},"comments":12,"created_at":"2018-09-10T18:01:35Z","updated_at":"2018-11-08T19:49:48Z","closed_at":null,"author_association":"MEMBER","body":"There are very low cost STM32 that don't even require an external oscillator to be used with USB.\r\n\r\n[STM32F042K6T6](https://www.st.com/en/microcontrollers/stm32f042k6.html) for example can be purchased on aliexpress for a really good price. I have also compared prices of similar parts from other vendors. The STM32 turns out to be lower cost than any alternative chip with this kind of specifications. With added bonus of being easily available from a lot of vendors on aliexpress.\r\n\r\nList of advantages of the STM32:\r\n* significantly lower cost: ~$15 lower retail cost of the icebreaker\r\n* less parts and placements: no external flash chip and no external oscillator needed\r\n* automatic unique serial number in the descriptor strings generated from the unique id of the STM32. No need to track unique serial numbers in manufacturing.\r\n* flexible firmware on the STM32 alowing for updates and new features in the future\r\n* Possible to wire up so that we don't need to use any jumpers to choose FLASH or FPGA flashing\r\n\r\nList of disadvantages of the STM32:\r\n* Need to develop firmware for the STM32\r\n* Need to develop desktop program for flashing (multiplatform software developemnt)\r\n* Mess with drivers depending on which model we use (windows headaches mostly)\r\n* No high speed USB just full speed.\r\n* No optional asynchronous FIFO mode.\r\n\r\nList of things we retain:\r\n* Ability to flash the on board FLASH chip\r\n* Ability to upload bitstream to the FPGA directly\r\n* Ability to connect to the UART serial port (USB to serial converter)\r\n* Generate 12MHz external clock for the FPGA (STM32 MCO pin)\r\n\r\nAlternatives to the STM32:\r\n* [EFM32HG309](https://www.silabs.com/documents/public/data-sheets/efm32hg-datasheet.pdf) (same chip as on the [Tomu board](https://tomu.im/))\r\n* [PIC16F1455](https://www.microchip.com/wwwproducts/en/PIC16F1455) (same chip as on the [TinyFPGA-A-Prog](https://github.com/tinyfpga/TinyFPGA-A-Programmer))\r\n* [ATSAMD21E15B-MU](https://www.microchip.com/wwwproducts/en/ATSAMD21E15) (same chip as on the [FPGAHelper](https://hackaday.io/project/160254-fpga-helper))\r\n\r\nThis issue is here to track the testing of that part. Close it if we decide not to go down that path, or we realize that it has some big flaw that is worth the 4x price difference of the FTDI chip. Or when we decide to use this approach and decide that this is our main path.\r\n"},"comment":{"url":"https://api.github.com/repos/icebreaker-fpga/icebreaker/issues/comments/437132480","html_url":"https://github.com/icebreaker-fpga/icebreaker/issues/14#issuecomment-437132480","issue_url":"https://api.github.com/repos/icebreaker-fpga/icebreaker/issues/14","id":437132480,"node_id":"MDEyOklzc3VlQ29tbWVudDQzNzEzMjQ4MA==","user":{"login":"esden","id":17334,"node_id":"MDQ6VXNlcjE3MzM0","avatar_url":"https://avatars3.githubusercontent.com/u/17334?v=4","gravatar_id":"","url":"https://api.github.com/users/esden","html_url":"https://github.com/esden","followers_url":"https://api.github.com/users/esden/followers","following_url":"https://api.github.com/users/esden/following{/other_user}","gists_url":"https://api.github.com/users/esden/gists{/gist_id}","starred_url":"https://api.github.com/users/esden/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/esden/subscriptions","organizations_url":"https://api.github.com/users/esden/orgs","repos_url":"https://api.github.com/users/esden/repos","events_url":"https://api.github.com/users/esden/events{/privacy}","received_events_url":"https://api.github.com/users/esden/received_events","type":"User","site_admin":false},"created_at":"2018-11-08T19:49:48Z","updated_at":"2018-11-08T19:49:48Z","author_association":"MEMBER","body":"@osterwood are you sure they have USB HS? From the datasheets it seems they only have a FullSpeed transceiver built in. But I might be missing something. There are plenty of ARM Cortex chips that have HighSpeed support but require an external PHY. I was hoping to avoid that."}}
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