{"id":167,"date":"2023-11-24T12:44:59","date_gmt":"2023-11-24T12:44:59","guid":{"rendered":"http:\/\/karlsblog.bigmight.com\/blog\/?p=167"},"modified":"2023-11-25T13:54:46","modified_gmt":"2023-11-25T13:54:46","slug":"high-precision-frequency-counter-using-gps-part2","status":"publish","type":"post","link":"https:\/\/karlsblog.bigmight.com\/blog\/2023\/11\/24\/high-precision-frequency-counter-using-gps-part2\/","title":{"rendered":"High Precision Frequency Counter using GPS (Part2)"},"content":{"rendered":"\n

Following from previous posting<\/a> I have connected a STM32F429i-DISC1 board to us UBLOX NEO-6M GPS module (see https:\/\/www.ebay.co.uk\/itm\/313603433572<\/a>) and programmed a 32 bit counter in capture compare mode running at 80MHz.<\/p>\n\n\n\n

\"STD32f429i-Disc1<\/a>
NEO-6M GPS with PPS triggering counter<\/figcaption><\/figure>\n\n\n\n

After the GPS settled I recorded a number of counts varying by +-200 using the inbuilt 8MHz crystal.<\/p>\n\n\n\n

This is far too much jitter, at present i t is uncertain if the reason is<\/p>\n\n\n\n

  1. Crystal frequency variation due to quality of crystal<\/li>
  2. Crystal frequency variation due to supply voltage<\/li>
  3. STM32 PLL stability.<\/li><\/ol>\n\n\n\n

    I will first attempt to attach a better crystal. The STM32F429 accepts an external input from 4MHz to 26MHz. From RS components I considered a 24Mhz TCXO https:\/\/uk.rs-online.com\/web\/p\/tcxo-oscillators\/2499379<\/a> but I only wanted one, so ended up buying o e of these from ebay https:\/\/www.iqdfrequencyproducts.com\/products\/pn\/LFTCXO075797Reel.pdf<\/a>.<\/p>\n\n\n\n

    I’ll update on stability when it arrives.<\/p>\n\n\n\n

    I will provide the eclipse project for the board firmware. It includes UI, GPS serial communications and timer programming. All running under FreeRTOS.<\/p>\n","protected":false},"excerpt":{"rendered":"

    Following from previous posting I have connected a STM32F429i-DISC1 board to us UBLOX NEO-6M GPS module (see https:\/\/www.ebay.co.uk\/itm\/313603433572) and programmed a 32 bit counter in capture compare mode running at 80MHz. After the GPS settled I recorded a number of counts varying by +-200 using the inbuilt 8MHz crystal. This is far too much jitter, … Continue reading “High Precision Frequency Counter using GPS (Part2)”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/karlsblog.bigmight.com\/blog\/wp-json\/wp\/v2\/posts\/167"}],"collection":[{"href":"https:\/\/karlsblog.bigmight.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karlsblog.bigmight.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karlsblog.bigmight.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karlsblog.bigmight.com\/blog\/wp-json\/wp\/v2\/comments?post=167"}],"version-history":[{"count":8,"href":"https:\/\/karlsblog.bigmight.com\/blog\/wp-json\/wp\/v2\/posts\/167\/revisions"}],"predecessor-version":[{"id":181,"href":"https:\/\/karlsblog.bigmight.com\/blog\/wp-json\/wp\/v2\/posts\/167\/revisions\/181"}],"wp:attachment":[{"href":"https:\/\/karlsblog.bigmight.com\/blog\/wp-json\/wp\/v2\/media?parent=167"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karlsblog.bigmight.com\/blog\/wp-json\/wp\/v2\/categories?post=167"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karlsblog.bigmight.com\/blog\/wp-json\/wp\/v2\/tags?post=167"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}