{"id":160,"date":"2013-03-11T22:13:17","date_gmt":"2013-03-12T06:13:17","guid":{"rendered":"http:\/\/schminktronics.com\/blog\/?p=160"},"modified":"2013-03-27T14:39:17","modified_gmt":"2013-03-27T22:39:17","slug":"counter-test-2","status":"publish","type":"post","link":"http:\/\/schminktronics.com\/blog\/archives\/160","title":{"rendered":"Counter Test 2"},"content":{"rendered":"

Counter Test 2 works, but not quite right. For some reason, I have to set the prescaler on timer 2 to \/64. At first, that worked quite well and gave me exactly what I expected, but by the time I got the camera out, the lines were no longer at 3, 6, 9, and 12:<\/p>\n

\"Those<\/a>

Those lines should be at 3, 6, 9, 12 o’clock. Something’s not quite right…<\/p><\/div>\n

I suspect my problem here is that I should really be adjusting the prescalers on the fly instead of using the hardcoded values I designed in. My guess is that I’m overflowing what will fit into the 8 bit timer. I wish I could tell what I was writing in there. I may need to write the binary value again.<\/p>\n

The code I used for this is:<\/p>\n\n

1\n2\n3\n4\n5\n6\n7\n8\n9\n10\n11\n12\n13\n14\n15\n16\n17\n18\n19\n20\n21\n22\n23\n24\n25\n26\n27\n28\n29\n30\n31\n32\n33\n34\n35\n36\n37\n38\n39\n40\n41\n42\n43\n44\n45\n46\n47\n48\n49\n50\n51\n52\n53\n54\n55\n56\n57\n58\n59\n60\n61\n62\n63\n64\n65\n66\n67\n68\n69\n70\n71\n72\n73\n74\n75\n76\n77\n78\n79\n80\n81\n82\n83\n84\n85\n86\n87\n88\n89\n90\n91\n92\n93\n94\n95\n96\n97\n98\n99\n<\/pre><\/td>
\/\/ Using the spinner board to test 328 counters<\/span>\n \n#include <SPI.h><\/span>\n \nconst<\/span> int<\/span> HALL  =<\/span>  2<\/span>;<\/span> \/\/ PD2<\/span>\nconst<\/span> int<\/span> BLANK =<\/span>  8<\/span>;<\/span> \/\/ PB0<\/span>\nconst<\/span> int<\/span> LAT   =<\/span>  9<\/span>;<\/span> \/\/ PB1<\/span>\n \nconst<\/span> int<\/span> HALL_INT =<\/span> 0<\/span>;<\/span> \/\/ Hall effect interrupt 0 on PD2 (INT0)<\/span>\n \nunsigned<\/span> int<\/span> savedCounter =<\/span> 0<\/span>;<\/span>\nunsigned<\/span> int<\/span> slice =<\/span> 0<\/span>;<\/span>\n \nvoid<\/span> hallStart(<\/span>void<\/span>)<\/span> {<\/span>\n  \/\/ TCNT1 is counts per full revolution<\/span>\n  savedCounter =<\/span> TCNT1;<\/span>\n  TCNT1 =<\/span> 0<\/span>;<\/span>\n \n  \/\/ Also reset TCNt2 (slice counter) so we always start in a known<\/span>\n  \/\/ state<\/span>\n  TCNT2 =<\/span> 0<\/span>;<\/span>\n \n  \/\/ Calculate a new compare value for timer 2 based on how fast our last revolution was.<\/span>\n  \/\/ 512 angle slices, so divide the savedCounter by 512 to get the count per slice<\/span>\n  \/\/ But we also have a \/8 prescaler, so instead divide by 4096<\/span>\n  int<\/span> sliceCount =<\/span> savedCounter \/<\/span> 4096<\/span>;<\/span>\n \n  \/\/ Saved the new slice counter<\/span>\n  OCR2A =<\/span> sliceCount;<\/span>  \n \n  \/\/ Reset the slice number<\/span>\n  slice =<\/span> 0<\/span>;<\/span>\n \n  \/\/ Now start the 8 bit counter 2<\/span>\n  TCCR2B =<\/span> 6<\/span>;<\/span>                   \/\/ Set \/256 prescaler<\/span>\n}<\/span>\n \n\/\/ ISR for the timer to switch the LEDs<\/span>\nISR(<\/span>TIMER2_COMPA_vect)<\/span>\n{<\/span>\n  if<\/span> (<\/span>slice ==<\/span> 0<\/span> ||<\/span> slice ==<\/span> 128<\/span> ||<\/span> slice ==<\/span> 256<\/span> ||<\/span> slice ==<\/span> 384<\/span>)<\/span>\n  {<\/span>\n    setLeds(<\/span>0xFFFF<\/span>)<\/span>;<\/span>\n  }<\/span>\n  else<\/span> if<\/span> (<\/span>slice ==<\/span> 1<\/span> ||<\/span> slice ==<\/span> 129<\/span> ||<\/span> slice ==<\/span> 257<\/span> ||<\/span> slice ==<\/span> 385<\/span>)<\/span>\n  {<\/span>\n    setLeds(<\/span>0x0001<\/span>)<\/span>;<\/span>\n  }<\/span>\n \n  slice++;<\/span>\n}<\/span>\n \nvoid<\/span> setup(<\/span>)<\/span> {<\/span>\n  digitalWrite(<\/span>LAT,<\/span> LOW)<\/span>;<\/span>\n  pinMode(<\/span>LAT,<\/span> OUTPUT)<\/span>;<\/span>     \n \n  digitalWrite(<\/span>BLANK,<\/span> HIGH)<\/span>;<\/span>\n  pinMode(<\/span>BLANK,<\/span> OUTPUT)<\/span>;<\/span>     \n \n  pinMode(<\/span>HALL,<\/span> INPUT_PULLUP)<\/span>;<\/span>\n \n  \/\/ Setup the 16 bit counter counter 1<\/span>\n  TCCR1A =<\/span> 0<\/span>;<\/span>                   \/\/ Turn off output compare modes<\/span>\n  TCCR1B =<\/span> 2<\/span>;<\/span>                   \/\/ Turn on clk\/8 prescaler<\/span>\n \n  \/\/ Setup 8 bit counter 2<\/span>\n  TCCR2A =<\/span> 2<\/span>;<\/span>                   \/\/ CTC mode<\/span>\n  TCCR2B =<\/span> 0<\/span>;<\/span>                   \/\/ Start with timer off<\/span>\n  TIMSK2 =<\/span> 2<\/span>;<\/span>                   \/\/ Enable Output Compare A interrupt<\/span>\n \n  attachInterrupt(<\/span>HALL_INT,<\/span> hallStart,<\/span> FALLING)<\/span>;<\/span>\n \n  SPI.begin<\/span>(<\/span>)<\/span>;<\/span>\n  SPI.setDataMode<\/span>(<\/span>SPI_MODE0)<\/span>;<\/span>\n  SPI.setBitOrder<\/span>(<\/span>LSBFIRST)<\/span>;<\/span>\n  SPI.setClockDivider<\/span>(<\/span>SPI_CLOCK_DIV2)<\/span>;<\/span> \/\/ Datasheet says 35 MHz max, so 8 MHz is fine<\/span>\n \n  TCNT1 =<\/span> 0<\/span>;<\/span>\n}<\/span>\n \nvoid<\/span> setLeds(<\/span>unsigned<\/span> int<\/span> pattern)<\/span> {<\/span>\n  \/\/ Blank the LEDS<\/span>\n  digitalWrite(<\/span>BLANK,<\/span> HIGH)<\/span>;<\/span>\n \n  \/\/ Transfer the data<\/span>\n  SPI.transfer<\/span>(<\/span>pattern &<\/span> 0xFF<\/span>)<\/span>;<\/span>\n  SPI.transfer<\/span>(<\/span>pattern >><\/span> 8<\/span>)<\/span>;<\/span>\n \n  \/\/ Latch the data<\/span>\n  digitalWrite(<\/span>LAT,<\/span> HIGH)<\/span>;<\/span>\n  digitalWrite(<\/span>LAT,<\/span> LOW)<\/span>;<\/span>\n \n  \/\/ Unblank the LEDS<\/span>\n  digitalWrite(<\/span>BLANK,<\/span> LOW)<\/span>;<\/span>\n}<\/span>\n \nvoid<\/span> loop(<\/span>)<\/span> {<\/span>\n  \/\/ That's right--nothing to do here<\/span>\n}<\/span><\/pre><\/td><\/tr><\/table><\/div>\n\n
 <\/p>\n","protected":false},"excerpt":{"rendered":"
Counter Test 2 works, but not quite right. For some reason, I have to set the prescaler on timer 2 to \/64. At first, that worked quite well and gave me exactly what I expected, but by the time I … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-160","post","type-post","status-publish","format-standard","hentry","category-spinnerhd"],"_links":{"self":[{"href":"http:\/\/schminktronics.com\/blog\/wp-json\/wp\/v2\/posts\/160","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/schminktronics.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/schminktronics.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/schminktronics.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/schminktronics.com\/blog\/wp-json\/wp\/v2\/comments?post=160"}],"version-history":[{"count":4,"href":"http:\/\/schminktronics.com\/blog\/wp-json\/wp\/v2\/posts\/160\/revisions"}],"predecessor-version":[{"id":176,"href":"http:\/\/schminktronics.com\/blog\/wp-json\/wp\/v2\/posts\/160\/revisions\/176"}],"wp:attachment":[{"href":"http:\/\/schminktronics.com\/blog\/wp-json\/wp\/v2\/media?parent=160"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/schminktronics.com\/blog\/wp-json\/wp\/v2\/categories?post=160"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/schminktronics.com\/blog\/wp-json\/wp\/v2\/tags?post=160"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}