Help hacking a laser tape measure?

N_Cook · 2019-08-05T15:56:09+00:00

Firstly for anyone else playing with these neat cheap laser diode measuring devices. I'm initially playing with a (Lidl) Parkside PLEM 50 (50m range), to eventually use a Lomvum LV 120 (120m range) coupled to a pc via Pi/Arduino. Both have 4 line 7segment LCD plus annunciators display with a "chip on glass" look-up page chip for decoding and driving the LCD. Made by and ident YGFB178004-A1 on the .5mm spacing ribbon and I know by swapping between each, they are compatible between both devices , completely different external and internal appearance, but same STM micro. 14 way ribbon to LCD , 2 w for backlight, 2w for power to chip on glass and a number of apparently inactive lines in measurement mode anyway . So d0 clock , d3 and d4 used for SPI update principal lastline of LCD and d2 +d3 active during power-up/first page but not in measure mode. Breaking-out at the ZIF ribbon socket and using Hobbycomponents "matchbox" pulse analyser and Sigrok/Pulseview and pairs of readings on the lower line of the LCD, ie switch unit on, then just pressing "measure" once initiates the SPI clock pulses. The LCD is updated from switch-on display in 0.5 to 1 seconds , so the data must be contained within the first 2 or 3 frames of data. Short duration bursts of clock then various amounts of dead space , as much as 400mS between frames, highly variable duration. I was hoping the same as , on link on seeing 17 4 bit words per frame (mainly, sometimes 13, sometimes 16) The first frame seems to have only 4 variants and is re-used for totally different last-line readings. Whatever I set sampling speed, clock polarity or phase etc I cannot avoid the "smearing" between frames ,eg 348-384 : 05 378-403 : 00 403-428 : 04 429-1961499 : 0C 980976-981002 : 0D 981001-981026 : 00 981026-981051 : 04 how to tidy up word apportionment ?. And then for pairs of metre/mm distance readings I cannot get any sense of pertinent words to decode/look-up (redundant 0's removed here for...

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N_Cook 5 years ago

Interesting info , I've downloaded for later . Just got back to this tide-gauge project, the optics part of it anyway. The bored hole through the lens has to be offset from centre by the half-inch of the separation of the laser output port and the centre of the large lens. Also covering over the small inset lens, so as not to confuse the range setting procedure. Some stainless steel "reusable drinks straws" I found for guiding the laser thru the lens without side-scatter being returned to the receiving lens. Just trying out a pan of water , shrouded against false returns, to check out over 20 metres initially. For real over tidal water comes later.

Global sea level rise to 2100 from curve-fitted existing altimetry data

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N_Cook 5 years ago

I'm way off trying to use this SPI coding , and I'm no codesmith , but for anyone else landing here, there may be an error in the

7segment/decimal conversion block

else if(c == 0x3F) decimal[i] = '0'; else if (c == 0x06) decimal[i] = '1'; else if (c == 0x6D) decimal[i] = '2'; else if (c == 0x4F) decimal[i] = '3'; else if (c == 0x56) decimal[i] = '4'; else if (c == 0x5B) decimal[i] = '5'; else if (c == 0x7B) decimal[i] = '6'; else if (c == 0x0E) decimal[i] = '7'; else if (c == 0x7F) decimal[i] = '8'; else if (c == 0x5F) decimal[i] = '9';

The hex 6D and 5B may need swapping around for the '2' and '5'

Global sea level rise to 2100 from curve-fitted existing altimetry data

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bronek 4 years ago

responding to

formatting link

, bronek wrote: int get_segment(int SegmentNo) // return 1if LCD segment SegmentNo is ON { int group,byte,bit; group = SegmentNo / 80; byte = (SegmentNo / 8) % 10; bit = SegmentNo % 8; uint8_t Bit = (1 << bit); uint8_t c = raw_segment_data[group * 10 + byte]; if(c & Bit) return 1; return 0;

} uint8_t raw_segment_data[40]; void analyze_data(void) // analyze 71bytes laser_buffer[71] { uint8_t data[6]; uint8_t decimal[8]; uint8_t buffer[32]; float distance = 0; long int distance_mm = 0; static long int last_distance_mm = 0; uint8_t c; int i; // remove LCD_commands, only use LCD data for(i = 0; i < 10;i++) raw_segment_data[i + 0] = laser_buffer[22+i]; for(i = 0; i < 10;i++) raw_segment_data[i + 10] = laser_buffer[35+i]; for(i = 0; i < 10;i++) raw_segment_data[i + 20] = laser_buffer[48+i]; for(i = 0; i < 10;i++) raw_segment_data[i + 30] = laser_buffer[61+i]; memset(data,0,6); // sign minus have SegmenNo 59, I do not use it if(get_segment(300)) data[0] |= 0x02 | 0x04; if(get_segment(61)) data[1] |= 0x01; if(get_segment(141)) data[1] |= 0x02; if(get_segment(221)) data[1] |= 0x04; if(get_segment(301)) data[1] |= 0x08; if(get_segment(220)) data[1] |= 0x10; if(get_segment(60)) data[1] |= 0x20; if(get_segment(140)) data[1] |= 0x40;

for(i = 0; i < 6; i++) { c = data[i]; if(c == 0x00) decimal[i] = '0'; // Prazdne uvodne miesta else if(c == 0x3F) decimal[i] = '0'; else if (c == 0x06) decimal[i] = '1'; else if (c == 0x6D) decimal[i] = '2'; else if (c == 0x4F) decimal[i] = '3'; else if (c == 0x56) decimal[i] = '4'; else if (c == 0x5B) decimal[i] = '5'; else if (c == 0x7B) decimal[i] = '6'; else if (c == 0x0E) decimal[i] = '7'; else if (c == 0x7F) decimal[i] = '8'; else if (c == 0x5F) decimal[i] = '9'; else decimal[i] = 'X'; } decimal[6] = 0; distance_mm = atol((char*)decimal); if(distance_mm == last_distance_mm) return; last_distance_mm = distance_mm; if(!distance_mm) return; distance = (float)(distance_mm) / 1000; if(get_segment(54) && get_segment(134))// metre i = sprintf((char*)buffer, "%.3f[m]\n\r",distance); if(get_segment(294)) // ft i = sprintf((char*)buffer, "%.3f[m]\n\r",distance * 0.3048); // if(get_segment(214) && get_segment(134)) // inch //i = sprintf((char*)buffer, "Zmen inch na m\n\r"); usart_print(buffer,i); }

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