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Forum Index : Microcontroller and PC projects : Cannot read Word variable using Webmite I2C
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| Johnfd Newbie  Joined: 04/08/2023 Location: AustraliaPosts: 6 |
G'day all, I'm really having troubles reading the I2C with a INA226. Software Webmite V6.1. The results for reading the word and current registers are only seeing the high byte. I've set config and calibration registers OK. To read a result register for voltage and current it is first necessary to write to the register to preparation for a read. e.g. I2C WRITE &H40,&H00,&H01,&H02 'set up register $H02 ready for volts read Next read the register I2C Read &H40,&H00,&H01,VoltOut Using in volts float or integer same result-an integer 0 to 42 (highest voltage available 0-14V). Similar with Current register. I've tried I2C Read &H40,&H00,&H02,VoltOut Same result. Similarly with the current register (I have config and calibration set). So the issue is I can't load a word variable from the INA226, only a single byte can be brought in. I know I must be doing something stupid but I've nearly worn out the keys on the computer. Here are my two routinge: SUB GetINA226SetupLoad SETPIN 21,22,I2C 'set the pins for I2C I2C OPEN 100,200 'speed in Hz, timeout in ms ' Get load volts ' register 01 shunt voltage, 02 is the bus voltage. ' register 04 is current register PAUSE 20 'give ana226 time I2C WRITE &H40,&H00,&H01,&H02 'set up register $H02 ready for read of volts I2C Read &H40,&H00,&H01,VoltOut 'read the volts voltout = voltout* 0.33333 + 0.005 'adjust the voltage and round Tempst$ = format$(VoltOut,"%.3f") 'get the volts in string form voltsL$ = left$(TempSt$,4) 'ready for elsewhere in the program PAUSE 20 'now to read the load current I2C WRITE &H40,&H00,&H01,&H04 'set up ready for read of current I2C Read &H40,&H00,&H01,AmpOut 'get the current after calibration has been set Tempst$ = format$(Ampout,"%.3f") 'format the current AmpsL$ = left$(TempSt$,4) print "Load: "voltsL$,"V ",Ampsl$,"A " 'Print volts/amps on Tera Term I2C CLOSE 'close the connection END SUB I'd really appreciate help with this. Thanks John |
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| Volhout Guru  Joined: 05/03/2018 Location: NetherlandsPosts: 5563 |
Hi John, Reading and writing I2C is always byte oriented. If you need to read a 16 bit value, you need to read 2x a byte register, and combine the 2 bytes to a single 16 bit. I do not own a INA226, bit it should be done this way DIM dta%(1) 'to hold the 2 bytes I2C WRITE &H40,&H00,&H01,&H02 'set up register $H02 ready for read of volts I2C Read &H40,&H00,&H02,dta%() 'read 2 bytes Voltout = dta%(1) + 256 * dta%(0) 'assume MSB in dta%(0) Volhout Edited 2026-01-01 19:10 by Volhout PicomiteVGA PETSCII ROBOTS |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8412 |
I2C reads bytes. See the I2CREAD command and Appendix B of the manual: I2CREAD addr, option, revlen, revbuf If you want to receive a 16-bit value you will need to set MMBasic up. addr - the address of the chip option - usually 0 to relinquish the bus after use revlen - the number of bytes expected, in this case 2 revbuf - a 1-dimensional array, Rdata() for example or a string You can't receive into a simple numeric variable unless you have revlen set to 1 and are only receiving a single byte. The array will return with the high byte in one element and the low byte in the other. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6420 |
I don't have the INA226 but this is the relevant code I use for the INA3221 FUNCTION INA3221_read(reg AS INTEGER) AS INTEGER LOCAL registers$ I2C2 WRITE ina3221addr,0,1,reg I2C2 READ ina3221addr,0,2,registers$ INA3221_read = STR2BIN(INT16,registers$,BIG) END FUNCTION SUB INA3221_write reg AS INTEGER, value AS INTEGER LOCAL INTEGER hibyte, lobyte lobyte = value AND &hFF hibyte = (value >> 8) AND &hFF I2C2 WRITE ina3221addr,0,3,reg,hibyte,lobyte END SUB Change I2C2 to I2C as required. Jim VK7JH MMedit |
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