Currently I have two undergraduate students who are developing material on interfacing with I2C devices. This includes Dallas Semiconductor DS1621 - Digital Thermometer and Microchip 24LC32 32K EEPROM.
At present, we have have implemented random read and write functions for the EEPROM. Future development will focus routines for sequential reads and writes and and an illustration on how this may be used as an inexpensive data logger. We also plan to look at the new 65K serial EEPROMs.
Another discussion deals with interfacing the 24LC32 with a
The 24LC32 is available in an 8-pin DIP from Digikey (Digikey 32LC32/P-ND). This provides 4K bytes of data storage for a mere $3.00. Note that eight of these may be cascaded on the same two signal leads so as to provide 32 K bytes. Pretty amazing!
The user is referred to
If there are other I2C devices that you would like us to look at, please send me e-mail.
I have just received a grant from the National Science Foundation to continue doing this kind of stuff with my students. If you find this material useful, an entry in my guest book or an e-mail would be greatly appreciated.
' 24LC32.BS2 ' ' Illustrates how to write and read to and from 24LC32 32K EEPROM ' ' BS2 24LC32 ' ' Pin5 (term 10) ------------------- SCL (term 6) ----- To Other ' Pin4 (term 9) -------------------- SDA (term 5) ----- 24LC32 Devices ' ' Note that 10K pullup resistors to +5VDC are required on both signal leads. ' ' Note that the slave address is determined by A2 (term 3), A1 (term2) ' and A0 (term 1) on 24LC32. The above SCL and SDA leads may be multipled ' to eight devices, each strapped for a unique A2 A1 A0 setting. ' ' Debug and Pause statements were included only to see what is going on. ' ' copyright Peter H. Anderson, MSU, March 1, '97 ' address var word ' 000 0000 00000 - 111 1111 1111 device var byte ' device 0-7 dta var byte ' data to program o_byte var byte ' byte to send to memory i_byte var byte ' byte fetched from memory n var byte ' index b var bit ' bit ack_bit var bit SDA_PIN con 4 SCL_PIN con 5 SDA_OUT var out4 SCL_OUT var out5 SDA_IN var in4 SDA_DIR var dir4 OUT con 1 IN con 0 dirs=$f0ff main address=$341 ' program data 55 into address $341 device=0 dta=$55 gosub write_random_data 'write dta to address $341 gosub read_random_data 'read from same location debug hex i_byte stop write_random_data 'writes specified data to specified address agn gosub start o_byte=$a0 | (device << 1) ' 1 0 1 0 a2 a1 a0 0 gosub out_byte gosub nack o_byte= address >> 8 ' high byte of address gosub out_byte gosub nack o_byte= address & $ff ' low byte of address gosub out_byte gosub nack o_byte= dta ' data gosub out_byte gosub nack gosub sstop gosub ack ' ack polling if ack_bit=1 then agn return read_random_data ' reads data from specified address ' returns in variable in_byte gosub start o_byte=$a0 | (device << 1) ' 1 0 1 0 a2 a1 a0 0 gosub out_byte gosub nack o_byte= address >> 8 ' high byte of address gosub out_byte gosub nack o_byte= address & $ff ' low byte of address gosub out_byte gosub nack gosub start o_byte=$a0 | (device << 1) | $01' 1010 a2 a1 a0 1 gosub out_byte gosub nack gosub get_byte gosub nack gosub sstop return out_byte low SDA_PIN for n=0 to 7 b= (o_byte >> 7) & 1 if (b=1) then out_one SDA_DIR=OUT debug "0" _clk high SCL_PIN pause 100 low SCL_PIN pause 100 o_byte=o_byte << 1 next SDA_DIR=IN return out_one SDA_DIR=IN debug "I" goto _clk get_byte SDA_DIR=IN 'input i_byte=0 for n=0 to 7 pause 200 high SCL_PIN pause 200 i_byte=(i_byte << 1) | SDA_IN debug dec SDA_IN low SCL_PIN next SDA_DIR=OUT 'output return nack SDA_DIR=IN ' input just in case ack_bit=1 high SCL_PIN ack_bit=SDA_IN debug "A" debug dec ack_bit debug $0d low SCL_PIN SDA_DIR=OUT ' output return ack debug "POLL" gosub start o_byte=$a0 | (device << 1) gosub out_byte gosub nack return start high SDA_PIN high SCL_PIN debug "START" debug $0d low SDA_PIN 'bring SDA low while clock is high low SCL_PIN return sstop low SDA_PIN high SCL_PIN pause 10 high SDA_PIN 'bring SDA high while clock is high debug "STOP" debug $0d return