Hi,
I'm trying to use the SCAN mode of max1239 but can't get expected result.
from table 1 and 2, we set our configuration byte as 03(SCAN up to channel 1) or 05 (SCAN UP TO channel 6) and setup byte as F2.
The setup and config byte are sent out correctly on the bus as shown.
However, when we enable read with slave address with read bit set as in attached I2C bus capture, no matter the config byte is 03 or 05, it is always sending 5 readings of channel 0 and not as the the figure 10 in datasheet.
Looking at the msg sent on the bus, is there something we missed? Thanks.
Table 1: Setup Byte Description
|
Bit |
Name |
Description |
|
7 |
REG |
Register bit. 1 = setup byte, 0 = configuration byte |
|
6 |
SEL2 |
Three bits select the reference voltage and the state of AIN_/REF. Default to 000 at power-up |
|
5 |
SEL1 |
|
|
4 |
SEL0 |
|
|
3 |
CLK |
1 = external clock, 0 = internal clock. Default to 0 at power-up. |
|
2 |
BIP/UNI |
1 = bipolar, 0 = unipolar. Default to 0 at power-up (see the Unipolar/Bipolar section). |
|
1 |
RST |
1= no action, 0 = resets the configuration register to default. Setup register remains unchanged. |
|
0 |
X |
Don’t care. |
Table 2: Configuration Byte Description
|
Bit |
Name |
Description |
|
7 |
REG |
Register bit. 1 = setup byte, 0 = configuration byte |
|
6 |
SCAN1 |
Scan select bits. Two bits select the scanning configuration (Table 3). Default to 00 at power-up. |
|
5 |
SCAN0 |
|
|
4 |
CS3 |
Channel select bits. Four bits select which analog input channels are to be used for conversion. Default to 0000 at power-up. Valid values are 0000 (AIN0) to 1011 (AIN11). For our VDB application, valid values up till 1001 (AIN9); AIN10/11 not used. |
|
3 |
CS2 |
|
|
2 |
CS1 |
|
|
1 |
CS0 |
|
|
0 |
SGL/DIF |
1 = single-ended, 0 = differential. We do not need differential mode. Default to 1 at power-up. |
Thanks
Yiqi
