AM2634: SDK Examples for differential ADC do not work with ADC0 AIN0-AIN1

Daniel Brown

Part Number: AM2634
Other Parts Discussed in Thread: TMDSHSECDOCK, TMDSCNCD263, SYSCONFIG

I ran the example from the SDK 8.06: adc_differential_mode_am263x-cc_r5fss0-0_nortos_ti-arm-clang

I wanted to check ADC0 AIN0 and AIN1. I put a jumper on the TMDSHSECDOCK docking board pins 9 and 11 to ground it out. It should read 2112 for all measurements. This is what I get:

[Cortex_R5_0] ADC Differential Mode Test Started ...
ADC0
SOC0    :   SOC1
1984 :   2343
1577 :   2640
1594 :   2627
1594 :   2628
1587 :   2632
1601 :   2666
1603 :   2621
1602 :   2621
1602 :   2621
1588 :   2632
1602 :   2621
ADC Differential Mode Test Passed
All tests have passed!!

I am using the TMDSCNCD263 control card, PCB# PROC110E2. The AM263x Control Card Hardware User's Guide Table 4-18 mentions a MUX Select Signal ADC1_MUX_SEL. Maybe all I need to do is change that, but it doesn't explain how. Is it something with I2C? If so, how do I do it?

I have tested a number of other ADC channels and they work properly (ADC0 AIN2-AIN3, etc.)

over 2 years ago

0 Zain Nasir over 2 years ago

Expert 1330 points

In the case of the AM263x Control Card, the ADC multiplexer (MUX) select signals are controlled through software, not I2C. To configure the ADC MUX for differential mode on ADC0 AIN0 and AIN1, you may need to modify the code to set the appropriate MUX configuration (if you already have to done that.)

0 Daniel Brown over 2 years ago in reply to Zain Nasir

Prodigy 145 points

The issue is not getting differential mode working. I use sysconfig, and and it works with ADC0 AIN2 and AIN3. The issue is that the HSEC pins are connected to ADC0 AIN0 and AIN1 go through a mux before they even get to the AM263x chip. However ADC0 AIN2 and AIN3 are directly connected to the HSEC pins. How do I tell the control card which signal to route to the HSEC pin?

0 Daniel Brown over 2 years ago

Prodigy 145 points

I would love to have some example code that sets ADC1_MUX_SEL, much like this example that was used to select UART instead of LIN in the IO Expander.
https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1234850/tmdscncd263-how-to-generate-uart-commands-using-uart1-through-docking-station/4665253?tisearch=e2e-sitesearch&keymatch=TMDSCNCD263%20mux#4665253

Which was shown in a snippet of the schematic (not sure where the whole thing is):

https://e2e.ti.com/support/microcontrollers/arm-based-microcontrollers-group/arm-based-microcontrollers/f/arm-based-microcontrollers-forum/1190530/tmdscncd263-am263-control-card-how-to-set-lin_mux_sel-high/4488435?tisearch=e2e-sitesearch&keymatch=TMDSCNCD263%2520mux#4488435

0 Daniel Brown over 2 years ago in reply to Daniel Brown

Prodigy 145 points

I had some off-line help with the IO expander setup using I2C. I think this is the critical portion of code:

uint8_t reg_command_out1 = 0x03;

        /* set the port 1, bit 6 output high*/
        i2cTransaction.writeBuf   = txBuffer;
        i2cTransaction.writeCount = 2;
        txBuffer[0] = reg_command_out1;
        txBuffer[1] = port1_out1; // turn port 1, bit 6 to output, keep everything else default input
        status = I2C_transfer(i2cHandle, &i2cTransaction);

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AM2634: SDK Examples for differential ADC do not work with ADC0 AIN0-AIN1