I think the clue is in the word errata. This is obviously a hardware bug that effects some ADC modules. If the Pic your using doesn't mention an errata sheet in the ADC section then I wouldn't worry about it. As you say, initialise it once and then just set the GO bit.MrNobody said:Below is part of the ADC code i found in microchip's TCP/IP stack.. I am trying to understand the reason why the code is written that way..
First question i have is regarding the "#if !defined(__18F452)" macro. Why does the code assign ADCON2 to PRODL, and after that make changes to ADCON followed by assigning PRODL back to ADCON2..?Code:
// AN0 should already be set up as an analog input ADCON0bits.GO = 1; // Wait until A/D conversion is done while(ADCON0bits.GO); // AD converter errata work around (ex: PIC18F87J10 A2) #if !defined(__18F452) PRODL = ADCON2; ADCON2bits.ADCS0 = 1; ADCON2bits.ADCS1 = 1; ADCON2 = PRODL; #endif // Convert 10-bit value into ASCII string itoa(*((WORD*)(&ADRESL)), AN0String);
Won't that overwrite the changes made in the middle..?
Second question is, these lines are part of a function that was called everytime the ADC need to sample the signal. Why does the ADC needs to be reinitialized everytime before the sample is taken..? I mean, why not just do it like below..?
Is there any benefit in reinitializing the ADC before taking the samples..? Even in 18F4620's datasheet on page 227, it ask to reconfigure A/D module everytime before taking the sample (Step 7 which ask to go back to Step 1 or Step 2).Code:
// Wait until A/D conversion is done while(ADCON0bits.GO); // Convert 10-bit value into ASCII string itoa(*((WORD*)(&ADRESL)), AN0String);