diff --git a/tests/simm_electrical_test.c b/tests/simm_electrical_test.c index 3b30480..94c79d3 100644 --- a/tests/simm_electrical_test.c +++ b/tests/simm_electrical_test.c @@ -43,6 +43,7 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t)) Ports_Init(); + // Give everything a bit of time to settle down DelayMS(DELAY_SETTLE_TIME_MS); // First check for anything shorted to ground. Set all lines as inputs with a weak pull-up resistor. @@ -60,73 +61,80 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t)) DelayMS(DELAY_SETTLE_TIME_MS); - uint8_t testPinFailIndex; - uint8_t failIndex; + uint8_t curPin = 0; + uint8_t i; + + // Read the address pins back first of all uint32_t readback = Ports_ReadAddress(); if (readback != SIMM_ADDRESS_PINS_MASK) { - failIndex = FIRST_ADDRESS_LINE_FAIL_INDEX; - - // At this point, any errors will manifest as 0 bits. It's easier to test for errors by turning them - // into 1 bits, so invert the readback -- now, shorted pins are 1s and non-shorted pins are 0s - readback = ~readback & SIMM_ADDRESS_PINS_MASK; - - // As long as there are any 1 bits, there is a short detected. - while (readback) + // Check each bit for a LOW which would indicate a short to ground + for (i = 0; i <= SIMM_HIGHEST_ADDRESS_LINE; i++) { - if (readback & 1) // failure here? + // Did we find a low bit? + if (!(readback & 1)) { - errorHandler(failIndex, GROUND_FAIL_INDEX); - SIMMElectricalTest_AddGroundShort(failIndex); + // That means this pin is shorted to ground. + // So notify the caller that we have a ground short on this pin + errorHandler(curPin, GROUND_FAIL_INDEX); + + // Add it to our internal list of ground shorts also. + SIMMElectricalTest_AddGroundShort(curPin); + + // And of course increment the error counter. numErrors++; } + // No matter what, though, move on to the next bit and pin. readback >>= 1; - failIndex++; + curPin++; } } + // Repeat the exact same process for the data pins readback = Ports_ReadData(); if (readback != SIMM_DATA_PINS_MASK) { - failIndex = FIRST_DATA_LINE_FAIL_INDEX; - - readback = ~readback; - - while (readback) + for (i = 0; i <= SIMM_HIGHEST_DATA_LINE; i++) { - if (readback & 1) // failure here? + if (!(readback & 1)) // failure here? { - errorHandler(failIndex, GROUND_FAIL_INDEX); - SIMMElectricalTest_AddGroundShort(failIndex); + errorHandler(curPin, GROUND_FAIL_INDEX); + SIMMElectricalTest_AddGroundShort(curPin); numErrors++; } readback >>= 1; - failIndex++; + curPin++; } } + // Check chip select in the same way... if (!Ports_ReadCS()) { - errorHandler(CS_FAIL_INDEX, GROUND_FAIL_INDEX); - SIMMElectricalTest_AddGroundShort(CS_FAIL_INDEX); + errorHandler(curPin, GROUND_FAIL_INDEX); + SIMMElectricalTest_AddGroundShort(curPin); numErrors++; } + curPin++; + // Output enable... if (!Ports_ReadOE()) { - errorHandler(OE_FAIL_INDEX, GROUND_FAIL_INDEX); - SIMMElectricalTest_AddGroundShort(OE_FAIL_INDEX); + errorHandler(curPin, GROUND_FAIL_INDEX); + SIMMElectricalTest_AddGroundShort(curPin); numErrors++; } + curPin++; + // Write enable... if (!Ports_ReadWE()) { - errorHandler(WE_FAIL_INDEX, GROUND_FAIL_INDEX); - SIMMElectricalTest_AddGroundShort(WE_FAIL_INDEX); + errorHandler(curPin, GROUND_FAIL_INDEX); + SIMMElectricalTest_AddGroundShort(curPin); numErrors++; } + curPin++; // Doesn't need to be here, but for consistency I'm leaving it. // OK, now we know which lines are shorted to ground. // We need to keep that in mind, because those lines will now show as shorted @@ -134,12 +142,10 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t)) // Now, check each individual line vs. all other lines on the SIMM for any shorts between them ElectricalTestStage curStage = TestingAddressLines; - int x = 0; - // This is a counter we do once per pin. I use it to do a "triangle" algorithm so that I don't check - // every possible pair of pins twice. If I did, I would get two notifications for each short. - uint8_t pinsAlreadyChecked = 0; - uint8_t thisPin = 0; - uint8_t i; + int x = 0; // Counter of what address or data pin we're on. Not used for control lines. + uint8_t testPin = 0; // What pin we are currently testing all other pins against. + // x is only a counter inside the address or data pins. + // testPin is a total counter of ALL pins. while (curStage != DoneTesting) { // Set one pin to output a 0. @@ -147,12 +153,11 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t)) // Then read back all the other pins. If any of them read back as 0, // it means they are shorted to the pin we set as an output. - // This is the fail index of the pin we are outputting a 0 on. - testPinFailIndex = 0xFE; // Start with a default invalid value...will be replaced though. - + // If we're testing address lines right now, set the current address line + // as an output (and make it output a LOW). + // Set all other address lines as inputs with pullups. if (curStage == TestingAddressLines) { - testPinFailIndex = FIRST_ADDRESS_LINE_FAIL_INDEX + x; // fail index of this address line uint32_t addressLineMask = (1UL << x); // mask of the address pin we're testing Ports_SetAddressDDR(addressLineMask); // set it as an output and all other address pins as inputs @@ -167,10 +172,9 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t)) Ports_AddressPullups_RMW(SIMM_ADDRESS_PINS_MASK, SIMM_ADDRESS_PINS_MASK); } - + // Do the same thing for data lines... if (curStage == TestingDataLines) { - testPinFailIndex = FIRST_DATA_LINE_FAIL_INDEX + x; uint32_t dataLineMask = (1UL << x); Ports_SetDataDDR(dataLineMask); Ports_DataOut_RMW(0, dataLineMask); @@ -182,9 +186,9 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t)) Ports_DataPullups_RMW(SIMM_DATA_PINS_MASK, SIMM_DATA_PINS_MASK); } + // Chip select... if (curStage == TestingCS) { - testPinFailIndex = CS_FAIL_INDEX; Ports_SetCSDDR(true); Ports_SetCSOut(false); } @@ -194,9 +198,9 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t)) Ports_SetCSPullup(true); } + // Output enable... if (curStage == TestingOE) { - testPinFailIndex = OE_FAIL_INDEX; Ports_SetOEDDR(true); Ports_SetOEOut(false); } @@ -206,9 +210,9 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t)) Ports_SetOEPullup(true); } + // And write enable. if (curStage == TestingWE) { - testPinFailIndex = WE_FAIL_INDEX; Ports_SetWEDDR(true); Ports_SetWEOut(false); } @@ -221,101 +225,85 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t)) // OK, so now we have set up all lines as needed. Exactly one pin is outputting a 0, and all other pins // are inputs with pull-ups enabled. Read back all the lines, and if any pin reads back as 0, // it means that pin is shorted to the pin we are testing (overpowering its pullup) + // However, because we test each pin against every other pin, any short would appear twice. + // Once as "pin 1 is shorted to pin 2" and once as "pin 2 is shorted to pin 1". To avoid + // that annoyance, I only check each combination of two pins once. You'll see below + // how I do this by testing to ensure curPin > testPin. DelayMS(DELAY_SETTLE_TIME_MS); - // Now keep a count of how many pins we have actually checked. - // We will skip the first "pinsAlreadyChecked" pins each time so we don't get duplicates. - thisPin = 0; + // Now keep a count of how many pins we have actually checked during THIS test. + curPin = 0; // Read back the address data to see if any shorts were found readback = Ports_ReadAddress(); - if (curStage == TestingAddressLines) - { - // Insert a high bit so our test doesn't fail on the pin we were testing - readback |= (1UL << x); - } - - failIndex = FIRST_ADDRESS_LINE_FAIL_INDEX; // Count any shorted pins for (i = 0; i <= SIMM_HIGHEST_ADDRESS_LINE; i++) { // failure here? - if ((thisPin >= pinsAlreadyChecked) && // We haven't already checked this combination of pins... - !(readback & 1) && // It's showing as a short... - !SIMMElectricalTest_IsGroundShort(failIndex)) // And it's not a short to ground + if ((curPin > testPin) && // We haven't already checked this combination of pins (don't test pin against itself either) + !(readback & 1) && // It's showing as low (which indicates a short) + !SIMMElectricalTest_IsGroundShort(curPin)) // And it's not recorded as a short to ground { - errorHandler(testPinFailIndex, failIndex); + // Send it out as an error notification and increase error counter + errorHandler(testPin, curPin); numErrors++; } + // No matter what, move on to the next bit and pin readback >>= 1; - failIndex++; - thisPin++; + curPin++; } + // Same thing for data pins readback = Ports_ReadData(); - if (curStage == TestingDataLines) - { - // Insert a high bit so our test doesn't fail on the pin we were testing - readback |= (1UL << x); - } - - failIndex = FIRST_DATA_LINE_FAIL_INDEX; // Count any shorted pins - while (readback) + for (i = 0; i <= SIMM_HIGHEST_DATA_LINE; i++) { // failure here? - if ((thisPin >= pinsAlreadyChecked) && // We haven't already checked this combination of pins... - !(readback & 1) && // It's showing as a short... - !SIMMElectricalTest_IsGroundShort(failIndex)) // And it's not a short to ground + if ((curPin > testPin) && // We haven't already checked this combination of pins (don't test pin against itself either) + !(readback & 1) && // It's showing as low (which indicates a short) + !SIMMElectricalTest_IsGroundShort(curPin)) // And it's not recorded as a short to ground { - errorHandler(testPinFailIndex, failIndex); + errorHandler(testPin, curPin); numErrors++; } readback >>= 1; - failIndex++; - thisPin++; + curPin++; } - if (curStage != TestingCS) + // And chip select... + if ((curPin > testPin) && + !Ports_ReadCS() && + !SIMMElectricalTest_IsGroundShort(curPin)) { - if ((thisPin >= pinsAlreadyChecked) && - !Ports_ReadCS() && - !SIMMElectricalTest_IsGroundShort(CS_FAIL_INDEX)) - { - errorHandler(testPinFailIndex, CS_FAIL_INDEX); - numErrors++; - } + errorHandler(testPin, curPin); + numErrors++; } - thisPin++; + curPin++; - if (curStage != TestingOE) + // Output enable... + if ((curPin > testPin) && + !Ports_ReadOE() && + !SIMMElectricalTest_IsGroundShort(curPin)) { - if ((thisPin >= pinsAlreadyChecked) && - !Ports_ReadOE() && - !SIMMElectricalTest_IsGroundShort(OE_FAIL_INDEX)) - { - errorHandler(testPinFailIndex, OE_FAIL_INDEX); - numErrors++; - } + errorHandler(testPin, curPin); + numErrors++; } - thisPin++; + curPin++; - if (curStage != TestingWE) + // And write enable + if ((curPin > testPin) && + !Ports_ReadWE() && + !SIMMElectricalTest_IsGroundShort(curPin)) { - if ((thisPin >= pinsAlreadyChecked) && - !Ports_ReadWE() && - !SIMMElectricalTest_IsGroundShort(WE_FAIL_INDEX)) - { - errorHandler(testPinFailIndex, WE_FAIL_INDEX); - numErrors++; - } + errorHandler(testPin, curPin); + numErrors++; } - thisPin++; + curPin++; // Not needed, kept for consistency // Finally, move on to the next stage if needed. if (curStage == TestingAddressLines) @@ -342,8 +330,8 @@ int SIMMElectricalTest_Run(void (*errorHandler)(uint8_t, uint8_t)) curStage++; } - // Increase the number of pins we have actually checked... - pinsAlreadyChecked++; + // Move on to test the next pin + testPin++; } return numErrors;