fix: don't pull REN up on startup before DMM is online

main.c

@@ -55,12 +55,12 @@
 #define MENU_DOT_INTERVAL_MS 500    // Speed of "..." addition
 #define MENU_COMMIT_DELAY_MS 2400   // Time to hold before entering mode
 #define MENU_SUBLAYER_DELAY_MS 500  // Time to "hover" before dots start
-#define MENU_DEBOUNCE_MS 200        // Button press dead-time
+#define MENU_DEBOUNCE_MS 100        // Button press dead-time
 #define MENU_LOCKOUT_MS 1000  // How long to ignore SRQ for after exiting menu
 
 // Polling
 #define POLL_INTERVAL_MS 100        // 10Hz polling when in Passthrough
-#define DMM_RECOVERY_DELAY_MS 1000  // Backoff if DMM vanishes
+#define DMM_RECOVERY_DELAY_MS 2000  // Backoff if DMM vanishes
 
 // Diode sound
 #define DIODE_TH_SHORT 0.050  // Volts (below this = SHORT)
@@ -1007,7 +1007,6 @@ int gpib_read_byte(uint8_t* data, int* eoi_asserted) {
 
 // Sets up Talker/Listener for data transfer
 int gpib_start_session(uint8_t target_addr, session_mode_t mode) {
-  printf("gpib_start_session\n");
   GPIB_ASSERT(PIN_ATN);
   Delay_Us(1);
 
@@ -1159,30 +1158,41 @@ int gpib_serial_poll(uint8_t addr, uint8_t* status) {
   if (gpib_write_byte(GPIB_CMD_LAD | MY_ADDR, 0) < 0) goto err;
   if (gpib_write_byte(GPIB_CMD_TAD | addr, 0) < 0) goto err;
 
-  // gpib_write_data(0x00);  // Float data lines
+  gpib_write_data(0x00);  // Float data lines
-  // GPIB_ASSERT(PIN_NDAC);  // Busy / Not Accepted
+  GPIB_ASSERT(PIN_NDAC);  // Busy / Not Accepted
-  // GPIB_ASSERT(PIN_NRFD);  // Busy / Not Ready
+  GPIB_ASSERT(PIN_NRFD);  // Busy / Not Ready
-  // Delay_Us(5);
+  GPIB_RELEASE(PIN_ATN);  // Handover to data mode
-
-  // drop ATN to read data
-  GPIB_RELEASE(PIN_ATN);
 
   int eoi;
-  int res = gpib_read_byte(status, &eoi);
+  if (gpib_read_byte(status, &eoi) < 0) {
+    goto err_data;
+  }
 
-  // handshake complete, clean up lines
+  GPIB_ASSERT(PIN_ATN);
+  Delay_Us(1);
+
+  // return to cmd mode
   GPIB_RELEASE(PIN_NRFD);
   GPIB_RELEASE(PIN_NDAC);
 
-  // end seq: ATN -> SPD -> UNT
+  // end seq: SPD -> UNT
-  GPIB_ASSERT(PIN_ATN);
+  gpib_write_byte(GPIB_CMD_SPD, 0);
-  gpib_write_byte(GPIB_CMD_SPD, 0);  // disable spoll
+  gpib_write_byte(GPIB_CMD_UNT, 0);
-  gpib_write_byte(GPIB_CMD_UNT, 0);  // untalk
   GPIB_RELEASE(PIN_ATN);
 
-  return res;
+  return 0;
+
+err_data:
+  // if read failed, assert ATN and release those lines
+  GPIB_ASSERT(PIN_ATN);
+  Delay_Us(1);
+  GPIB_RELEASE(PIN_NRFD);
+  GPIB_RELEASE(PIN_NDAC);
 
 err:
+  // just ensure we don't leave the device in spoll mode
+  gpib_write_byte(GPIB_CMD_SPD, 0);
+  gpib_write_byte(GPIB_CMD_UNT, 0);
   GPIB_RELEASE(PIN_ATN);
   return -1;
 }
@@ -1334,18 +1344,14 @@ int gpib_receive_binary(uint8_t addr, char* buf, int expected_len) {
 }
 
 void gpib_init(void) {
-  // configure control lines as open-drain outputs
+  // calculate BSHR for the DIO lines
-  funPinMode(PIN_EOI, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+  for (int i = 0; i < 256; i++) {
-  funPinMode(PIN_REN, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+    gpib_write_lut[i] =
-  funPinMode(PIN_ATN, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+        CALC_PIN_BSHR(i, 0, PIN_POS_D1) | CALC_PIN_BSHR(i, 1, PIN_POS_D2) |
-  funPinMode(PIN_IFC, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+        CALC_PIN_BSHR(i, 2, PIN_POS_D3) | CALC_PIN_BSHR(i, 3, PIN_POS_D4) |
-  funPinMode(PIN_DAV, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+        CALC_PIN_BSHR(i, 4, PIN_POS_D5) | CALC_PIN_BSHR(i, 5, PIN_POS_D6) |
-  funPinMode(PIN_NDAC, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+        CALC_PIN_BSHR(i, 6, PIN_POS_D7) | CALC_PIN_BSHR(i, 7, PIN_POS_D8);
-  funPinMode(PIN_NRFD, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+  }
-
-  // SRQ is input with pull-up
-  funPinMode(PIN_SRQ, GPIO_CNF_IN_PUPD);
-  funDigitalWrite(PIN_SRQ, 1);
 
   // float all control lines
   GPIB_RELEASE(PIN_EOI);
@@ -1356,6 +1362,18 @@ void gpib_init(void) {
   GPIB_RELEASE(PIN_NDAC);
   GPIB_RELEASE(PIN_NRFD);
 
+  // configure control lines as open-drain outputs
+  funPinMode(PIN_EOI, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+  funPinMode(PIN_REN, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+  funPinMode(PIN_ATN, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+  funPinMode(PIN_IFC, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+  funPinMode(PIN_DAV, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+  funPinMode(PIN_NDAC, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+  funPinMode(PIN_NRFD, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
+
+  // float data lines
+  gpib_write_data(0x00);
+
   // data lines
   funPinMode(PIN_DIO1, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
   funPinMode(PIN_DIO2, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
@@ -1366,17 +1384,12 @@ void gpib_init(void) {
   funPinMode(PIN_DIO7, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
   funPinMode(PIN_DIO8, GPIO_Speed_50MHz | GPIO_CNF_OUT_OD);
 
-  // calculate BSHR for the DIO lines
+  // SRQ is input with pull-up
-  for (int i = 0; i < 256; i++) {
+  funPinMode(PIN_SRQ, GPIO_CNF_IN_PUPD);
-    gpib_write_lut[i] =
+  funDigitalWrite(PIN_SRQ, 1);
-        CALC_PIN_BSHR(i, 0, PIN_POS_D1) | CALC_PIN_BSHR(i, 1, PIN_POS_D2) |
-        CALC_PIN_BSHR(i, 2, PIN_POS_D3) | CALC_PIN_BSHR(i, 3, PIN_POS_D4) |
-        CALC_PIN_BSHR(i, 4, PIN_POS_D5) | CALC_PIN_BSHR(i, 5, PIN_POS_D6) |
-        CALC_PIN_BSHR(i, 6, PIN_POS_D7) | CALC_PIN_BSHR(i, 7, PIN_POS_D8);
-  }
 
-  // float data lines
+  // clr
-  gpib_write_data(0x00);
+  gpib_interface_clear();
 }
 
 // ------------------------------------
@@ -2297,7 +2310,8 @@ void handle_menu_navigation(void) {
     // only poll GPIB if physical line is asserted
     if (gpib_check_srq()) {
       uint8_t stb = 0;
-      gpib_serial_poll(app.dmm_addr, &stb);
+
+      if (gpib_serial_poll(app.dmm_addr, &stb) != 0) return;
 
       // check if it was the front panel btn
       if (stb & HP3478A_MASK_KEYBOARD_SRQ) {
@@ -2429,7 +2443,6 @@ void app_loop(void) {
       if (app.dmm_online) {
         // printf("DMM Lost connection.\n");
         app.dmm_online = 0;
-        gpib_interface_clear();
       }
       // slow down polling when offline
       app.poll_interval = DMM_RECOVERY_DELAY_MS;
@@ -2439,6 +2452,10 @@ void app_loop(void) {
     // got a valid response, check if this is a recovery
     if (!app.dmm_online) {
       // printf("DMM Recovered.\n");
+      // only assert REN here when it's online
+      gpib_remote_enable(1);
+      gpib_interface_clear();
+
       app.dmm_online = 1;
       gpib_send(app.dmm_addr, HP3478A_CMD_MASK_BTN_ONLY HP3478A_CMD_SRQ_CLEAR);
       gpib_go_to_local(app.dmm_addr);
@@ -2894,7 +2911,6 @@ int main() {
 
   // GPIB controller
   gpib_init();
-  gpib_remote_enable(1);
 
   // USB interface
   USBFSSetup();